A phase 3 randomized, open-label study evaluating the immunogenicity and safety of concomitant and staggered administration of a live, pentavalent rotavirus vaccine and an inactivated poliomyelitis vaccine in healthy infants in China.

This open-label, randomized, phase 3 study in China (V260-074; NCT04481191) evaluated the immunogenicity and safety of concomitant and staggered administration of three doses of an oral, live, pentavalent rotavirus vaccine (RV5) and three doses of an intramuscular, inactivated poliomyelitis vaccine (IPV) in 400 healthy infants. The primary objective was the non-inferiority of neutralizing antibody (nAb) responses in the concomitant- versus the staggered-use groups. Antibody responses were measured at baseline and 1-month post-dose 3 (PD3). Parents/legal guardians recorded adverse events for 30 or 15 d after study vaccinations in the concomitant-use or staggered-use groups, respectively. At PD3, >98% of participants seroconverted to all three poliovirus types, and the primary objective was met as lower bounds of the two-sided 95% CI for between-group difference in nAb seroconversion percentages ranged from - 4.3% to - 1.6%, for all poliovirus types, p < .001. At PD3, geometric mean titers (GMTs) of nAb responses to poliovirus types 1, 2, and 3 in the concomitant-use group and the staggered-use group were comparable; 100% of participants had nAb titers ≥1:8 and ≥1:64 for all poliovirus types. Anti-rotavirus serotype-specific IgA GMTs and participants with ≥3-fold rise in postvaccination titers from baseline were comparable between groups. Administration of RV5 and IPV was well tolerated with comparable safety profiles in both groups. The immunogenicity of IPV in the concomitant-use group was non-inferior to the staggered-use group and RV5 was immunogenic in both groups. No safety concerns were identified. These data support the concomitant use of RV5 and IPV in healthy Chinese infants.

Immune persistence after different polio sequential immunization schedules in Chinese infants.

Trivalent oral poliovirus vaccine (tOPV) has been withdrawn and instead an inactivated poliovirus vaccine (IPV) and bivalent type 1 and type 3 OPV (bOPV) sequential immunization schedule has been implemented since 2016, but no immune persistence data are available for this polio vaccination strategy. This study aimed to assess immune persistence following different polio sequential immunization schedules. Venous blood was collected at 24, 36, and 48 months of age from participants who had completed sequential schedules of combined IPV and OPV in phase III clinical trials. The serum neutralizing antibody titers against poliovirus were determined, and the poliovirus-specific antibody-positive rates were evaluated. A total of 1104 participants were enrolled in this study. The positive rates of poliovirus type 1- and type 3-specific antibodies among the sequential immunization groups showed no significant difference at 24, 36, or 48 months of age. The positive rates of poliovirus type 2-specific antibody in the IPV-IPV-tOPV group at all time points were nearly 100%, which was significantly higher than the corresponding rates in other immunization groups (IPV-bOPV-bOPV and IPV-IPV-bOPV). Immunization schedules involving one or two doses of IPV followed by bOPV failed to maintain a high positive rate for poliovirus type 2-specific antibody.

Quantitative Analysis of the Instant and Persistent Inhibition Effects of Maternal Poliovirus Antibodies on the Immune Response in a Phase IV Trial of a Sabin Strain-Based Inactivated Poliovirus Vaccine.

BACKGROUND: An inactivated poliomyelitis vaccine made from Sabin strains (sIPVs) has widely been used in China since 2015. However, the quantitative data on the instant and persistent inhibition effects of maternal poliovirus antibodies on the immune response to sIPV priming and booster vaccination have not been available yet. OBJECTIVE: In this study, we aim to explore and quantify the instant and persistent inhibition effect of maternal poliovirus antibodies on the immune response elicited by sIPV primary and booster vaccination. METHODS: The immunogenicity data consisting of the days 0 and 30 after the prime and booster vaccination of the sIPV in a phase IV trial were pooled for a quantitative analysis of the inhibition effect of maternal poliovirus antibody. The geometric mean ratio (GMR) was calculated using linear regression models, representing that every 2-fold higher maternal poliovirus antibody titer may result in a (1-GMR) lower postimmunization antibody titer. RESULTS: The GMRs for poliovirus types 1, 2, and 3 were 0.79 (0.77-0.82), 0.85 (0.81-0.89), and 0.87 (0.83-0.91) at 30 days after the priming series, 0.86 (0.83-0.89), 0.81 (0.76-0.85), and 0.86 (0.80-0.93) at one year after the priming series, and 0.96 (0.94-0.99), 0.89 (0.86-0.93), and 0.98 (0.93-1.03) at 30 days after the booster dose. The inhibition effect continued to exist until the booster dose 1 year later, and such a persistent inhibition effect was almost attenuated for poliovirus types 1 and 3, and partly reduced for type 2 at 30 days after the booster dose. CONCLUSION: A wider interval between the four sIPV doses might be a consideration for reducing the effect of maternal antibodies and subsequently eliciting and maintaining higher antibody levels to protect against poliovirus transmission and infection at the final stage of polio eradication in the global world. This study's clinical trial registry number is NCT04224519.

Immunogenicity and lot-to-lot consistency of booster shot with Sabin inactivated poliomyelitis vaccine in Chinese children aged 18-24 Months: A phase â £ clinical trial.

BACKGROUND: There has been no data on the immunogenicity and safety of the 4th booster dose of the sIPV immunization in 18-24 months old children in post-marketing studies of large cohort providing with robust results. METHOD: In a phase Ⅳ randomized, double-blinded clinical trial, 1200 participants aged 2 months were immunized with three consecutive doses of sIPV at 2, 3, and 4 months old to complete primary immunization. Out of the 1200 participants, 1129 received the 4th dose of sIPV as booster immunization. Immunogenicity was evaluated in 1100 participants. RESULTS: Seropositive rates of the anti-poliovirus type 1, 2, and 3 neutralizing antibodies were 99.9 %, 98.0 %, 98.2 %, respectively, with GMTs of 557.0, 146.1, 362.0 one year after primary vaccination. After booster vaccination between 18 and 24 months old, the seropositive rates for 3 types all reached 100.0 %, with GMTs of 8343.6, 5039.6, 5492.0, respectively. Particularly for the anti-poliovirus type 2 antibody, the GMT was 230.4 after primary immunization, maintained to 146.1 one year after primary immunization, and increased to as high as 5039.6 after booster vaccination. The GMT ratios between each batch groups after booster immunization were between 0.67 and 1.50, meeting the immunological equivalence criteria. The incidence rate of adverse reaction was 23.0 %, which was comparable to those in the phase Ⅲ trial but had a lower incidence. Furthermore, no SUSAR was reported in this study. INTERPRETATION: In conclusion, as the anti-poliovirus antibodies gradually waned one year post sIPV primary vaccination, especially the type 2 antibody waned to a very low level, suggesting the importance of the booster immunization for children at the age of 18-24 months old. The booster shot can greatly enhance the antibody level and protect children from the potential risk of infection with WPV and VDPV by supplementing the anti-poliovirus type 2 immunity gap in the current real world. Clinic Trial Registration. NCT04224519.

Immune persistence of an inactivated poliovirus vaccine derived from the Sabin strain: a 10-year follow-up of a phase 3 study.

Background: In a previous phase 3 clinical trial, we showed that an inactivated poliovirus vaccine derived from the Sabin strain (sIPV) can induce neutralising antibodies against currently circulating and reference wild poliovirus strains. However, the immune persistence of sIPV remains to be evaluated. Methods: In this study, 400 participants who were eligible for an early phase 3 clinical trial (Jan 1, 2012-Aug 31, 2014) in Pingle County, GuanXi Province, China, were initially involved in one site. Of the participants in the previous phase 3 clinical trial, sera of 287, 262, 237, and 207 participants were sampled at the ages of 4, 6, 8, and 10 years, respectively, after the prime-boost regimen. Neutralising antibodies against attenuated Sabin strains were detected using these serum samples to determine immune persistence. The serum neutralising antibodies titre of 1:8 against poliovirus types 1, 2, and 3 is considered to be a seroprotection level for polio. The trial is registered at ClinicalTrials.gov, NCT01510366. Findings: The protective rates against poliovirus types 1, 2, and 3 in the sIPV group were all 100% at 10 years after the booster immunisation, compared with 98.1%, 100%, and 97.1%, respectively, in the wIPV control group after 10 years. After the booster at 18 months, the geometric mean titres (GMTs) of neutralising antibodies against poliovirus types 1, 2, and 3 in the sIPV group were 13,265.6, 7856.7, and 6432.2, respectively, and the GMTs in the control group (inoculated with inactivated poliovirus vaccine derived from wild strain (wIPV)) were 3915.6, 2842.6, and 4982.7, respectively. With increasing time after booster immunisation, the GMTs of neutralising antibodies against poliovirus types 1, 2, and 3 gradually decreased in both the sIPV and wIPV groups. At the age of ten years, the GMTs of neutralising antibodies against poliovirus types 1, 2, and 3 in the sIPV group were 452.3, 392.8, and 347.5, respectively, and the GMTs in the wIPV group 108.5, 154.8, and 229.3, respectively, which were still at a higher-than-protective level (1:8). Interpretation: Both sIPV and wIPV maintained sufficiently high immune persistence against poliovirus types 1, 2, and 3 for at least 10 years after booster immunisation. Funding: Yunnan Provincial Science and Technology Department, the Bill and Melinda Gates Foundation, the National High-tech Research and Development Program, the National International Science and Technology Cooperation Project, the Yunnan Application Basic Research Project, the Innovation Team Project of Xie He, the Yunnan International Scientific and Technological Cooperation Project, and the Medical and Technology Innovation Project of Xie He.

Heterologous prime-boost immunisation with mRNA- and AdC68-based 2019-nCoV variant vaccines induces broad-spectrum immune responses in mice.

The ongoing evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or 2019-nCoV) variants has been associated with the transmission and pathogenicity of COVID-19. Therefore, exploring the optimal immunisation strategy to improve the broad-spectrum cross-protection ability of COVID-19 vaccines is of great significance. Herein, we assessed different heterologous prime-boost strategies with chimpanzee adenovirus vector-based COVID-19 vaccines plus Wuhan-Hu-1 (WH-1) strain (AdW) and Beta variant (AdB) and mRNA-based COVID-19 vaccines plus WH-1 strain (ARW) and Omicron (B.1.1.529) variant (ARO) in 6-week-old female BALB/c mice. AdW and AdB were administered intramuscularly or intranasally, while ARW and ARO were administered intramuscularly. Intranasal or intramuscular vaccination with AdB followed by ARO booster exhibited the highest levels of cross-reactive IgG, pseudovirus-neutralising antibody (PNAb) responses, and angiotensin-converting enzyme-2 (ACE2)-binding inhibition rates against different 2019-nCoV variants among all vaccination groups. Moreover, intranasal AdB vaccination followed by ARO induced higher levels of IgA and neutralising antibody responses against live 2019-nCoV than intramuscular AdB vaccination followed by ARO. A single dose of AdB administered intranasally or intramuscularly induced broader cross-NAb responses than AdW. Th1-biased cellular immune response was induced in all vaccination groups. Intramuscular vaccination-only groups exhibited higher levels of Th1 cytokines than intranasal vaccination-only and intranasal vaccination-containing groups. However, no obvious differences were found in the levels of Th2 cytokines between the control and all vaccination groups. Our findings provide a basis for exploring vaccination strategies against different 2019-nCoV variants to achieve high broad-spectrum immune efficacy.

Safety and immunogenicity of a protein subunit COVID-19 vaccine (ZF2001) in healthy children and adolescents aged 3-17 years in China: a randomised, double-blind, placebo-controlled, phase 1 trial and an open-label, non-randomised, non-inferiority, phase 2 trial.

BACKGROUND: ZF2001 is a recombinant protein subunit vaccine against SARS-CoV-2 that has been approved for use in China, Colombia, Indonesia, and Uzbekistan in adults aged 18 years or older, but not yet in children and adolescents younger than 18 years. We aimed to evaluate the safety and immunogenicity of ZF2001 in children and adolescents aged 3-17 years in China. METHODS: The randomised, double-blind, placebo-controlled, phase 1 trial and the open-label, non-randomised, non-inferiority, phase 2 trial were done at the Xiangtan Center for Disease Control and Prevention (Hunan Province, China). Healthy children and adolescents aged 3-17 years, without a history of SARS-CoV-2 vaccination, without a history of COVID-19, without COVID-19 at the time of the study, and without contact with patients with confirmed or suspected COVID-19 were included in the phase 1 and phase 2 trials. In the phase 1 trial, participants were divided into three groups according to age (3-5 years, 6-11 years, and 12-17 years). Each group was randomly assigned (4:1), using block randomisation with five blocks, each with a block size of five, to receive three 25 µg doses of the vaccine, ZF2001, or placebo intramuscularly in the arm 30 days apart. The participants and investigators were masked to treatment allocation. In the phase 2 trial, participants received three 25 µg doses of ZF2001 30 days apart and remained stratified by age group. For phase 1, the primary endpoint was safety and the secondary endpoint was immunogenicity (humoral immune response on day 30 after the third vaccine dose: geometric mean titre [GMT] of prototype SARS-CoV-2 neutralising antibodies and seroconversion rate, and geometric mean concentration [GMC] of prototype SARS-CoV-2 receptor-binding domain [RBD]-binding IgG antibodies and seroconversion rate). For phase 2, the primary endpoint was the GMT of SARS-CoV-2 neutralising antibodies with seroconversion rate on day 14 after the third vaccine dose, and the secondary endpoints included the GMT of RBD-binding antibodies and seroconversion rate on day 14 after the third vaccine dose, the GMT of neutralising antibodies against the omicron BA.2 subvariant and seroconversion rate on day 14 after the third vaccine dose, and safety. Safety was analysed in participants who received at least one dose of the vaccine or placebo. Immunogenicity was analysed in the full-analysis set (ie, participants who received at least one dose and had antibody results) by intention to treat and in the per-protocol set (ie, participants who completed the whole vaccination course and had antibody results). Non-inferiority in the phase 2 trial (neutralising antibody titre of participants from this trial aged 3-17 years vs that of participants aged 18-59 years from a separate phase 3 trial) for clinical outcome assessment was based on the geometric mean ratio (GMR) and was considered met if the lower bound of the 95% CI for the GMR was 0·67 or greater. These trials are registered with ClinicalTrials.gov, NCT04961359 (phase 1) and NCT05109598 (phase 2). FINDINGS: Between July 10 and Sept 4, 2021, 75 children and adolescents were randomly assigned to receive ZF2001 (n=60) or placebo (n=15) in the phase 1 trial and were included in safety and immunogenicity analyses. Between Nov 5, 2021, and Feb 14, 2022, 400 participants (130 aged 3-7 years, 210 aged 6-11 years, and 60 aged 12-17 years) were included in the phase 2 trial and were included in the safety analysis; six participants were excluded from the immunogenicity analyses. 25 (42%) of 60 participants in the ZF2001 group and seven (47%) of 15 participants in the placebo group in phase 1, and 179 (45%) of 400 participants in phase 2, had adverse events within 30 days after the third vaccination, without a significant difference between groups in phase 1. Most adverse events were grade 1 or 2 (73 [97%] of 75 in the phase 1 trial, and 391 [98%] of 400 in the phase 2 trial). One participant in the phase 1 trial and three in the phase 2 trial who received ZF2001 had serious adverse events. One serious adverse event (acute allergic dermatitis) in the phase 2 trial was possibly related to the vaccine. In the phase 1 trial, on day 30 after the third dose, in the ZF2001 group, seroconversion of neutralising antibodies against SARS-CoV-2 was observed in 56 (93%; 95% CI 84-98) of 60 participants, with a GMT of 176·5 (95% CI 118·6-262·8), and seroconversion of RBD-binding antibodies was observed in all 60 (100%; 95% CI 94-100) participants, with a GMC of 47·7 IU/mL (95% CI 40·1-56·6). In the phase 2 trial, on day 14 after the third dose, seroconversion of neutralising antibodies against SARS-CoV-2 was seen in 392 (99%; 95% CI 98-100) participants, with a GMT of 245·4 (95% CI 220·0-273·7), and seroconversion of RBD-binding antibodies was observed in all 394 (100%; 99-100) participants, with a GMT of 8021 (7366-8734). On day 14 after the third dose, seroconversion of neutralising antibodies against the omicron subvariant BA.2 was observed in 375 (95%; 95% CI 93-97) of 394 participants, with a GMT of 42·9 (95% CI 37·9-48·5). For the non-inferiority comparison of participants aged 3-17 years with those aged 18-59 years for SARS-CoV-2 neutralising antibodies, the adjusted GMR was 8·6 (95% CI 7·0-10·4), with the lower bound of the GMR greater than 0·67. INTERPRETATION: ZF2001 is safe, well tolerated, and immunogenic in children and adolescents aged 3-17 years. Vaccine-elicited sera can neutralise the omicron BA.2 subvariant, but with reduced activity. The results support further studies of ZF2001 in children and adolescents. FUNDING: Anhui Zhifei Longcom Biopharmaceutical and the Excellent Young Scientist Program from National Natural Science Foundation of China. TRANSLATION: For the Chinese translation of the abstract see Supplementary Materials section.

Safety and immunogenicity following a homologous booster dose of CoronaVac in children and adolescents.

Data on safety and immunity elicited by a third booster dose of inactivated COVID-19 vaccine in children and adolescents are scarce. Here we conducted a study based on a double-blind, randomised, placebo-controlled phase 2 clinical trial (NCT04551547) to assess the safety and immunogenicity of a third dose of CoronaVac. In this study, 384 participants in the vaccine group were assigned to two cohorts. One received the third dose at a 10-months interval (cohort 1) and the other one at a 12-months interval (cohort 2). The primary endpoint is safety and immunogenicity following a third dose of CoronaVac. The secondary endpoint is antibody persistence following the primary two-dose schedule. Severities of local and systemic adverse reactions reported within 28 days after dose 3 were mild and moderate in both cohorts. A third dose of CoronaVac increased GMTs to 681.0 (95%CI: 545.2-850.7) in cohort 1 and 745.2 (95%CI: 577.0-962.3) in cohort 2. Seropositivity rates against the prototype were 100% on day 28 after dose 3. Seropositivity rates against the Omicron variant were 90.6% (cohort 1) and 91.5% (cohort 2). A homologous booster dose of CoronaVac is safe and induces a significant neutralising antibody levels increase in children and adolescents.

Efficacy and Safety of the RBD-Dimer-Based Covid-19 Vaccine ZF2001 in Adults.

BACKGROUND: The ZF2001 vaccine, which contains a dimeric form of the receptor-binding domain of severe acute respiratory syndrome coronavirus 2 and aluminum hydroxide as an adjuvant, was shown to be safe, with an acceptable side-effect profile, and immunogenic in adults in phase 1 and 2 clinical trials. METHODS: We conducted a randomized, double-blind, placebo-controlled, phase 3 trial to investigate the efficacy and confirm the safety of ZF2001. The trial was performed at 31 clinical centers across Uzbekistan, Indonesia, Pakistan, and Ecuador; an additional center in China was included in the safety analysis only. Adult participants (≥18 years of age) were randomly assigned in a 1:1 ratio to receive a total of three 25-µg doses (30 days apart) of ZF2001 or placebo. The primary end point was the occurrence of symptomatic coronavirus disease 2019 (Covid-19), as confirmed on polymerase-chain-reaction assay, at least 7 days after receipt of the third dose. A key secondary efficacy end point was the occurrence of severe-to-critical Covid-19 (including Covid-19-related death) at least 7 days after receipt of the third dose. RESULTS: Between December 12, 2020, and December 15, 2021, a total of 28,873 participants received at least one dose of ZF2001 or placebo and were included in the safety analysis; 25,193 participants who had completed the three-dose regimen, for whom there were approximately 6 months of follow-up data, were included in the updated primary efficacy analysis that was conducted at the second data cutoff date of December 15, 2021. In the updated analysis, primary end-point cases were reported in 158 of 12,625 participants in the ZF2001 group and in 580 of 12,568 participants in the placebo group, for a vaccine efficacy of 75.7% (95% confidence interval [CI], 71.0 to 79.8). Severe-to-critical Covid-19 occurred in 6 participants in the ZF2001 group and in 43 in the placebo group, for a vaccine efficacy of 87.6% (95% CI, 70.6 to 95.7); Covid-19-related death occurred in 2 and 12 participants, respectively, for a vaccine efficacy of 86.5% (95% CI, 38.9 to 98.5). The incidence of adverse events and serious adverse events was balanced in the two groups, and there were no vaccine-related deaths. Most adverse reactions (98.5%) were of grade 1 or 2. CONCLUSIONS: In a large cohort of adults, the ZF2001 vaccine was shown to be safe and effective against symptomatic and severe-to-critical Covid-19 for at least 6 months after full vaccination. (Funded by the National Science and Technology Major Project and others; ClinicalTrials.gov number, NCT04646590.).

Safety, Immunogenicity and Lot-to-Lot Consistency of Sabin-Strain Inactivated Poliovirus Vaccine in 2-Month-Old Infants: A Double-Blind, Randomized Phase III Trial.

BACKGROUND: The Sabin-strain-based inactivated poliovirus vaccine (sIPV) plays an important role in poliomyelitis eradication in developing countries. As part of the phase III clinical development program, this study aimed to evaluate the safety, immunogenicity and lot-to-lot consistency of the sIPV in 2-month-old infants. METHOD: We conducted a phase III, randomized, double-blind, positive-controlled trial in which 1300 healthy infants were randomly assigned to four groups in a 1:1:1:1 ratio to receive one of the three lots of the sIPV or the control IPV at 2, 3 and 4 months of age. Serum samples were collected before the first dose and 30 days after the third dose of vaccination to assess the immunogenicity. Solicited local and systemic reactions were recorded within 7 days and unsolicited adverse events within 30 days after each vaccination. RESULTS: Of the 1300 randomized infants, 1190 infants completed the study and were included in the per-protocol population. The seroconversion rates in the three lots of the sIPV were 95.67%, 97.03% and 95.59%, respectively, for type 1; 94.33%, 93.73% and 92.88%, respectively, for type 2; and 98.67%, 99.67% and 99.32%, respectively, for type 3. The ratios of GMTs for poliovirus types 1, 2 and 3 of each pair of lots were all between 0.67 and 1.50, therefore meeting the predefined immunological equivalence criteria. For the seroconversion rate of poliovirus types 1, 2 and 3, the pooled sIPV group was non-inferior to the IPV group. The incidence of solicited and unsolicited adverse reactions (ARs) was similar in the pooled sIPV lots and the IPV group, and most of them were mild to moderate in severity. Non-vaccine-related serious adverse events (SAEs) were reported. CONCLUSIONS: Three consecutive lots of sIPV demonstrated robust and consistent immunogenicity. The safety and tolerability of the sIPV was acceptable and similar to that of the IPV.

The impact of different IPV-OPV sequential immunization programs on hepatitis A and hepatitis B vaccine efficacy.

In recent years, the Global Polio Eradication Initiative has gradually implemented a global shift in polio immunization programs. Few studies cover polio immunization program impacts on the efficacy of other vaccines. This study investigated whether polio immunization programs affected hepatitis A (HepA) and hepatitis B (HepB) vaccination efficacy. Serum samples were collected from 968 infants before the first dose of polio vaccine, 28 days after completing primary polio immunization, and at 24 months old. Infants were classified into six polio immunization program groups: 1sIPV+2bOPV, 2sIPV+1bOPV, 2sIPV+1tOPV, 1cIPV+2bOPV, 2cIPV+1bOPV, and 2cIPV+1tOPV (sIPV: Sabin inactivated poliovirus vaccine; cIPV: Salk inactivated poliovirus vaccine; b, bivalent; t, trivalent; OPV, oral polio vaccine). No significant differences existed in antibody titers against HepA virus (anti-HAV) among the polio immunization program groups at any of the three time points (pre-first dose [p = 0.412], 28 days after primary immunization [p = 0.676], 24 months old [p = 0.556]). Before the first dose (p = 0.178) and at age 24 months (p = 0.987), no significant differences existed in HepB surface antibody (HBsAb) titers between the six polio immunization program groups). Twenty-eight days after primary immunization, no significant difference existed in HBsAb titers between groups after Bonferroni correction. Following HepA and HepB immunization, anti-HAV and HBsAb positivity reached > 98% in all groups, reflecting effective immunization. Our data suggest that different polio immunization programs did not affect HepA and HepB vaccine efficacy; HepA and HepB vaccines maintained high effectiveness irrespective of polio immunization program. This trial was registered on Clinical Trials.gov: NCT03614702.

Immunogenicity of fractional-dose of inactivated poliomyelitis vaccine made from Sabin strains delivered by intradermal vaccination in Wistar rats.

Reducing the amount of antigen is an important strategy to resolve the present shortage of IPV supply for global polio eradication. In the study, we compared the immunogenicity of adjuvanted and non-adjuvanted fractional-dose of IPV made from Sabin strains (sIPV) by intradermal (ID) administration versus the full-dose of sIPV by intramuscular (IM) administration in rats by comparing seroconversion rates and geometric mean titers (GMTs) of neutralizing antibodies (NAbs). We found that, after the full 0, 1, 2 months schedule immunizations, the seroconversion rates in all groups reached 100% except non-adjuvanted 1/6 dose group. After 2 immunizations, the seroconversion rates in all the adjuvanted fractional-dose groups and the full-dose group reached 100%. The GMTs of NAbs induced by adjuvanted 1/12 fractional-dose and full-dose of sIPV were similar and dynamics of the antibody responses were consistent. We proves that the Th1/Th2 balance was not changed by the administration route by comparing ratios of the IgG subclass. Our study confirms that ID administration could reduce the required amount of antigens, the adjuvanted fractional-dose resulted in earlier and higher antibody response for all serotypes than that of non-adjuvanted fractional-dose, and the NAbs responses elicited by 1/12 dose was comparable to that by full-dose of sIPV.

Immunogenicity of two-dose and three-dose vaccination schedules with Sabin inactivated poliovirus vaccine in China: An open-label, randomized, controlled trial.

BACKGROUND: We assessed immunogenicity of three-dose and two-dose immunization schedules with a Sabin-strain inactivated poliovirus vaccine (sIPV) produced by one Chinese vaccine manufacturer. METHODS: This was an open label, randomized, controlled trial conducted in 16 vaccination clinics in Shandong province. Infants were allocated randomly to either a 3-dose study arm (sIPV administered at 2, 3, and 4 months of age) or a 2-dose arm (sIPV administered at 4 and 8-11 months of age). Poliovirus neutralizing antibodies were measured in sera collected prior to the first sIPV dose and one month after the last dose. FINDINGS: We enrolled 560 infants; 536 (95.7%) completed the study. Final seropositivity rates were >98% for all three serotypes in both study arms. There were no statistically significant differences in seropositivity between the 2-dose and the 3-dose schedule. Final median reciprocal titres of polio antibodies were high overall (>1:768 for all serotypes) and statistically significantly higher in 2-dose recipients compared with 3-dose recipients (p < 0.001). INTERPRETATION: This study offers evidence that two doses of sIPV administered at 4 and 8-11 months of age and three doses of sIPV administered at 2, 3, and 4 months of age both provide serological protection against poliomyelitis. Median reciprocal titres of polio antibodies were high overall, and were more related to the interval between doses than the number of doses, with the longer interval of the 2-dose schedule producing higher reciprocal titres than the shorter-interval 3-dose schedule. The protection provided by the 3-dose schedule is achieved earlier in life than the protection with the 2-dose schedule. Countries planning to use an IPV-only schedule in the post-eradication era can consider this 2-dose sIPV option as an immunogenic and dose-sparing strategy. FUNDING: World Health Organization (from a grant from International PolioPlus Committee, Rotary International, Evanston, IL, USA).

Post hoc analysis of two clinical trials to compare the immunogenicity and safety of different polio immunization schedules in Chinese infants.

BACKGROUND: A comparative analysis of the immunogenicity and safety of different poliovirus immunization schedules in Chinese infants is imperative to guide the administration of efficient strategies for the eradication of poliomyelitis. METHODS: A post hoc analysis was conducted with the data from two poliovirus vaccine clinical trials involving a combined total of 2,400 infants aged 60-90 days. Trivalent oral poliovirus vaccine (tOPV), bivalent oral poliovirus vaccine (bOPV), Sabin strain-based inactivated poliovirus vaccine (sIPV), and conventional inactivated poliovirus vaccine (cIPV) were used in different schedules, the immunogenicity and safety of which were compared 28 days after the last of three doses. RESULTS: In a per-protocol set analysis, the tOPV-tOPV-tOPV schedule induced seroconversion in 99.1%, 98.2%, and 96.0% of the inoculated infants for poliovirus type I, II, and III, respectively. The seroconversions for poliovirus types I and III were each almost 100% after immunization with the cIPV-bOPV-bOPV, sIPV-sIPV-bOPV, cIPV-cIPV-bOPV, sIPV-sIPV-tOPV, cIPV-cIPV-tOPV, or sIPV-bOPV-bOPV schedule. However, the schedules that used one IPV dose followed by two (poliovirus type I and III) bOPV doses failed to induce high-level immunity against type II poliovirus. IPV-related schedules were associated with a slightly higher incidence of adverse events (AEs). CONCLUSIONS: If the capacity of IPV can be increased, two or more doses of IPV should be administered before vaccination with bOPV in a sequential schedule to improve immunity against type II poliovirus.

Immunogenicity and safety of the inactivated poliomyelitis vaccine made from Sabin strains in a phase IV clinical trial for the vaccination of a large population.

As a recently launched novel vaccine used as one of the vaccines for the final eradication of polios worldwide, complete data on the consistency and immunogenicity characteristics of the inactivated poliomyelitis vaccine made from the Sabin strain (sIPV) and its safety in large-scale populations are required to support the future use of this vaccine worldwide. A phase IV clinical trial was conducted to perform an immunogenicity evaluation of lot-to-lot consistency of three commercial batches of sIPV in 1200 infants and to investigate the vaccine's safety on a large-scale in 20,019 infants for active monitoring and 29,683 infants for passive monitoring through the Adverse Event Following Immunization (AEFI) reporting system in China. In the immunogenicity evaluation, the average seroconversion rates for type I, type II and type III of the three groups were 99.83%, 98.93% and 99.44%, respectively. No differences in the seroconversion rate and the GMT ratios were noted in the pair-to-pair comparisons. In the large-scale safety evaluation, most adverse reactions occurred 0-30 days after the first doses, and the common local and systemic reactions were similar to those in the phase III clinical trial, with low incidence in both activated and passive monitoring. In conclusion, sIPV exhibits good lot-to-lot consistency and safety in large-scale populations; thus, it is qualified to serve as one of the vaccines for use in eradicating all wild and vaccine-derived polioviruses worldwide in the near future. Clinic Trial Registration. NCT04224519 and NCT04220515.

Safety and Immunogenicity of Sabin Strain Inactivated Poliovirus Vaccine Compared With Salk Strain Inactivated Poliovirus Vaccine, in Different Sequential Schedules With Bivalent Oral Poliovirus Vaccine: Randomized Controlled Noninferiority Clinical Trials in China.

BACKGROUND: A new Sabin strain inactivated poliovirus vaccine (sIPV) proved to be immunogenic and safe in all IPV primary immunization in the previous study, with the corresponding profiles in sequential immunizations unclear. METHODS: Two clinical trials on the "IPV + 2 bivalent oral polio vaccine (2bOPV)" (Trial A) and "2IPV + bOPV" (Trial B) vaccination were conducted. Both clinical trials were randomized, controlled, double-blinded, noninferiority trials, and wild-strain IPV (wIPV) was adopted as the control vaccine. In each clinical trial, 240 healthy infants were enrolled and randomly assigned to receive sequential vaccinations containing sIPV or wIPV. Immunogenicity and safety were assessed using per-protocol and safety populations, respectively. RESULTS: For Trial A, the seroconversion rates in the experimental and control groups were 100% and 99.1%, respectively, against type 1; both 100.0% against type 3. For Trial B, the seroconversion rates in experimental and control groups were 99.2% and 100.0%, respectively, against type 1; both 100% against type 3. No serious adverse events related to vaccines were reported. CONCLUSIONS: The new sIPV demonstrated an immunogenicity noninferior to that of the wIPV and a good safety profile in sequential vaccination with bOPV. CLINICAL TRIAL NUMBERS: NCT:03822754; NCT:03822767.

Immunogenicity and Safety of a Sabin Strain-Based Inactivated Polio Vaccine: A Phase 3 Clinical Trial.

BACKGROUND: The Sabin strain-based inactivated polio vaccine (sIPV) plays a vital role in eradicating poliomyelitis in developing countries. METHODS: The study was designed as a randomized, controlled, double-blinded, noninferiority trial. A total of 1200 healthy infants aged 60-90 days were enrolled and randomly assigned to receive 3 doses of either sIPV (the experimental arm) or IPV (the control arm) at days 0, 30, and 60. Immunogenicity and safety outcomes were assessed using the per-protocol and safety populations, respectively. RESULTS: A total of 553 and 562 participants in the sIPV and IPV groups, respectively, were included in the per-protocol population. Seroconversion rates in the sIPV and IPV groups were 98.0% and 94.1%, respectively, for type 1 poliovirus (P < .01); 94.8% and 84.0%, respectively, for type 2 (P < .01); and 98.9% and 97.7%, respectively, for type 3 (P = .11). A total of 599 and 600 participants in the sIPV and IPV groups, respectively, were included in the safety population. Fever was the most common adverse event, occurring in 61.6% and 49.8% of participants in the experimental and control arms, respectively (P < .01). CONCLUSIONS: The sIPV demonstrated an immunogenicity profile noninferior to that of the conventional IPV and had a good safety profile. CLINICAL TRIALS REGISTRATION: NCT03526978.

A simple and safe antibody neutralization assay based on polio pseudoviruses.

The evaluation of the immunogenicity of Sabin strain based Inactivated Poliovirus Vaccines (sIPV) necessitates the use of wild strains in neutralization assays to assess the potential cross-reactivity of antibodies. The live virus strains including wild and Sabin strains must be handled in level 3 biocontainment laboratories. To develop an alternative assay without the use of a live virus, we constructed Mahoney, MEF-1, and Saukett pseudovirions by inserting luciferase reporter genes into intact capsid proteins. Afterward, we developed a pseudovirus-based neutralization test (pNT) and evaluated for the specificity and reproducibility. We tested serum samples from a clinical trial on sIPV vaccines by pNT and compared the results with those obtained from conventional neutralization tests (cNT). A strong correlation was observed between two methods, with the correlation coefficients of all three types of IPV vaccines being greater than 0.82 (p < 0.0001). The Geometric Mean Titer (GMT) values obtained by pNT were approximately four times higher than that by cNT, revealing the better sensitivity of pNT. In conclusion, pNT is a safe, rapid and sensitive quantitative assay with the potential of being an alternative for the evaluation of the potency of polio vaccines.

Safety and immunogenicity of inactivated poliovirus vaccine made from Sabin strains: A phase II, randomized, dose-finding trial.

BACKGROUND: In order to completely eradicate polio caused by wild poliovirus infection as well as vaccine-associated paralytic polio (VAPP), Sabin inactivated poliovirus vaccine (sIPV) should be developed to meet the requirements for biosafety and affordable strategy in the developing countries. METHOD: A randomized, double-blinded clinical trial was conducted to compare the immunogenicity and safety among infants aged 2 months (60-90 days) receiving five different vaccination regimens: the test groups (A, B, and C) received three doses of sIPV with high, medium, and low D antigen content, respectively, on the month 0, 1, 2 schedule; two control groups (D and E) received three doses of conventional IPV (cIPV) or sIPV (CAMS), respectively, on the same schedule as that of test groups. Serum samples were collected immediately before the 1st dose and 30 days after the 3rd dose vaccination to assess the immunogenicity. Adverse events occurring within 30 days after each dose were collected to assess the safety. RESULTS: After three doses, seroconversion rates in groups A-E were 100%, 98.2%, 100%, 100%, and 100%, respectively, for type 1; 99.1%, 100%, 98.1%, 100%, and 97.1%, respectively, for type 2; and 100%, 100%, 100%, 100%, and 99.0%, respectively, for type 3. The seropositive rates (≥1:8) of groups A-E for all types were nearly 100%. The GMTs in the target dose group (group B) were 4635, 342, and 2218 for type 1-3, respectively. The most common injection-site and systemic adverse reactions were swelling and fever respectively. The swelling (4.2%, P = 0.0075) and fever (58.3%, P = 0.0188) frequency of group A were statistically significantly higher than any other groups. CONCLUSION: The test sIPV generally demonstrated good safety and immunogenicity. The medium-D antigen dose would be a preferred choice for the further phase III clinical trial in consideration of its high immunogenicity for all serotypes and the satisfying tolerance. CLINICAL TRIALS REGISTRATION: NCT02985320.

Immune Serum From Sabin Inactivated Poliovirus Vaccine Immunization Neutralizes Multiple Individual Wild and Vaccine-Derived Polioviruses.

BACKGROUND: A Sabin strain-based inactivated poliomyelitis vaccine (Sabin-IPV) is the rational option for completely eradicating poliovirus transmission. The neutralizing capacity of Sabin-IPV immune serum to different strains of poliovirus is a key indicator of the clinical protective efficacy of this vaccine. METHODS: Sera collected from 500 infants enrolled in a randomized, blinded, positive control, phase 2 clinical trial were randomly divided into 5 groups: Groups A, B, and C received high, medium, and low doses, respectively, of Sabin-IPV, while groups D and E received trivalent oral polio vaccine and Salk strain-based IPV, respectively, all on the same schedule. Immune sera were collected after the third dose of primary immunization, and tested in cross-neutralization assays against 19 poliovirus strains of all 3 types. RESULTS: All immune sera from all 5 groups interacted with the 19 poliovirus strains with various titers and in a dose-dependent manner. One type 2 immunodeficiency-associated vaccine-derived poliovirus strain was not recognized by these immune sera. CONCLUSIONS: Sabin-IPV vaccine can induce protective antibodies against currently circulating and reference wild poliovirus strains and most vaccine-derived poliovirus strains, with rare exceptions. CLINICAL TRIALS REGISTRATION: NCT01056705.