Safety and Immunogenicity of a Second Dose of an Investigational Maternal Trivalent Group B Streptococcus Vaccine in Nonpregnant Women 4-6 Years After a First Dose: Results From a Phase 2 Trial

Background

Maternal immunization against group B streptococcus (GBS) could protect infants from invasive GBS disease. Additional doses in subsequent pregnancies may be needed. We evaluated the safety and immunogenicity of a second dose of an investigational trivalent CRM₁₉₇-glycoconjugate GBS vaccine (targeting serotypes Ia/Ib/III), administered to nonpregnant women 4–6 years postdose 1.

Methods

Healthy women either previously vaccinated with 1 dose of trivalent GBS vaccine 4–6 years before enrollment (n = 53) or never GBS vaccinated (n = 27) received a single trivalent GBS vaccine injection. Adverse events (AEs) were recorded. Serotype-specific (Ia/Ib/III) anti-GBS antibodies were measured by multiplex immunoassay prevaccination and 30/60 days postvaccination.

Results

AEs were reported with similar rates after a first or second dose; none were serious. Of previously GBS-vaccinated women, 92%–98% had anti-GBS concentrations that exceeded an arbitrary threshold (8 µg/mL) for each serotype 60 days postdose 2 vs 36%–56% postdose 1 in previously non–GBS-vaccinated women. Of previously GBS-vaccinated women with undetectable baseline (predose 1) anti-GBS levels, 90%–98% reached this threshold postdose 2. For each serotype, anti-GBS geometric mean concentrations (GMCs) 30/60 days postdose 2 in previously GBS-vaccinated women were ≥200-fold higher than baseline GMCs. Among women with undetectable baseline anti-GBS levels, postdose 2 GMCs in previously GBS-vaccinated women exceeded postdose 1 GMCs in previously non–GBS-vaccinated women (≥7-fold).

Conclusions

A second trivalent GBS vaccine dose administered 4–6 years postdose 1 was immunogenic with a favorable safety profile. Women with undetectable preexisting anti-GBS concentrations may benefit from a sufficiently spaced second vaccine dose.

Clinical Trials Registration

NCT02690181

Prevention of vaccine-matched and mismatched influenza in children aged 6-35 months: a multinational randomised trial across five influenza seasons

BACKGROUND

Despite the importance of vaccinating children younger than 5 years, few studies evaluating vaccine prevention of influenza have been reported in this age group. We evaluated efficacy of an inactivated quadrivalent influenza vaccine (IIV4) in children aged 6-35 months.

METHODS

In this phase 3, observer-blinded, multinational trial, healthy children from 13 countries in Europe, Central America, and Asia were recruited in five independent cohorts, each in a different influenza season. Participants were randomly assigned (1:1) to either IIV4 (15 μg haemagglutinin antigen per strain per 0·5 mL dose; a single dose on day 0 for vaccine-primed children, and two doses, on days 0 and 28, for vaccine-unprimed children) or to one or two doses of a non-influenza control vaccine. Primary endpoints were moderate-to-severe influenza or all influenza (irrespective of disease severity) confirmed by RT-PCR on nasal swabs. Cultured isolates were further characterised as antigenically matched or mismatched to vaccine strains. Efficacy was assessed in the per-protocol cohort and total vaccinated cohort (time-to-event analysis), and safety was assessed in the total vaccinated cohort.

FINDINGS

Between Oct 1, 2011, and Dec 31, 2014, 12 018 children were recruited into the total vaccinated cohort (6006 children in the IIV4 group and 6012 children in the control group). 356 (6%) children in the IIV4 group and 693 (12%) children in the control group had at least one case of RT-PCR-confirmed influenza. Of these 1049 influenza strains, 138 (13%) were A/H1N1, 529 (50%) were A/H3N2, 69 (7%) were B/Victoria, and 316 (30%) were B/Yamagata. Overall, 539 (64%) of 848 antigenically characterised isolates were vaccine-mismatched (16 [15%] of 105 for A/H1N1; 368 [97%] of 378 for A/H3N2; 54 [86%] of 63 for B/Victoria; 101 [33%] of 302 for B/Yamagata). Vaccine efficacy was 63% (97·5% CI 52-72) against moderate-to-severe influenza and 50% (42-57) against all influenza in the per-protocol cohort, and 64% (53-73) against moderate-to-severe influenza and 50% (42-57) against all influenza in the total vaccinated cohort. There were no clinically meaningful safety differences between IIV4 and control.

INTERPRETATION

IIV4 prevented influenza A and B in children aged 6-35 months despite high levels of vaccine mismatch. Vaccine efficacy was highest against moderate-to-severe disease, which is the most clinically important endpoint associated with greatest burden.

FUNDING

GlaxoSmithKline Biologicals SA.

Immunogenicity and safety of measles-mumps-rubella, varicella and Haemophilus influenzae type b vaccines administered concurrently with a fourth dose of heptavalent pneumococcal conjugate vaccine compared with the vaccines administered without heptavalent pneumococcal conjugate vaccine

BACKGROUND

Prevnar [heptavalent pneumococcal conjugate vaccine (PCV7)] is licensed in the United States for routine administration in infants and may be coadministered with other infant vaccines. Safety and immunogenicity data on the coadministration of the fourth dose of PCV7 with measles-mumps-rubella (MMR), varicella and Haemophilus influenzae type b (Hib) vaccines are limited.

METHODS

Children 12-15 months of age received either MMR with PCV7 (group 1) or MMR without PCV7 (group 2). All subjects received Hib and varicella vaccines. Group 2 received PCV7 6-9 weeks after MMR vaccination. Sera for analysis of all non-PCV7 antibodies were collected just before administration of MMR vaccine and 6 weeks later. Optimal antigen responses were assessed with the use of predetermined antibody titers. The primary end point was >90% response rate (all antigens). Noninferiority was defined as <10% difference between groups. Local and systemic reactions and postvaccination adverse events were monitored and compared between groups.

RESULTS

A total of 694 subjects (347 per group) were enrolled. After immunization with MMR plus PCV7 concurrently, or MMR followed 6 weeks later by PCV7, the percentages of subjects seroconverting were significantly greater than 90% for all antigens. The difference between the 2 groups was significantly less than 10%.

CONCLUSION

The immune response to MMR, Hib and varicella vaccines, when administered concurrently with a 4th (booster) dose of PCV7, was noninferior to that of these vaccines when given without PCV7. These results support concomitant administration of PCV7 with MMR, varicella and Hib as part of the recommended immunization schedule for children 12-15 months of age.

Relationship between serum bactericidal activity and serogroup-specific immunoglobulin G concentration for adults, toddlers, and infants immunized with Neisseria meningitidis serogroup C vaccines

A new meningococcal group C-CRM(197) conjugate vaccine (MnCC; Meningitec) has been evaluated in multiple clinical trials in the United States and most recently has been approved for routine administration in the United Kingdom. Meningococcal serogroup C (MnC)-specific immunoglobulin G (IgG) antibodies in pre- and postimmunization sera obtained from healthy U.S. adults, toddlers, and infants were quantitated by enzyme-linked immunosorbent assay (ELISA) and by an antibody-dependent, complement-mediated serum bactericidal assay (SBA). Serogroup-specific IgG antibody (micrograms per milliliter) in adults immunized either with the quadrivalent polysaccharide (A, C, Y, and W-135) vaccine or with MnCC showed a strong correlation (r = 0.848 and 0.934, respectively) by linear regression analysis with SBA. Sera from infants immunized with the MnCC (n = 30) and an age-matched unimmunized control group (n = 15) were also analyzed. Linear regression analysis of serum bactericidal and IgG ELISA data from sera obtained at 2 months of age (preimmunization) showed no correlation; however, a high degree of correlation was observed at time points after two (r = 0.877) and three (r = 0.951) immunizations, where significant rises in anti-MnC polysaccharide antibodies occurred relative to the age-matched control group. Infants previously primed with 3 doses of MnCC were given a booster dose of conjugate vaccine at 12 to 15 months of age. The correlation coefficient of ELISA to SBA for combined pre- and postbooster data was r = 0.836 (n = 48 pairs). In conclusion, increases in serum bactericidal activity in immunized adult, toddler, and infant populations were found to correlate very well with increases in serogroup-specific IgG concentrations, whereas the correlation between these two assays in nonimmunized 2-month-old infants was poor. Characterizing the relationship between these methods is important for understanding the significance of antigen-specific antibody concentrations relative to vaccine performance and protection from disease.

Biochemical and immunologic comparison of virus-like particles for a rotavirus subunit vaccine

A parenterally administered rotavirus vaccine composed of virus-like particles (VLPs) is being evaluated for human use. VLPs composed of bovine VP6 and simian VP7 (SA11, G3) proteins (6/7-VLPs) or of bovine VP2, bovine VP6, and simian VP7 (SA11, G3) proteins (2/6/7-VLPs) were synthesized and purified from Sf9 insect cells co-infected with recombinant baculoviruses. 6/7- and 2/6/7-VLP administered parenterally (i.m.) in mice had comparable immunogenicity, but the 2/6/7-VLPs were more homogeneous and stable. The inclusion of the VP2 capsid contributed to particle formation and stability. The adjuvant QS-21 significantly enhanced the immunogenicity of 2/6/7-VLPs over A10H or saline alone. Equivalent serum neutralizing antibody responses were induced over the range of 1-15 microg/dose of 2/6/7-VLPs administered with the range of 5-20 microg/dose of QS-21. The immunogenicity of 2/6/7-VLPs and inactivated SA11 virus were comparable. 2/6/7-VLPs are a promising candidate for a parenterally delivered rotavirus subunit vaccine.

Synthesis of rotavirus-like particles in insect cells: comparative and quantitative analysis

When the three major structural proteins, VP2, VP6, and VP7, of rotavirus are co-expressed in insect cells infected with recombinant baculoviruses, they self-assemble into triple-layered virus-like particles (VLPs) that are similar in morphology to native rotavirus. In order to establish the most favorable conditions for the synthesis of rotavirus VLPs, we have compared the kinetics of 2/6/7-VLP synthesis in two different insect cell lines: High Five cells propagated in Excell 405 medium and Spodoptera frugiperda 9 cells in Excell 400 medium. The majority of VLPs produced in both cell lines were released into the culture medium, and these released VLPs were predominantly triple-layered and were found to be stable for the period of six or seven days examined. The optimal synthesis of VLPs depended upon the cell line and the culture medium used as well as the time of harvesting infected cell cultures. The highest yield of VLPs was obtained from High Five cultures in the late phase of infection when the yield was at least 5-fold higher than that from S. frugiperda 9 cultures on a per cell basis. Our results demonstrate the usefulness of High Five cells for the production of VLPs as potential rotavirus subunit vaccines.

Virus-like particles as a rotavirus subunit vaccine

Rotavirus subunit vaccines are being evaluated for use in humans. The virus-like particles (VLPs) for these vaccines are produced in insect cells coinfected with combinations of baculovirus recombinants expressing bovine RIF VP2 and simian SA11, VP4, VP6, or VP7 rotavirus proteins. VLPs were administered parenterally to mice and rabbits, and the immunogenicity and protective efficacy of the vaccines were evaluated. Rabbits vaccinated with VP2/4/6/7 or VP2/6/7 VLP combinations developed high levels of rotavirus-specific serum antibody and fecal IgG but not fecal IgA. The induction of fecal IgG was associated with total or partial protection from oral challenge with ALA rotavirus. Heterotypic serum and fecal neutralizing antibody was induced in mice vaccinated parenterally with G1 VP2/6/7 or VP2/4/6n VLPs. VLPs were highly immunogenic when administered in QS21 adjuvant, inducing serum neutralizing antibody titers comparable to those induced by SA11 virus. VLPs are effective immunogens when administered parenterally and may be an effective subunit vaccine.