Immune imprinting, breadth of variant recognition, and germinal center response in human SARS-CoV-2 infection and vaccination.

During the SARS-CoV-2 pandemic, novel and traditional vaccine strategies have been deployed globally. We investigated whether antibodies stimulated by mRNA vaccination (BNT162b2), including third-dose boosting, differ from those generated by infection or adenoviral (ChAdOx1-S and Gam-COVID-Vac) or inactivated viral (BBIBP-CorV) vaccines. We analyzed human lymph nodes after infection or mRNA vaccination for correlates of serological differences. Antibody breadth against viral variants is lower after infection compared with all vaccines evaluated but improves over several months. Viral variant infection elicits variant-specific antibodies, but prior mRNA vaccination imprints serological responses toward Wuhan-Hu-1 rather than variant antigens. In contrast to disrupted germinal centers (GCs) in lymph nodes during infection, mRNA vaccination stimulates robust GCs containing vaccine mRNA and spike antigen up to 8 weeks postvaccination in some cases. SARS-CoV-2 antibody specificity, breadth, and maturation are affected by imprinting from exposure history and distinct histological and antigenic contexts in infection compared with vaccination.

Development of an Inactivated Vaccine Candidate, BBIBP-CorV, with Potent Protection against SARS-CoV-2.

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) threatens global public health. The development of a vaccine is urgently needed for the prevention and control of COVID-19. Here, we report the pilot-scale production of an inactivated SARS-CoV-2 vaccine candidate (BBIBP-CorV) that induces high levels of neutralizing antibodies titers in mice, rats, guinea pigs, rabbits, and nonhuman primates (cynomolgus monkeys and rhesus macaques) to provide protection against SARS-CoV-2. Two-dose immunizations using 2 µg/dose of BBIBP-CorV provided highly efficient protection against SARS-CoV-2 intratracheal challenge in rhesus macaques, without detectable antibody-dependent enhancement of infection. In addition, BBIBP-CorV exhibits efficient productivity and good genetic stability for vaccine manufacture. These results support the further evaluation of BBIBP-CorV in a clinical trial.

Comparing the immunogenicity of COVID-19 infection and vaccination in pregnant women as measured by anti-S IgG.

BACKGROUND: Pregnancy is a critical time for women, making them more susceptible to infectious diseases like COVID-19. This study aims to determine the immunogenicity of COVID-19 in pregnant women who have been infected compared to those who have received the inactive COVID-19 vaccine. MATERIALS AND METHODS: In this retrospective cohort study, pregnant women who received the inactivated COVID-19 vaccine (Sinopharm) and those with a history of COVID-19 infection during pregnancy were studied. Participants who had experienced stillbirth, received different COVID-19 vaccines, or had intrauterine fetal death were excluded from the study. Overall, the study included 140 participants. The participants were divided into two groups of 70 participants - pregnant women who received the Sinopharm vaccine and pregnant women who had COVID-19 infection during pregnancy. Before delivery, blood samples were collected from all mothers to evaluate the maternal immunoglobulin G (IgG) level. Blood samples were also taken from the baby's umbilical cord during delivery to measure the newborn's IgG level. Additionally, blood samples were collected from babies whose mothers showed signs of acute infection to measure their IgM levels and evaluate vertical transmission. FINDINGS: The study found a significant relationship between the mean level of maternal IgG and umbilical cord IgG within the groups (P < 0.001). The highest levels of maternal IgG (2.50 ± 2.17) and umbilical cord IgG (2.43 ± 2.09) were observed in pregnant women with a previous COVID-19 infection and no history of vaccination (P < 0.001). Only one baby was born with a positive IgM, and this baby was born to a mother who showed signs of COVID-19 infection in the last five days of pregnancy. The mother was 28 years old, with a BMI of 33; it was her first pregnancy, and she gave birth to a male newborn at term. CONCLUSION: Administering an inactivated vaccine during pregnancy can generate immunity in both the mother and the child. However, the vaccine's immunity level may not be as potent as that conferred by COVID-19 infection during pregnancy. Nonetheless, the risk of vertical transmission of COVID-19 is considered minimal and can be classified as negligible.

Evaluating long-term antibody responses to booster doses of COVID-19 vaccines in the Pakistani population.

Background & Objective: Nearly 80 million of the Pakistani population received two doses of the BBIBP-CorV vaccine, against SARS-CoV-2, and 2.6 million people received heterologous booster doses up to February 2022. Our objective was to measure the long-term change of antibody titers in persons vaccinated with Pfizer-BioNTech COVID-19 following two doses of BBIBP-CorV. Methods: Serum specimens from forty-three participants were collected 4-8 weeks following two doses of BBIBP-CorV at the Indus Hospital & Health Network, Karachi. A second set of serum specimens were collected 2-12 months after Pfizer-BioNTech COVID-19 booster dose administration. Chemiluminescent Microparticle Immunoassay (CMIA, Abbott Alinity Quant), and the pseudotyped lentivirus antibody neutralization assay were performed on all specimens. The latter assay was reported as log half-maximal inhibitory concentrations (IC50), calculated using a nonlinear regression algorithm (log [inhibitor] versus normalized response variable slope) in Graph Pad Prism 9. Paired sample t-test was used to ascertain the statistical significance of the difference in means of antibody titers obtained before and after the booster vaccine doses. Results: Mean log10 values obtained with CMIA before and after the booster dose were 2.90 AU/mL and 3.87 AU/mL respectively, while the corresponding log10 IC50 values obtained through pseudotyped lentivirus antibody neutralization assay were 2.45 and 2.80. These differences were statistically significant with CMIA (p = <0.00001), but not with pseudotyped lentivirus antibody neutralization assay (p = 0.06318.). Conclusion: A heterologous booster dose with Pfizer-BioNTech COVID-19 vaccine following two doses of BBIBP results in increased total antibody titers, though neutralizing antibody titers may start to wane a few months after the booster dose.

Immunodominant SARS-CoV-2-specific CD4+ and CD8+ T-cell responses elicited by inactivated vaccines in healthy adults.

Safety profiles and humoral responses to inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines have been previously assessed, but cellular immune responses to inactivated SARS-CoV-2 vaccines remain understudied. Here, we report the comprehensive characteristics of SARS-CoV-2-specific CD4+ and CD8+ T-cell responses elicited by the BBIBP-CorV vaccine. A total of 295 healthy adults were recruited, and SARS-CoV-2-specific T-cell responses were detected after stimulation with overlapping peptide pools spanning the entire length of the envelope (E), membrane (M), nucleocapsid (N), and spike (S) proteins. Robust and durable CD4+ (p < 0.0001) and CD8+ (p < 0.0001) T-cell responses specific to SARS-CoV-2 were detected following the third vaccination, with an increase in specific CD8+ T-cells, compared to CD4+ T-cells. Cytokine profiles showed that interferon gamma and tumor necrosis factor-α were predominantly expressed with the negligible expression of interleukin (IL)-4 and IL-10, indicating a Th1- or Tc1-biased response. Compared to E and M proteins, N and S activated a higher proportion of specific T-cells with broader functions. The predominant frequency of the N antigen (49/89) was highest for CD4+ T-cell immunity. Furthermore, N19-36 and N391-408 were identified to contain dominant CD8+ and CD4+ T-cell epitopes, respectively. In addition, N19-36 -specific CD8+ T-cells were mainly effector memory CD45RA cells, whereas N391-408 -specific CD4+ T-cells were mainly effector memory cells. Therefore, this study reports comprehensive features of T-cell immunity induced by the inactivated SARS-CoV-2 vaccine BBIBP-CorV and proposes highly conserved candidate peptides which may be beneficial in vaccine optimization.

CoronaVac and BBIBP-CorV vaccines against SARS-CoV-2 during predominant circulation of Omicron BA.5.2 and BF.7 in China, a retrospective cohort study.

Pandemic of COVID-19 hit China at the end of 2022. According to China Center for Disease Control and Prevention, Omicron BA.5.2 and BF.7 were the main circulating variants. Chinese people had a high COVID-19 vaccination rate, and the most widely used vaccines were CoronaVac (Sinovac) and BBIBP-CorV (Sinopharm). An online questionnaire was distributed to survey the vaccination history and infection information of China mainland residents during this pandemic. A total of 4250 subjects were included for propensity score matching, 566 unvaccinated subjects and 1072 vaccinated subjects were finally included to analyze the effects of the two vaccines on BA.5.2 and BF.7. The SARS-CoV-2 infection rate was 84.5% in the vaccinated group and 82.3% in the unvaccinated group (p = 0.255). Vaccinated subjects had significantly higher rates of COVID-19-related symptoms, including fever, cough, nasal obstruction, runny nose, and sore throat. However, vaccinated people had lower risk of pneumonia (odds ratio [OR]: 0.467, 95% confidence interval [CI]: 0.286-0.762) and hospitalization (OR: 0.290, 95% CI: 0.097-0.870) due to COVID-19. In general, the current study did not observe the protective effect of CoronaVac and BBIBP CorV against BA.5.2 and BF.7 infection. However, these vaccines can still reduce the risk of adverse outcomes such as pneumonia and hospitalization.

Safety and efficacy of the FAKHRAVAC compared with BBIBP-Corv2 against SARS-CoV-2 in adults: a non-inferiority multi-center trial.

BACKGROUND: We compared Fakhravac and BBIBP-Corv2 vaccines in a phase III trial. METHOD: We conducted a multicenter, parallel-group, active-control, non-inferiority clinical trial with pragmatic considerations assessing the safety and efficacy of Fakhravac and BBIBP-Corv2 vaccines. We started with two randomized double-blind arms and added two non-randomized open-label arms (based on participant preference) because of slow recruitment. The adult population received 0.5 ml (10 µg per dose) intramuscular injections of Fakhravac or BBIBP-Corv-2 vaccines 21 days apart. The primary outcome was the occurrence of PCR-positive symptomatic Covid-19 disease 14 days or more after the second injection. A 10% non-inferiority margin to the reported 72.8% efficacy of BBIBP-Corv2 was assumed. Cox proportional hazard modeling was used to estimate hazard ratios and their 95% confidence intervals. RESULT: We enrolled 24,056 adults in four groups (randomized-Fakhravac: 824, randomized-BBIBP-Corv2: 832; Non-randomized-Fakhravac: 19,429, Non-randomized-BBIBP-Corv2: 2971). All observed local and systemic adverse reactions were generally self-limited and resolved completely. We observed similar Serious Adverse Event (SAE) rates in the BBIBP-Corv2 (2.57, 95% CI 1.33-4.49) and Fakhravac (2.25, 95% CI 1.72-2.89) groups; none of which were related to the vaccines received. We recorded 9815 Medically Attendant Adverse Events (MAAE), 736 of which were categorized as somehow related. The rate of related MAAE in the Fakhravac was similar to the BBIBP-Corv2 groups (0.31 and 0.26 per 1000 person-day) in the randomized and considerably higher (0.24 and 0.07 per 1000 person-day) in the non-randomized arms. We observed 129 (35% of the 365 required by target sample size) events of PCR + symptomatic Covid-19 during four months of active follow-up in the randomized arm, demonstrating that those receiving the Fakhravac vaccine were significantly less likely (HR = 0.69; 95% CI 0.49-0.98) to be diagnosed with PCR + symptomatic Covid-19 compared with those receiving BBIBP-Corv2 vaccine. After adjusting for type I error using the O'Brien Fleming method, the Fakhravac vaccine was non-inferior to the BBIBP-Corv2 (assuming a 10% non-inferiority margin to the reported 72.8% BBIBP-Corv2 vaccine efficacy; HR < 1.35) (One-way test: HR = 0.66; 99.8% CI 0.38-1.15). In the non-randomized arm, the results were inconclusive (HR = 1.23; 95% CI 0.96-1.61). We observed 5 cases of hospitalized Covid-19 in the randomized arm, none of which occurred in the Fakhravac vaccine group. Those receiving the Fakhravac vaccine were four times less likely to go to the hospital because of a Covid-19 diagnosis (HR = 0.24; 95% CI 0.10-0.60). The vaccine efficacy of the Fakhravac vaccine is estimated to be 81.5% (95% CI 81-82.4%). CONCLUSION: Fakhravac inactivated SARS-CoV-2 vaccine has comparable safety and efficacy to the BBIBP-Corv2 vaccine. Trial registration This study was registered with the Iranian Registry of Clinical Trials ( www.irct.ir : IRCT20210206050259N3).

RBD-specific antibody responses after two doses of BBIBP-CorV (Sinopharm, Beijing CNBG) vaccine.

BACKGROUND: Limited information is available on the effectiveness of the BBIBP-CorV (Sinopharm, Beijing CNBG) vaccine, especially in the elderly, despite the fact that it is approved in more than 50 countries. METHODS: RBD-specific antibody titres, as a rapidly available and highly predictive surrogate marker, were measured after two doses of the BBIBP-CorV vaccine in 450 subjects. Results were analyzed in a multivariable model accounting for age, sex and time since the administration of the second dose of the vaccine. RESULTS: Sex and time since the second dose had little association with the antibody titres. Age, however, was highly relevant: measurable antibody levels were present in about 90% of individuals below the age of 50, but antibody production after BBIBP-CorV vaccination was strongly reduced with increasing age. A large number of elderly subjects, reaching 25% at 60 years, and up to 50% at ages over 80, were found not to produce any protective antibody. CONCLUSIONS: RBD-specific antibody titre, as a correlate of protection for COVID-19 disease susceptibility, should help to evaluate the effectiveness of the BBIBP-CorV vaccine. Results suggest that proper measures should be undertaken to prevent a potential outbreak of COVID-19 in BBIBP-CorV vaccinated but eventually unprotected elderly individuals.

Humoral immunity of BBIBP-CorV (Sinopharm) in kidney transplant recipients: Is it time to revise vaccination strategies.

BACKGROUND: The mortality of coronavirus disease 2019 (COVID-19) is high in transplant patients, and effective vaccination is aimed to reduce severe disease and mortality. METHODS: We conducted a cross-sectional study to evaluate humoral and cellular response to two 4-µg doses of BBIBP-CorV vaccine in 100 kidney transplant recipients, using anti-spike IgG, total anti-receptor-binding domain, neutralizing antibody (Ab) level (enzyme-linked immunoassay), and interferon-gamma release assay (IGRA). RESULTS: Seroconversion was evaluated 85.84 ± 30.72 days after the second dose. Note that, 58% of all and 43.05% of infection-naïve participants have developed at least one of the tested antibodies. IGRA was positive in 30.7% of tested transplant recipients. Sixty percent of the participants had either humoral or cellular responses to COVID-19. Only age was independently linked to seropositivity of any degree after vaccination (p < .05). COVID-naïve patients older than 60 years developed significantly less neutralizing Abs. (p = .011). Six patients developed mild COVID infection more than a month after the second dose of the vaccine (54.5 ± 20.8 days). No vaccine-related adverse effects were reported, except self-limited mild to moderate fever and injection site pain. CONCLUSION: BBIBP-CorV vaccine can be used safely in kidney transplant recipients, although impaired cellular and humoral immunity necessitate adjustments in vaccination strategies, like higher (8-µg doses), fourth booster dose, or boost with different platform vaccine.

Extensive cutaneous leukocytoclastic vasculitis after Sinopharm vaccine: Case report and review of the literature.

Cutaneous leukocytoclastic vasculitis (LCV) has been reported as a rare form of cutaneous reaction to different SARS-Cov-2 vaccines. Herein, we present the first case of cutaneous LCV following BBIBP-CorV (Sinopharm) vaccine that occurred in a female patient with no prior comorbidities. A literature review about similar cases following different COVID-19 vaccines is discussed.

Real-world study of the effectiveness of BBIBP-CorV (Sinopharm) COVID-19 vaccine in the Kingdom of Morocco.

BACKGROUND: The Kingdom of Morocco approved BBIBP-CorV (Sinopharm) COVID-19 vaccine for emergency use on 22 January 2021 in a two-dose, three-to-four-week interval schedule. We conducted a retrospective cohort study to determine real-world BBIBP-CorV vaccine effectiveness (VE) against serious or critical hospitalization of individuals RT-PCR-positive for SARS-CoV-2 during the first five months of BBIBP-CorV use in Morocco. METHODS: The study was conducted among adults 18-99 years old who were tested by RT-PCR for SARS-CoV-2 infection between 1 February and 30 June 2021. RT-PCR results were individually linked with outcomes from the COVID-19 severe or critical hospitalization dataset and with vaccination histories from the national vaccination registration system. Individuals with partial vaccination (< 2 weeks after dose two) or in receipt of any other COVID-19 vaccine were excluded. Unadjusted and adjusted VE estimates against hospitalization for serious or critical illness were made by comparing two-dose vaccinated and unvaccinated individuals in logistic regression models, calculated as (1-odds ratio) * 100%. RESULTS: There were 348,190 individuals able to be matched across the three databases. Among these, 140,892 were fully vaccinated, 206,149 were unvaccinated, and 1,149 received homologous BBIBP-CorV booster doses. Unadjusted, full-series, unboosted BBIBP-CorV VE against hospitalization for serious or critical illness was 90.2% (95%CI: 87.8-92.0%). Full-series, unboosted VE, adjusted for age, sex, and calendar day of RT-PCR test, was 88.5% (95%CI: 85.8-90.7%). Calendar day- and sex-adjusted VE was 96.4% (95%CI: 94.6-97.6%) for individuals < 60 years, and was 53.3% (95%CI: 39.6-63.9%) for individuals 60 years and older. There were no serious or critical illnesses among BBIBP-CorV-boosted individuals. CONCLUSIONS: Effectiveness of Sinopharm's BBIBP-CorV was consistent with phase III clinical trial results. Two doses of BBIBP-CorV was highly protective against COVID-19-associated serious or critical hospitalization in working-age adults under real-world conditions and moderately effective in older adults. Booster dose vaccination was associated with complete protection, regardless of age, although only a small proportion of subjects received booster doses.

Safety and immunogenicity of the NVX-CoV2373 vaccine as a booster in adults previously vaccinated with the BBIBP-CorV vaccine.

This phase 3 observer-blind, randomized, controlled study was conducted in adults ≥18 years of age to assess the safety and immunogenicity of NVX-CoV2373 as a heterologous booster compared to BBIBP-CorV when utilized as a homologous booster. Approximately 1000 participants were randomly assigned in a 1:1 ratio to receive a single dose of NVX-CoV2373 or BBIBP-CorV after prior vaccination with 2 or 3 doses of BBIBP-CorV. Solicited adverse events (AEs) were collected for 7 days after vaccination. Unsolicited AEs were collected for 28 days following the booster dose and serious adverse and adverse events of special interest (AESI) were collected throughout the study. Anti-spike IgG and neutralizing antibodies against SARS-CoV-2 were measured at baseline, day 14, day 28, and day 180. The study achieved its primary non-inferiority endpoint and also demonstrated statistically higher neutralization responses when NVX-CoV2373 was utilized as a heterologous booster compared with BBIBP-CorV as a homologous booster. Both vaccines had an acceptably low reactogenicity profile, and no new safety concerns were found. Heterologous boosting with NVX-CoV2373 was a highly immunogenic and safe vaccine regimen in those previously vaccinated with BBIBP-CorV.

Immunogenicity Persistence of a Third-Dose Homologous BBIBP-CorV/CoronaVac Boosting Vaccination: A Prospective Open-Label Study.

The inactivated whole-virion severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine has been widely used in a two-dose schedule, but with insufficient data on the immunogenicity of homologous BBIBP-CorV/CoronaVac boosting vaccination and too little follow-up to assess the duration of the immunogenic response. We prospectively evaluated the immunogenicity of a third-dose BBIBP-CorV/CoronaVac boosting vaccination, with neutralizing titers against wild type and Omicron assessed at the baseline (immediately before the booster dose), and days 14, 28, 98, and 174 post the third-booster. Of 182 volunteers screened, 165 were assessed eligible for enrolment. No moderate/severe adverse events were observed during the term of the study. From the baseline to day 174 post the third booster, neutralizing titers against wild type and Omicron peaked by approximately sixfold increase (up to 811.83 and 33.40, respectively) at day 14 and slowly decreased over time. The geometric mean titers against Omicron were lower than against type with a 19.8-39. Sixfold reduction at all time points. The seropositivity against Omicron at the baseline, days 14, 28, 98, and 174 after the booster dose was 12.6%, 50.0%, 37.8%, 38.6%, and 22.8%, respectively. Data presented herein indicated that the BBIBP-CorV/CoronaVac booster significantly enhances the neutralizing potency against wild-type strain but elicited weaker neutralizing activity to Omicron. Our findings suggest that individuals receiving booster inactivated vaccine remain at risk for Omicron infection, which is crucial to inform ongoing and future vaccination strategies to combat coronavirus disease 2019.

A real-world study of BBIBP-CorV vaccine effectiveness in a Sri Lanka rural province.

Objective: Real-world studies assessing the effectiveness of the BBIBP-CorV vaccine in low and middle-income countries are limited. We evaluated the BBIBP-CorV vaccine's effectiveness in reducing COVID-19 symptomatic disease, hospitalisation, severe disease, and mortality during the third wave of the pandemic in Sri Lanka. Methods: We conducted a test-negative case-control study in North Central Province from May 2021 to February 2022. Evidence of vaccination was obtained from the national registry. The PCR-positive patients were cases, while negative individuals were controls. Adjusted vaccine effectiveness (aVE) was computed for fully, partially, and non-vaccinated groups in reducing symptomatic disease, hospitalisation, severe disease, and mortality. Results: Our study involved 3305 cases and 3418 controls. The overall aVE for preventing PCR-positive infection in fully vaccinated was 30·8 % (95 % CI:17·9-41·6). In fully vaccinated over 60 years, the overall aVE was 72·3 % (95 % CI: 49·7-84·8). Full vaccination with BBIBP-CorV is effective in reducing hospitalisation, severe COVID-19 disease, and death, with aVE rates of 70·3 % (95 % CI: 57·9-79·0), 88·9 % (95 % CI: 81·8-93·2), and 92·3 % (95 % CI: 84·8-96·1) respectively. Conclusion: Individuals who have received two doses of the BBIBP-CorV vaccine are protected against hospitalisation, severe COVID-19 disease, and death. Duration of protection against hospitalisation, severe COVID-19, and fatal COVID-19 sustained at least 121 days, with no sign of waning during that time.

SARS-CoV-2 specific antibody response after an mRNA vaccine as the third dose: Homologous versus heterologous boost.

The aim of this study was to evaluate immunogenicity and longevity of the humoral immune response within six months after the homologous (BNT162b2/BNT162b2) or heterologous (BBIBP-CorV/BNT162b2) third dose, and to assess breakthrough infections among vaccinees during the Omicron wave in Serbia. Serum samples were analyzed at four timepoints: five months after the primary series; three weeks, three months, and six months after the boost. IgG antibodies against the receptor-binding domain of the spike protein were detected using enzyme-linked fluorescence assay. Both homologous (n = 55) and heterologous group (n = 36) showed a highly significant increase in antibody concentrations (p < 0.001) three weeks after the boost. A moderate inverse correlation between the age of recipients and the antibody levels at three weeks post-boost was observed in the homologous group (p = 0.02, r = -0.37), while the same correlation was not significant for heterologous group (p = 0.55, r = -0.15). Heterologous group had significantly higher antibody concentrations than homologous group at three weeks (Median 851.4(IQR 766.6-894.1); 784.3(676.9-847.4); p = 0.03) and three months post-boost (766.6(534.8-798.9); 496.8(361.6-664.0); p < 0.001). However, a significant decline in antibody response over time was noted for both strategies. The overall incidence of breakthrough cases was estimated at 36.36% (20/55) for homologous, and 16.67% (6/36) for heterologous group, but none of them required hospitalization. Although observed incidence in the homologous group was more than double when compared to the heterologous group, this difference was not statistically significant, most likely due to the small sample size. In conclusion, waning immunity after inactivated vaccine can be recovered by BNT162b2 heterologous boost regardless of the age of recipients, and both boost strategies induced potent humoral immune response and protection against severe COVID-19 during the Omicron wave. However, as the observed incidence of breakthrough infections was higher in the homologous group, although non-significant, this finding could indicate an advantage of heterologous approach.

BBIBP-CorV vaccine effectiveness against COVID-19 in patients aged 60 years and older during the Delta-dominant period in the Federation of Bosnia and Herzegovina, a test-negative case-control study.

COVID-19 vaccine uptake in the Federation of Bosnia and Herzegovina (FBiH) accelerated in the second half of 2021, with greater vaccine availability. In this study, we estimated the vaccine effectiveness (VE) of complete primary series BBIBP-CorV vaccine against COVID-19 in patients aged 60 years and older, during the Delta-dominant period, using a test-negative case-control design. Surveillance sites were 11 primary health care centers (PHC) collecting patient data from October 1, 2021, to January 4, 2022, retrospectively according to a common protocol. In total, we included 1711 participants in the analysis: 933 cases and 778 controls. Of the 933 cases, 508 (54.4 %) had mild and 425 (45.6 %) had moderate to severe disease presentation. We observed no effectiveness against mild COVID-19. Overall vaccine effectiveness was 65.0 % (95 %CI: 40.1-79.5) against moderate to severe COVID-19. In time since vaccination analysis, VE was 78.7 % (95 % CI: 54.8-89.9) in patients who received their last dose < 90 days before onset; 66.0 % (95 % CI: -0.5-88.5) in those 90-119 days before onset; 42.1 % (95 % CI: -88.6-82.3) in those 120-149 days before onset and 45.0 % (95 % CI: -94.0-84.4) in those ≥ 150 days before onset. In our study, two doses of BBIBP-CorV provided considerable protection against moderate to severe COVID-19 in older adults, highest within 3 months after second dose, during the Delta-dominant period. Point estimates declined thereafter, suggesting a need for additional doses.

Effectiveness of the BBIBP-CorV vaccine in preventing infection and death in health care workers in Peru 2021.

BACKGROUND: During 2021, Peru started the vaccination against SARS-CoV-2 using the BBIBP-CorV inactivated virus vaccine for health care workers (HCW). We aim to evaluate the effectiveness of the BBIBP-CorV vaccine to prevent SARS-CoV-2 infection and deaths among HCWs. METHODS: Retrospective cohort study, from February 9 to June 30, 2021, using national registries of health care workers, laboratory tests for SARS-CoV-2 and deaths. We calculated the vaccine effectiveness for preventing laboratory-confirmed SARS-CoV-2 infection, COVID-19-mortality, and all-cause mortality among partially immunized and fully immunized HCWs. An extension of Cox proportional hazards regression was used to model the mortality results, and Poisson regression was used to model SARS-CoV-2 infection. RESULTS: The study included 606,772 eligible HCWs, the mean age was 40 (IQR: 33.0, 51.0). In fully immunized HCW, the effectiveness for preventing all-cause mortality was 83.6 (95% CI: 80.2 to 86.4), 88.7 (95% CI: 85.1 to 91.4) for preventing COVID-19 mortality, and 40.3 (95% CI 38.9 to 41.6) for preventing SARS-CoV-2 infection. CONCLUSION: The BBIBP-CorV vaccine showed high levels of effectiveness for preventing all-cause and COVID-19 deaths among fully immunized HCW. These results were consistent within different subgroups and sensitivity analyses. However, the effectiveness for preventing infection was suboptimal in this particular setting.

Studying the effects of booster shots and antibody responses to the SARS-CoV-2 vaccination over time in health personnel.

Background: With the emergence of mutant versions that lead to continual spreading and recurrent infections of SARS-CoV-2, the COVID-19 vaccines can assist protection for high risk groups, particularly health workers. Even while booster shots have been widely used, longitude studies on immune responses in healthy subjects are uncommon. Methods: Eighty-five healthcare workers who received the BBIBP-CorV vaccine were prospectively enrolled and monitored for up to ten months. Automated Pylon immunoassays were used to quantify total anti-SARS-CoV2 antibody levels (TAb), surrogate neutralization antibody levels (NAb), and antibody avidities over the course of the follow-up. Additionally, hematology analyses were performed. Results: Pylon antibody testing revealed that every participant tested negative at the beginning, and 88.2% of them tested positive about 14 days after receiving their second dosage. The TAb levels and NAb levels peaked in 76.5% and 88.2% of the subjects, respectively, at the same time. Age was connected with the peak antibody levels, but not with gender, BMI, or baseline hematological factors. The positive rates and the antibody levels had already started to decline three months following the second injection. The antibody levels and avidities quickly increased following the booster doses to levels that were considerably greater than the peak antibody responses before to the booster shots. Hematology testing revealed no safety concerns with immunizations. Conclusion: In healthy workers, the two doses of BBIBP-CorV were able to induce humoral immunity; however, 3 months following vaccination, the antibody levels started to decline. The BBIBP-CorV booster injections increase both the quantity and quality of antibodies, which gave support for utilizing booster doses to prolong the duration of the vaccine's protective effects.

Predictors of immune persistence induced by two-dose BBIBP-CorV vaccine in high-risk occupational population.

BACKGROUND: The immune protection from infection may wane over time as neutralizing antibody levels decline. We aimed to develop a nomogram to predict long-term immune persistence induced by two-dose BBIBP-CorV vaccine and calculate the neutralizing antibody decline probability of individuals. METHODS: In the initial study, a total of 809 participants were recruited and randomly allocated (1:1:1) to vaccination group with three two-dose schedules on days 0 and 14, 0 and 21, or 0 and 28. The participants with neutralizing antibody titers of 16 or above on day 28 after the second dose were followed up at month 3, 6 and 10. Multivariable Cox proportional hazards regression model and nomogram model were used to identify predictors associated with maintaining of neutralizing antibody levels during 10 months after the second dose. RESULTS: A total of 744 participants followed up at day 28 after the second dose. The participants with age ≥ 50 (aHR = 3.556, 95 %CI: 1.141-4.884, P = 0.028) were associated with a high risk of response loss (titers < 16). The participants who were in 0-28 d group (aHR = 0.403, 95 %CI: 0.177-0.919, P = 0.031), had an influenza vaccination history (aHR = 0.468, 95 %CI: 0.267-0.921, P = 0.033) or were female (aHR = 0.542, 95 %CI: 0.269-0.935, P = 0.035) tended to maintain immune persistence during 10 months after the second dose. The nomogram was constructed and showed moderate discrimination[C-index:0.711 (95 %CI: 0.652-0.770); AUC: 0.731 (95 %CI: 0.663-0.792)] and good calibration. CONCLUSIONS: From 28 days to 10 months after receipt of the second dose of the BBIBP-CorV vaccine, neutralizing antibody levels were substantially decreased, especially among men, among persons 50 years of age or older, among persons with the 0-14 d group, and among persons without history of influenza vaccination. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR2100041705, ChiCTR2100041706.