Immunogenicity and Safety of a Purified Vero Rabies Vaccine-Serum Free, Compared With 2 Licensed Vaccines, in a Simulated Rabies Post-Exposure Regimen in Healthy Adults in France: A Randomized, Controlled, Phase 3 Trial.

BACKGROUND: A next-generation Vero cell rabies vaccine (PVRV-NG2) was developed using the same Pitman-Moore strain as in the licensed purified Vero cell vaccine (PVRV; Verorab) and the human diploid cell vaccine (HDCV; Imovax Rabies®). METHODS: This dual-center, modified, double-blind, phase 3 study evaluated the immunogenic non-inferiority and safety of PVRV-NG2 with and without concomitant intramuscular human rabies immunoglobulin (HRIG) versus PVRV + HRIG and HDCV + HRIG in a simulated post-exposure prophylaxis (PEP) regimen. Healthy adults ≥18 years old (N = 640) were randomized 3:1:1:1 to PVRV-NG2 + HRIG, PVRV + HRIG, HDCV + HRIG, or PVRV-NG2 alone (administered as single vaccine injections on days [D] 0, D3, D7, D14, and 28, with HRIG on D0 in applicable groups). Rabies virus neutralizing antibodies (RVNA) titers were assessed pre- (D0) and post-vaccination (D14, D28, and D42) using the rapid fluorescent focus inhibition test. Non-inferiority, based on the proportion of participants achieving RVNA titers ≥0.5 IU/mL (primary objective), was demonstrated if the lower limit of the 95% CI of the difference in proportions between PVRV-NG2 + HRIG and PVRV + HRIG/HDCV + HRIG was >-5% at D28. Safety was assessed up to 6 months after the last injection. RESULTS: Non-inferiority of PVRV-NG2 + HRIG compared with PVRV + HRIG and HDCV + HRIG was demonstrated. Nearly all participants (99.6%, PVRV-NG2 + HRIG; 100%, PVRV + HRIG; 98.7%, HDCV + HRIG; 100%, PVRV-NG2 alone) achieved RVNA titers ≥0.5 IU/mL at D28. Geometric mean titers were similar between groups with concomitant HRIG administration at all time points. Safety profiles were similar between PVRV-NG2 and comparator vaccines. CONCLUSIONS: In a simulated PEP setting, PVRV-NG2 + HRIG showed comparable immunogenicity and safety to current standard-of-care vaccines. CLINICAL TRIALS REGISTRATION: NCT03965962.

Safety and immunogenicity of a serum-free purified Vero rabies vaccine in comparison with the rabies human diploid cell vaccine (HDCV; Imovax® Rabies) administered in a simulated rabies post-exposure regimen in healthy adults.

A new generation, serum-free, antibiotic-free, purified Vero rabies vaccine (PVRV-NG; Sanofi) has been developed based on the same Pitman-Moore viral strain used for the currently licensed purified Vero cell rabies vaccine (PVRV; Verorab®, Sanofi) and human diploid cell vaccine (HDCV; Imovax® Rabies, Sanofi). PVRV-NG has demonstrated a satisfactory safety profile and induces robust immune responses, with non-inferiority demonstrated versus PVRV when given as a three-dose pre-exposure prophylaxis (PrEP) regimen in healthy children and adults. Here, we evaluated the safety and immunogenic non-inferiority of PVRV-NG compared to HDCV when administered as simulated post-exposure prophylaxis (PEP), with concomitant administration of human rabies immunoglobulin (HRIG), in healthy adults in the USA. Participants were vaccinated according to the 5-dose Essen intramuscular regimen (4-week, 1-injection site regimen, with a single dose given on days 0, 3, 7, 14 and 28) for PEP, with concomitant HRIG administered on day 0. Rabies virus neutralising antibodies (RVNA) were evaluated on days 0, 14, 28 and 42. Non-inferiority of PVRV-NG compared with HDCV was shown if the lower limit of the 95 % confidence interval (CI) for the difference in seroconversion rates (RVNA titers ≥ 0.5 IU/mL on day 14) between PVRV-NG and HDCV was above the non-inferiority margin of -5 %. Safety was evaluated after each vaccination and monitored throughout the study. The difference in seroconversion rate between the PVRV-NG and HDCV groups was -2.8 % (95 % CI, -8.08 to 4.20), indicating that non-inferiority was not demonstrated. The seroconversion rate was < 99 % in both study groups on day 14. There were no major safety concerns identified, and PVRV-NG demonstrated a similar safety profile to HDCV.

Safety and immunogenicity of three dose levels of an investigational, highly purified Vero cell rabies vaccine: A randomized, controlled, observer-blinded, Phase II study with a simulated post-exposure regimen in healthy adults.

A serum-free, highly purified rabies vaccine produced in Vero cells is under development. The initial formulation, PVRV-NG, was evaluated in five Phase II studies and subsequently reformulated (PVRV-NG2). This multicenter, observer-blinded Phase II study investigated the safety and immune response of three different doses (antigen content) of PVRV-NG2 versus a licensed human diploid cell rabies vaccine (HDCV; Imovax rabies®). Healthy adults (N = 320) were randomized to receive PVRV-NG2 (low, medium, or high dose), PVRV-NG, or HDCV (2:2:2:1:1 ratio), according to a five-dose Essen simulated post-exposure regimen (Days [D] 0, 3, 7, 14, and 28). All participants received human rabies immunoglobulin intramuscularly on D0. Immunogenicity was assessed at D0, 14, 28, 42, and 6 months after the final injection using the rapid fluorescent focus inhibition test. Seroconversion rates were calculated as the percentage of participants achieving rabies virus neutralizing antibody titers ≥0.5 IU/mL. All analyses were descriptive. At each timepoint, geometric mean titers (GMTs) increased with antigen content (measured using an enzyme-linked immunosorbent assay). High-dose PVRV-NG2 GMTs were the highest at all timepoints, medium-dose PVRV-NG2 GMTs were similar to those with HDCV, and low-dose PVRV-NG2 GMTs were similar to PVRV-NG. The safety profile of PVRV-NG2 was comparable to PVRV-NG; however, fewer injection site reactions were reported with PVRV-NG2 or PVRV-NG (range 36.7-47.5%) than with HDCV (61.5%). This study demonstrated a dose-effect of antigen content at all timepoints. As post-exposure prophylaxis, the safety and immunogenicity profiles of the high-dose PVRV-NG2 group compared favorably with HDCV. Clinicaltrials.gov number: NCT03145766.

Safety and immunogenicity of a serum-free purified Vero rabies vaccine in healthy adults: A randomised phase II pre-exposure prophylaxis study.

A serum-free, highly purified Vero cell rabies vaccine (PVRV-NG) is under development. We previously demonstrated that pre-exposure prophylaxis (PrEP) with PVRV-NG had a satisfactory safety profile and was immunogenically non-inferior to the licensed purified Vero cell rabies vaccine in adults. Here, we evaluated the safety and immunogenic non-inferiority of PrEP with PVRV-NG compared to the licensed human diploid cell vaccine (HDCV) in healthy adults (NCT01784874). Participants received three vaccinations (days 0, 7, and 28) as PrEP with or without a booster injection after 12 months. Rabies virus neutralising antibodies (RVNA) were evaluated on days 0, 28 (subgroup only), and 42, and Months 6, 12, and 12 + 14 days (booster group only). Non-inferiority (first primary objective) was based on the proportion of participants with RVNA titres ≥ 0.5 IU/mL (World Health Organization criteria for seroconversion) on day 42, expected to be ≥ 99% (second primary objective). Safety was evaluated after each dose and monitored throughout the study. At day 42, PVRV-NG was non-inferior to HDCV and the first primary objective was met; seroconversion was observed for 98.3% of PVRV-NG recipients and 99.1% of HDCV recipients. As < 99% of participants in the PVRV-NG group had RVNA titres ≥ 0.5 IU/mL, the second primary objective was not met. Booster vaccination produced a strong increase in RVNA titres for all groups, primed with PVRV-NG or HDCV. RVNA geometric mean titres tended to be higher for HDCV than PVRV-NG primary vaccine recipients. In a complementary evaluation using alternative criteria for seroconversion (complete virus neutralization at 1:5 serum dilution), 99.6% and 100% of participants in the PVRV-NG and HDCV groups, respectively, achieved seroconversion across the vaccine groups. No major safety concerns were observed during the study. PVRV-NG was well tolerated, with a similar safety profile to HDCV in terms of incidence, duration, and severity of adverse events after primary and booster vaccinations. ClinicalTrials.gov number: NCT01784874.

Serum-free purified Vero rabies vaccine is safe and immunogenic in children: Results of a randomized phaseII pre-exposure prophylaxis regimen study.

BACKGROUND: A serum-free, highly purified Vero rabies vaccine (PVRV-NG) has been developed with no animal or human components and low residual DNA content. A phaseII randomized clinical study aimed to demonstrate the non-inferiority of the immune response and assess the safety profile of PVRV-NG versus a licensed human diploid cell culture rabies vaccine (HDCV) in a pre-exposure regimen in healthy children and adolescents in the Philippines. METHODOLOGY: Children aged 2-11 years and adolescents aged 12-17 years were randomized (2:1) to receive three injections of either PVRV-NG or HDCV (on day [D] 0, D7 and D28). Rabies virus-neutralizing antibodies (RVNA) were measured at D0, D42 and 6 months after the first injection (month [M] 6). Safety was assessed during the vaccination period and up to 28 days after the last vaccination. Serious adverse events were followed until 6 months after last vaccination. PRINCIPAL FINDINGS: 342 healthy participants (171 children and 171 adolescents) were randomized and followed for 6 months after the last dose. All participants in both groups had an RVNA titer ≥ 0.5 IU/ml at D42, demonstrating non-inferiority in seroconversion rate for PVRV-NG versus HDCV. Over 90% of participants had RVNA titer ≥ 0.5 IU/ml at M6. PVRV-NG was well tolerated after each vaccination and up to 6 months following the last dose. There were no major safety concerns during the study, and the type and severity of solicited adverse events was similar for both treatment groups. CONCLUSIONS: This study demonstrated the non-inferior immune profile of PVRV-NG compared with HDCV in a pre-exposure setting within a pediatric population. PVRV-NG was well tolerated with no safety concerns. This study is registered at ClinicalTrials.gov (NCT01930357) and EU Clinical Trials Register (2015-003203-30).

Seronegative patients vaccinated with cytomegalovirus gB-MF59 vaccine have evidence of neutralising antibody responses against gB early post-transplantation.

BACKGROUND: Human cytomegalovirus (HCMV) causes a ubiquitous infection which can pose a significant threat for immunocompromised individuals, such as those undergoing solid organ transplant (SOT). Arguably, the most successful vaccine studied to date is the recombinant glycoprotein-B (gB) with MF59 adjuvant which, in 3 Phase II trials, demonstrated 43-50% efficacy in preventing HCMV acquisition in seronegative healthy women or adolescents and reduction in virological parameters after SOT. However, the mechanism of vaccine protection in seronegative recipients remains undefined. METHODS: We evaluated samples from the cohort of seronegative SOT patients enroled in the Phase II glycoprotein-B/MF59 vaccine trial who received organs from seropositive donors. Samples after SOT (0-90 days) were tested by real-time quantitative PCR for HCMV DNA. Anti-gB antibody levels were measured by ELISA. Neutralization was measured as a decrease in infectivity for fibroblast cell cultures revealed by expression of immediate-early antigens. FINDINGS: Serological analyses revealed a more rapid increase in the humoral response against gB post transplant in vaccine recipients than in those randomised to receive placebo. Importantly, a number of patient sera displayed HCMV neutralising responses - neutralisation which was abrogated by pre-absorbing the sera with recombinant gB. INTERPRETATION: We hypothesise that the vaccine primed the immune system of seronegative recipients which, when further challenged with virus at time of transplant, allowed the host to mount rapid immunological humoral responses even under conditions of T cell immune suppression during transplantation.

Protection from cytomegalovirus viremia following glycoprotein B vaccination is not dependent on neutralizing antibodies.

Human cytomegalovirus (HCMV) is an important pathogen in transplant patients and in congenital infection. Previously, we demonstrated that vaccination with a recombinant viral glycoprotein B (gB)/MF59 adjuvant formulation before solid organ transplant reduced viral load parameters post transplant. Reduced posttransplant viremia was directly correlated with antibody titers against gB consistent with a humoral response against gB being important. Here we show that sera from the vaccinated seronegative patients displayed little evidence of a neutralizing antibody response against cell-free HCMV in vitro. Additionally, sera from seronegative vaccine recipients had minimal effect on the replication of a strain of HCMV engineered to be cell-associated in a viral spread assay. Furthermore, although natural infection can induce antibody-dependent cellular cytotoxicity (ADCC) responses, serological analysis of seronegative vaccinees again presented no evidence of a substantial ADCC-promoting antibody response being generated de novo. Finally, analyses for responses against major antigenic domains of gB following vaccination were variable, and their pattern was distinct compared with natural infection. Taken together, these data argue that the protective effect elicited by the gB vaccine is via a mechanism of action in seronegative vaccinees that cannot be explained by neutralization or the induction of ADCC. More generally, these data, which are derived from a human challenge model that demonstrated that the gB vaccine is protective, highlight the need for more sophisticated analyses of new HCMV vaccines over and above the quantification of an ability to induce potent neutralizing antibody responses in vitro.

Epitope-Specific Humoral Responses to Human Cytomegalovirus Glycoprotein-B Vaccine With MF59: Anti-AD2 Levels Correlate With Protection From Viremia.

The human cytomegalovirus (HCMV) virion envelope protein glycoprotein B (gB) is essential for viral entry and represents a major target for humoral responses following infection. Previously, a phase 2 placebo-controlled clinical trial conducted in solid organ transplant candidates demonstrated that vaccination with gB plus MF59 adjuvant significantly increased gB enzyme-linked immunosorbent assay (ELISA) antibody levels whose titer correlated directly with protection against posttransplant viremia. The aim of the current study was to investigate in more detail this protective humoral response in vaccinated seropositive transplant recipients. We focused on 4 key antigenic domains (AD) of gB (AD1, AD2, AD4, and AD5), measuring antibody levels in patient sera and correlating these with posttransplant HCMV viremia. Vaccination of seropositive patients significantly boosted preexisting antibody levels against the immunodominant region AD1 as well as against AD2, AD4, and AD5. A decreased incidence of viremia correlated with higher antibody levels against AD2 but not with antibody levels against the other 3 ADs. Overall, these data support the hypothesis that antibodies against AD2 are a major component of the immune protection of seropositives seen following vaccination with gB/MF59 vaccine and identify a correlate of protective immunity in allograft patients.

Safety and efficacy of a cytomegalovirus glycoprotein B (gB) vaccine in adolescent girls: A randomized clinical trial.

BACKGROUND: Cytomegalovirus (CMV) is a leading cause of congenital infection and an important target for vaccine development. METHODS: CMV seronegative girls between 12 and 17 years of age received CMV glycoprotein B (gB) vaccine with MF59 or saline placebo at 0, 1 and 6 months. Blood and urine were collected throughout the study for evidence of CMV infection based on PCR and/or seroconversion to non-vaccine CMV antigens. RESULTS: 402 CMV seronegative subjects were vaccinated (195 vaccine, 207 placebo). The vaccine was generally well tolerated, although local and systemic adverse events were significantly more common in the vaccine group. The vaccine induced gB antibody in all vaccine recipients with a gB geometric mean titer of 13,400 EU; 95%CI 11,436, 15,700, after 3 doses. Overall, 48 CMV infections were detected (21 vaccine, 27 placebo). In the per protocol population (124 vaccine, 125 placebo) vaccine efficacy was 43%; 95%CI: -36; 76, p=0.20. The most significant difference was after 2 doses, administered as per protocol; vaccine efficacy 45%, 95%CI: -9; 72, p=0.08. CONCLUSION: The vaccine was safe and immunogenic. Although the efficacy did not reach conventional levels of significance, the results are consistent with a previous study in adult women (Pass et al. N Engl J Med 2009;360:1191) using the same formulation.

A next-generation, serum-free, highly purified Vero cell rabies vaccine is safe and as immunogenic as the reference vaccine Verorab® when administered according to a post-exposure regimen in healthy children and adults in China.

BACKGROUND: As an evolution of its currently licensed rabies vaccine Verorab(®), Sanofi Pasteur has developed a next-generation, serum-free, highly purified Vero rabies vaccine (PVRV-NG). Through this Phase III clinical trial, we aimed to demonstrate the non-inferiority of PVRV-NG over Verorab when administered according to a post-exposure regimen and to assess its clinical safety. METHODS: A total of 816 healthy subjects aged ≥10 years were randomized according to a 2:1 ratio to receive PVRV-NG or Verorab. Half of the subjects were aged 10-17 years, the other half were aged ≥18 years. All subjects were to receive 5 injections on days 0, 3, 7, 14 and 28. Three blood samples were taken for rabies virus neutralizing antibodies (RVNA) assessment, at baseline, on day 14 and day 42. Solicited adverse reactions (between injections 1, 2 and 3, and within 7 days post-injections 4 and 5) and adverse events (up to 28 days after the last injection) were collected for clinical safety assessment; serious adverse events were reported up to 6-months after the last injection. RESULTS: The proportion of subjects with an RVNA titer ≥0.5 IU/mL after the third injection of PVRV-NG was non-inferior to the proportion of those who received Verorab. PVRV-NG was shown to be as immunogenic as Verorab in each age range in the per-protocol and full analysis sets. PVRV-NG induced a strong immune response in both age ranges, with high RVNA levels and increased geometric mean titers compared to baseline after each measured time point. PVRV-NG had a satisfactory safety profile after each injection, similar to Verorab with regards to the nature, frequency, duration and severity of adverse events. Two serious adverse events were reported, none was related to vaccination. CONCLUSIONS: This trial demonstrated the immunogenic non-inferiority of PVRV-NG over Verorab and showed that both vaccines have similar safety profiles. This trial is registered at ClinicalTrials.gov (NCT01339312). This manuscript is the first full report of the study. An abstract of the study results was previously presented at the Rabies in the Americas (RITA) conference in October 2012 in São Paulo, Brazil. FUNDING: Sanofi Pasteur.

A serum-free, purified vero cell rabies vaccine is safe and as immunogenic as the reference vaccine Verorab for pre-exposure use in healthy adults: results from a randomized controlled phase-II trial.

BACKGROUND: Verorab was licensed in 1985 for both pre- and post-exposure prophylaxis of rabies. The next generation purified Vero cell rabies vaccine (PVRV-NG) is a highly purified vaccine. We performed a phase II clinical study in adults in France to assess its immunological non-inferiority and clinical safety for pre-exposure prophylaxis. METHODS: In a randomized phase-II trial, 384 healthy adult subjects were randomized (2:1) to receive a three-dose primary series of PVRV-NG or Verorab. One year later, the PVRV-NG group received a PVRV-NG booster while the Verorab group participants were randomized to receive a booster of PVRV-NG or Verorab for. Rabies virus neutralizing antibodies (RVNA) were evaluated on days 0, 28 (subgroup), 42, months 6, 12 and 12+14 days. Safety was evaluated for seven days after each dose. Adverse event between doses, until 28 days after the final dose was recorded. Serious adverse events were recorded up to 6 months after the last dose. RESULTS: The criterion for non-inferiority was met in the per-protocol analysis set and confirmed in the full analysis set (FAS). In the FAS, 99.6% and 100% of subjects had RVNA titers ≥0.5 IU/mL in PVRV-NG and Verorab groups, respectively. While RVNA levels gradually decreased over the 12-month period, at 6 and 12 months after vaccination >89% and >77%, respectively, in both groups had RVNA titers ≥0.5 IU/mL. The PVRV-NG booster induced a strong response, irrespective of the vaccine given for the primary series. PVRV-NG was safe and well tolerated and its safety profile was similar to Verorab for unsolicited adverse events and solicited systemic reactions. The incidence of solicited injection-site reactions was lower with PVRV-NG than with Verorab after the primary series and the booster dose. CONCLUSIONS: PVRV-NG was shown to be at least as immunogenic as Verorab and to present a similar safety profile.

Glycoprotein B vaccine is capable of boosting both antibody and CD4 T-cell responses to cytomegalovirus in chronically infected women.

Traditionally, vaccines have been utilized to generate immune responses to a pathogen in a naive population. In the setting of congenital cytomegalovirus (CMV) infection, a vaccine that, when administered to women already infected with CMV, could boost the mother's immunity to CMV would most likely be beneficial in diminishing in utero transmission of CMV. However, the ability to boost an immune response in a population of individuals seropositive for a pathogen of interest is not well studied. This study examines the ability of a recombinant CMV glycoprotein B vaccine with MF59 adjuvant to boost both antibody (neutralizing and enzyme-linked immunosorbent assay end point dilution titer) and CD4+ T-cell responses in previously CMV-seropositive women by way of natural infection. These data suggest that this vaccine is capable of boosting immunity in a population of CMV-infected women and warrants additional evaluation to determine whether these boosted responses may prevent mother to child transmission of CMV.

Cytomegalovirus glycoprotein-B vaccine with MF59 adjuvant in transplant recipients: a phase 2 randomised placebo-controlled trial.

BACKGROUND: Cytomegalovirus end-organ disease can be prevented by giving ganciclovir when viraemia is detected in allograft recipients. Values of viral load correlate with development of end-organ disease and are moderated by pre-existing natural immunity. Our aim was to determine whether vaccine-induced immunity could do likewise. METHODS: We undertook a phase-2 randomised placebo controlled trial in adults awaiting kidney or liver transplantation at the Royal Free Hospital, London, UK. Exclusion criteria were pregnancy, receipt of blood products (except albumin) in the previous 3 months, and simultaneous multiorgan transplantation. 70 patients seronegative and 70 seropositive for cytomegalovirus were randomly assigned from a scratch-off randomisation code in a 1:1 ratio to receive either cytomegalovirus glycoprotein-B vaccine with MF59 adjuvant or placebo, each given at baseline, 1 month and 6 months later. If a patient was transplanted, no further vaccinations were given and serial blood samples were tested for cytomegalovirus DNA by real-time quantitative PCR (rtqPCR). Any patient with one blood sample containing more than 3000 cytomegalovirus genomes per mL received ganciclovir until two consecutive undetectable cytomegalovirus DNA measurements. Safety and immunogenicity were coprimary endpoints and were assessed by intention to treat in patients who received at least one dose of vaccine or placebo. This trial is registered with ClinicalTrials.gov, NCT00299260. FINDINGS: 67 patients received vaccine and 73 placebo, all of whom were evaluable. Glycoprotein-B antibody titres were significantly increased in both seronegative (geometric mean titre 12,537 (95% CI 6593-23,840) versus 86 (63-118) in recipients of placebo recipients; p<0.0001) and seropositive (118,395; 64,503-217,272) versus 24,682 (17,909-34,017); p<0.0001) recipients of vaccine. In those who developed viraemia after transplantation, glycoprotein-B antibody titres correlated inversely with duration of viraemia (p=0.0022). In the seronegative patients with seropositive donors, the duration of viraemia (p=0.0480) and number of days of ganciclovir treatment (p=0.0287) were reduced in vaccine recipients. INTERPRETATION: Although cytomegalovirus disease occurs in the context of suppressed cell-mediated immunity post-transplantation, humoral immunity has a role in reduction of cytomegalovirus viraemia. Vaccines containing cytomegalovirus glycoprotein B merit further assessment in transplant recipients. FUNDING: National Institute of Allergy and Infectious Diseases, Grant R01AI051355 and Wellcome Trust, Grant 078332. SPONSOR: University College London (UCL).

An adjuvanted, low-dose, pandemic influenza A (H5N1) vaccine candidate is safe, immunogenic, and induces cross-reactive immune responses in healthy adults.

BACKGROUND: To protect a naive global population against pandemic influenza, pandemic vaccines should be effective at low antigen doses, because of limited manufacturing capacity. METHODS: In a multicenter, randomized, blind-observer phase 1 trial, groups of 50 healthy young adults received 2 doses, 21 days apart, of influenza A/Vietnam/1194/2004 NIBRG-14 (H5N1) vaccine containing 1.9, 3.8, 7.5 or 15 microg of hemagglutinin with oil-in-water emulsion adjuvant or 7.5 microg of hemagglutinin without adjuvant. Safety was monitored to day 42. Homologous hemagglutination-inhibition (HI) and microneutralization titers were determined after each vaccination. Cross-reactivity against A/Indonesia/05/2005 RG2 was tested after the second vaccination. RESULTS: No vaccine-related significant or serious adverse events occurred. Injection site reactions, but not systemic reactions, were more frequent with adjuvant than without. Even with only 1.9 microg of hemagglutinin plus adjuvant, 72% of subjects had HI titers >or=1:32 after 2 doses. This proportion was 81%-89% with higher adjuvanted doses but was only 34% without adjuvant. Adjuvanted vaccine induced cross-neutralizing antibodies in 39%-65% of samples, versus 7% without adjuvant. CONCLUSIONS: The emulsion-adjuvanted pandemic influenza vaccine candidate was safe, immunogenic, and induced cross-reactive antibodies. This adjuvanted 1.9-microg candidate is the lowest effective dose tested to date. This could have a major impact on prepandemic vaccination strategies with stockpiled batches of vaccine. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00457509 .

Immunological priming of one dose of inactivated hepatitis A vaccine given during the first year of life in presence of maternal antibodies.

BACKGROUND: In hepatitis A virus (HAV)-seronegative infants, inactivated hepatitis A vaccines are highly immunogenic. On the contrary, in infants who are HAV-seropositive before vaccination, the interfering effect of passively-transferred maternal anti-HAV antibodies leads to lower post-primary immunization anti-HAV levels, as compared to those achieved by seronegative infants. One possible way to overcome this drawback is to delay hepatitis A vaccination later during the first year of life. The objective of the study was to document the immunogenicity of an inactivated hepatitis A vaccine in 6 months old HAV-seropositive infants, given as two dose regimen consisting of a single primary immunization at 6 months of age, followed by a booster dose 6 months later. METHODS: The immunogenicity of one hepatitis A vaccine (Avaxim pediatric, Aventis Pasteur) was documented in 108 6 months old, HAV-seropositive infants randomly assigned to receive one priming dose of hepatitis A vaccine either concomitantly with (Group 2) or 2 weeks after the third dose of routine diphteria-tetanus-whole cell pertussis reconstituting lyophilized tetanus conjugated Haemophilus influenzae type b (DTwcP//PRP approximately T) vaccine and oral poliomyelitis vaccine (OPV) (Group 1). A booster dose was given 6 months later, concomitantly with MMR vaccine. RESULTS: The 91 infants who were HAV-seropositive (ELISA titer >20 mIU/ml) at the moment of primo vaccination remained seropositive 1 month later. Geometric mean titers (GMT) decreased from 292 and 278 mIU/ml 1 month after the first dose, to 77.6 and 76.0 mIU/ml 6 months after, in Groups 1 and 2, respectively. Post-booster titers increased markedly in both groups, with GMTs of 1731 and 1866 mIU/ml and geometric mean post/pre-immunization titer ratios of 22.3 and 24.6, respectively. CONCLUSIONS: These results suggest that immunological priming induced by a single dose of Avaxim pediatric administered to 6 or 6.5 months old, HAV-seropositive infants is present and should not preclude the use of this vaccine in such populations.