Immunogenicity and reactogenicity of primary immunization with a hexavalent diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated polio-Haemophilus influenzae type B vaccine coadministered with two doses of a meningococcal C-tetanus toxoid conjugate vaccine

Disparate kinetics in immune response of two different Haemophilus influenzae type b conjugate vaccines: Immunogenicity and safety observations from a randomized controlled phase IV study in healthy infants and toddlers using a 2+1 schedule

Since the introduction of Haemophilus Influenzae type b (Hib) conjugate vaccines, invasive Hib disease has strongly declined worldwide, yet continued control of Hib disease remains important. In Europe, currently three different hexavalent combination vaccines containing Hib conjugates are marketed. In this phase IV, single-blind, randomized, controlled, multi-country study (NCT04535037), we aimed to compare, in a 2 + 1 vaccination schedule, the immunogenicity and safety and show non-inferiority, as well as superiority, of DTPa-HBV-IPV/Hib (Ih group) versus DTaP5-HB-IPV-Hib (Va group) in terms of anti-polyribosylribitol phosphate (PRP) antibody geometric mean concentrations (GMCs) and proportion of participants reaching anti-PRP antibody concentrations greater than or equal to a threshold of 5 µg/mL. One month after the booster vaccination, the anti-PRP antibody GMC ratio (Ih group/Va group) was 0.917 (95% CI: 0.710-1.185), meeting the non-inferiority criteria. The difference in percentage of participants (Ih group - Va group) reaching GMCs ≥5 µg/mL was -6.3% (95% CI: -14.1% to 1.5%), not reaching the predefined non-inferiority threshold. Interestingly, a slightly higher post-booster antibody avidity was observed in the Ih group versus the Va group. Both vaccines were well tolerated, and no safety concerns were raised. This study illustrates the different kinetics of the anti-PRP antibody response post-primary and post-booster using the two vaccines containing different Hib conjugates and indicates a potential differential impact of concomitant vaccinations on the anti-PRP responses. The clinical implications of these differences should be further studied.

Immunogenicity and Safety of Childhood Combination Vaccines: A Systematic Review and Meta-Analysis

Background: Vaccination is considered the most effective and economical measure for controlling infectious diseases. Although combination vaccines are widely used worldwide, whether any of the combination vaccines is superior to each separate vaccine has yet to be established. This systematic review and meta-analysis aimed to summarize the available evidence on the effectiveness and safety of combination vaccines in children. Methods: A systematic search was conducted from database inception to August 20, 2021, in MEDLINE, Embase, Cochrane, and Scopus. Published randomized clinical trials (RCTs) and open-label trials of immunogenicity and safety of combined vaccines were selected. The results of the studies were quantitatively synthesized. Results: Overall, 25 articles met the inclusion criteria and were included in the meta-analysis. The results indicated that the combined diptheria−tetanus−acellular pertussis (DTaP)−hepatitis B virus (HBV)−Haemophilus influenzae type B (Hib) vaccine group had lower levels of anti-tetanus antibodies than the combined DTaP−HBV and separate Hib vaccinations group (SMD = −0.23; 95% CI: −0.42, −0.05; p = 0.013). Meanwhile, the combined DTaP−HBV−inactivated polio virus (IPV)−Hib vaccine group had higher levels of anti-pertussis (PT) and anti-filamentous hemagglutinin (FHA) antibodies than the combined DTaP−IPV−Hib and separate HBV vaccinations group (anti-PT: SMD = 0.60; 95% CI: 0.45, 0.75; p < 0.0001; anti-FHA: SMD = 0.40; 95% CI: 0.01, 0.78; p = 0.042). The levels of anti-pertactin (PRN) antibodies were lower in the combined DTaP−IPV−Hib vaccine group than in the combined DTaP−IPV and separate Hib vaccinations group (SMD = −0.13; 95% CI: −0.27, −0.00; p = 0.047). The individuals injected with the DTaP−HBV−IPV−Hib vaccine had a lower risk of pain and swelling than those injected with the combined DTaP−HBV−IPV and separate Hib vaccines (pain: RR = 0.79; 95% CI: 0.69, 0.91; p = 0.001; swelling: RR = 0.87; 95% CI: 0.78, 0.98; p = 0.020). However, the group that received the DTaP−HBV−IPV−Hib vaccine had a higher risk of fever than the group that received DTaP−HBV−IPV and separate Hib vaccinations (RR = 1.13; 95% CI: 1.02, 1.26; p = 0.021). Conclusions: This meta-analysis suggests that the combined vaccines (DTaP−IPV−Hib, DTaP−HBV−Hib, DTaP−HBV−IPV−Hib) are safe, well-tolerated, and provide immunogenic alternatives to separate vaccines in children. The combined DTaP−HBV−IPV−Hib vaccine showed a higher incidence of fever, which was lower than the cumulative incidence of fever induced by all vaccines. Future studies should evaluate the cost-effectiveness of using combined vaccines and compare the potency of different formulations to improve routine local or national childhood immunization programs.

Infant vaccine co-administration: review of 18 years of experience with GSK's hexavalent vaccine co-administered with routine childhood vaccines

INTRODUCTION

The benefits of vaccine co-administration include improved vaccine acceptance and uptake resulting in an increased coverage and protection against multiple childhood diseases, with minimal medical visits. The diphtheria-tetanus-acellular pertussis-hepatitis B-poliomyelitis-Haemophilus influenzae type b vaccine (DTaP-HBV-IPV/Hib) has been available for more than 19 years and is recommended for co-administration with several other infant vaccines.

AREAS COVERED

This is a comprehensive review (34 studies, 21,000 participants) describing the immunogenicity and safety of DTaP-HBV-IPV/Hib when co-administered with 12 different vaccines in infants including pneumococcal, meningococcal, rotavirus or measles-mumps-rubella-varicella.

EXPERT OPINION

Interactions among co-administered vaccines are complex. Therefore, co-administration data are critical before a vaccination regimen can be recommended. Co-administration of DTaP-HBV-IPV/Hib with other routinely administered vaccines was associated with high percentages of children achieving seroprotection/vaccine response against DTaP-HBV-IPV/Hib antigens. In addition, co-administration was not associated with clinically significant interference in immune responses to co-administered vaccines and was well tolerated. Increased systemic reactions observed with some combinations (DTaP-HBV-IPV/Hib + pneumococcal conjugate or meningococcal serogroup B vaccines) were mitigated by prophylactic paracetamol administration. The data reported here, which represent the most frequently used co-administrations of DTaP-HBV-IPV/Hib worldwide, support the concomitant administration of DTaP-HBV-IPV/Hib with other routinely recommended infant vaccines.

Immunogenicity and safety of an adjuvanted inactivated polio vaccine, IPV-Al, following vaccination in children at 2, 4, 6 and at 15-18 months

BACKGROUND

Availability of affordable inactivated polio vaccines (IPV) is of major importance to meet the increasing global supply needs. The results presented here demonstrate non-inferiority of a reduced-dose, aluminium hydroxide-adjuvanted IPV (IPV-Al) to standard IPV.

METHODS

A phase 3, observer-blinded, randomised, clinical trial was conducted in Panama in infants who received either IPV-Al (n = 400) or standard IPV (n = 400) at age 2, 4 and 6 months. In the booster trial, subjects received a single dose of IPV-Al at age 15-18 months. The primary endpoint was type-specific seroconversion, defined as an antibody titre ≥4-fold higher than the estimated maternal antibody titre and a titre ≥8, one month after the primary vaccination series. In the booster trial, the primary endpoint was the type-specific booster effects (geometric mean titre (GMT) post-booster (Day 28)/GMT pre-booster (Day 0).

RESULTS

Seroconversion rates following primary vaccination with IPV-Al vs IPV were: 96.1% vs 100% (type 1); 100% vs 100% (type 2); and 99.2% vs 100% (type 3) respectively. IPV-Al was non-inferior to IPV, as the lower 95% confidence limits of the treatment differences were above the pre-defined -10%-point limit: 3.94% (-6.51; -2.01) for type 1; 0.0% (-1.30; -1.37) for type 2; -0.85 (-2.46; 0.40) for type 3. The booster effects for the group primed with IPV-Al versus the group primed with IPV were 25.3 vs 9.2 (type 1), 19.1 vs 6.5 (type 2) and 50.4 vs 12.5 (type 3). IPV-Al had a comparable safety profile to that of IPV.

CONCLUSIONS

Non-inferiority of IPV-Al to standard IPV with respect to seroconversion after vaccination at 2, 4 and 6 months was confirmed for all three poliovirus serotypes. A robust booster response was demonstrated following vaccination with IPV-Al, regardless of the primary vaccine received. Both vaccines were well tolerated. ClinicalTrials.gov identifiers: NCT03025750 and NCT03671616.

FUNDING

Bill & Melinda Gates Foundation.

New perspectives for hexavalent vaccines

With the increase in the number of routine vaccinations the development of pentavalent and hexavalent combination vaccines fitting the routine vaccination schedules became a necessity. In this respect, Europe has taken the lead in comparison with other world regions, and routine vaccination with pentavalent and hexavalent combinations including DTPa, Hib, HepB and IPV has been on European vaccination programs for >15years. Since the marketing authorization of Hexavac® and Infanrix Hexa® in 2000, immunization schedules in most European countries have included hexavalent vaccines. In the last years, two new hexavalent vaccines have been licensed and commercialized worldwide. This paper presents a review of the pharmaceutical profiles of the three hexavalent vaccines currently available. In addition, we aim to review safety, co-administration, tolerability and other practical concerns of their use.

The Influence of Maternally Derived Antibody and Infant Age at Vaccination on Infant Vaccine Responses : An Individual Participant Meta-analysis

IMPORTANCE

The design of infant immunization schedules requires an understanding of the factors that determine the immune response to each vaccine antigen.

DATA SOURCES

Deidentified individual participant data from GlaxoSmithKline clinical trials were obtained through Clinical Study Data Request. The data were requested on January 2, 2015, and final data were received on April 11, 2016.

STUDY SELECTION

Immunogenicity trials of licensed or unlicensed vaccines administered to infants were included if antibody concentrations in infants were measured prior to the first dose of vaccine.

DATA EXTRACTION AND SYNTHESIS

The database was examined; studies that appeared to have appropriate data were reviewed.

MAIN OUTCOMES AND MEASURES

Antigen-specific antibody concentration measured 1 month after priming vaccine doses, before booster vaccination, and 1 month after booster vaccine doses.

RESULTS

A total of 7630 infants from 32 studies in 17 countries were included. Mean (SD) age at baseline was 9.0 (2.3) weeks; 3906 (51.2%) were boys. Preexisting maternal antibody inhibited infant antibody responses to priming doses for 20 of 21 antigens. The largest effects were observed for inactivated polio vaccine, where 2-fold higher maternal antibody concentrations resulted in 20% to 28% lower postvaccination antibody concentration (geometric mean ratios [GMRs], type 1: 0.80; 95% CI, 0.78-0.83; type 2: 0.72; 95% CI, 0.69-0.74; type 3: 0.78; 95% CI, 0.75-0.82). For acellular pertussis antigens, 2-fold higher maternal antibody was associated with 11% lower postvaccination antibody for pertussis toxoid (GMR, 0.89; 95% CI, 0.87-0.90) and filamentous hemagglutinin (GMR, 0.89; 95% CI, 0.88-0.90) and 22% lower pertactin antibody (GMR, 0.78; 95% CI, 0.77-0.80). For tetanus and diphtheria, these estimates were 13% (GMR, 0.87; 95% CI, 0.86-0.88) and 24% (GMR, 0.76; 95% CI, 0.74-0.77), respectively. The influence of maternal antibody was still evident in reduced responses to booster doses of acellular pertussis, inactivated polio, and diphtheria vaccines at 12 to 24 months of age. Children who were older when first immunized had higher antibody responses to priming doses for 18 of 21 antigens, after adjusting for the effect of maternal antibody concentrations. The largest effect was seen for polyribosylribitol phosphate antibody, where responses were 71% higher per month (GMR, 1.71; 95% CI, 1.52-1.92).

CONCLUSIONS AND RELEVANCE

Maternal antibody concentrations and infant age at first vaccination both influence infant vaccine responses. These effects are seen for almost all vaccines contained in global immunization programs and influence immune response for some vaccines even at the age of 24 months. These data highlight the potential for maternal immunization strategies to influence established infant programs.

Immunogenicity and safety of 3-dose primary vaccination with combined DTPa-HBV-IPV/Hib in Indian infants

Multivalent combination vaccines have reduced the number of injections and therefore improved vaccine acceptance, timeliness of administration and global coverage. The hexavalent diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated poliovirus/Haemophilus influenzae type b (DTPa-HBV-IPV/Hib; Infanrix hexa™) vaccine, administered according to various schedules, is widely used for the primary vaccination of infants worldwide. In the current publication, we are presenting the immunogenicity and safety of 3 doses of DTPa-HBV-IPV/Hib vaccine when administered to Indian infants. 224 healthy infants (mean age 6.8 weeks) were vaccinated at 6-10-14 weeks (W) of age (n = 112) or 2-4-6 months (M) of age (n = 112). One month after the third vaccine dose, the seroprotection/seropositivity status against diphtheria, pertussis, tetanus, polio, hepatitis B and Hib antigens ranged from 98.6% to 100% in both groups. The vaccine response rate to the pertussis antigens ranged from 97% to 100%. Pain (6-10-14W group: 25.2%; 2-4-6M group: 13.4%) and fever (15.3% and; 15.2%, respectively) were the most frequently reported solicited local and general symptoms. Unsolicited adverse events were reported for 35.7% (6-10-14W group) and 22.3% (2-4-6M group) of subjects. No vaccine related serious adverse events were reported. In conclusion, the hexavalent DTPa-HBV-IPV/Hib vaccine was immunogenic and well tolerated, irrespective of the dosing schedule.

The impact of administration of conjugate vaccines containing cross reacting material on Haemophilus influenzae type b antibody responses in infants: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Protein-polysaccharide conjugate vaccines such as Haemophilus influenzae type b (Hib), meningococcal, and pneumococcal vaccine, induce immunological memory and longer lasting protection than plain polysaccharide vaccines. The most common proteins used as carriers are tetanus toxoid (TT) and cross reacting material-197 (CRM), a mutant form of diphtheria toxoid. CRM conjugate vaccines have been reported to suppress antibody responses to co-administered Hib-TT vaccine.

METHODS

We conducted a systematic review and meta-analysis of randomised controlled trials in which infants were randomised to receive meningococcal or pneumococcal conjugate vaccines along with Hib-TT. Trials of licensed vaccines with different carrier proteins were included for group C meningococcal (MenC), quadrivalent ACWY meningococcal (MenACWY), and pneumococcal vaccines.

RESULTS

Twenty-three trials were included in the meta-analyses. Overall, administration of MenC-CRM in a 2 or 3 dose schedule resulted in a 45% reduction in Hib antibody concentrations (GMR 0.55, 95% CI 0.49-0.62). MenACWY-CRM boosted Hib antibody responses by 22% (GMR 1.22, 95% CI 1.06-1.41) whilst pneumococcal CRM conjugate vaccines had no impact on Hib antibody responses (GMR 0.91, 95% CI 0.68-1.22).

CONCLUSIONS

The effect of CRM protein-polysaccharide conjugate vaccines on Hib antibody responses varies greatly between vaccines. Co-administration of a CRM conjugate vaccine can produce either positive or negative effects on Hib antibody responses. These inconsistencies suggest that CRM itself may not be the main driver of variability in Hib responses, and challenge current perspectives on this issue.

Combination vaccines against diarrheal diseases

Diarrheal diseases remain a leading cause of global childhood mortality and morbidity. Several recent epidemiological studies highlight the rate of diarrheal diseases in different parts of the world and draw attention to the impact on childhood growth and survival. Despite the well-documented global burden of diarrheal diseases, currently there are no combination diarrheal vaccines, only licensed vaccines for rotavirus and cholera, and Salmonella typhi-based vaccines for typhoid fever. The recognition of the impact of diarrheal episodes on infant growth, as seen in resource-poor countries, has spurred action from governmental and non-governmental agencies to accelerate research toward affordable and effective vaccines against diarrheal diseases. Both travelers and children in endemic countries will benefit from a combination diarrheal vaccine, but it can be argued that the greater proportion of any positive impact will be on the public health status of the latter. The history of combination pediatric vaccines indicate that monovalent or single disease vaccines are typically licensed first prior to formulation in a combination vaccine, and that the combinations themselves undergo periodic revision in response to need for improvement in safety or potential for wider coverage of important pediatric pathogens. Nevertheless combination pediatric vaccines have proven to be an effective tool in limiting or eradicating communicable childhood diseases worldwide. The landscape of diarrheal vaccine candidates indicates that there now several in active development that offer options for potential testing of combinations to combat those bacterial and viral pathogens responsible for the heaviest disease burden—rotavirus, ETEC, Shigella, Campylobacter, V. cholera and Salmonella.

Update on the use of meningococcal serogroup C CRM₁₉₇-conjugate vaccine (Meningitec) against meningitis

Meningitec is a CRM197-conjugated meningococcal serogroup C (MenC) vaccine, first licensed in 1999. It has been used as a primary and booster vaccine in infants, toddlers, older children and adults, and has been shown to be immunogenic and well-tolerated in all age groups, including premature infants. Vaccine effectiveness has been demonstrated using combined data on all three licensed MenC conjugate vaccines. Evidence from clinical trials, however, suggests that the different MenC conjugate vaccines behave differently with respect to the induction and persistence of bactericidal antibody and generation of immune memory. It appears that Meningitec has a less favorable immunologic profile compared particularly to tetanus toxoid (TT) MenC conjugate vaccines. Data from comparative trials have raised interesting questions on priming of the immune system by conjugate vaccines, particularly in infants. The results from these and other studies are reviewed here with specific focus on Meningitec.

[Is it ethically acceptable to invite a pregnant woman to enroll in a clinical trial with Tdap if it could entail not being vaccinated with Tdap before delivery?]

Pertussis incidence has increased in recent years, especially among infants aged <2months. A number of Spanish regions have started a vaccination program with Tdap vaccine to all pregnant women in the third trimester of pregnancy. An observational study has shown that this strategy reduces the number of cases of pertussis by 90% in infants aged <2months. Mathematical models showed that a cocooning strategy (i.e. vaccination of the mother at immediate postpartum, and other adults and adolescents who have close contact with the newborn and caregivers) will reduce the incidence of pertussis by 70% in infants aged <2months. It is intended to conduct a clinical trial in which 340 pregnant women will receive Tdap vaccine, whereas another 340 pregnant woman will be vaccinated soon after delivery. Vaccination with Tdap will be offered to all partners and caregivers of the newborn. After assessing both the ethical and scientific reasons supporting the trial, it is concluded that it is ethically and legally acceptable to invite pregnant women living in communities where Tdap vaccination has been implemented to participate in the trial.

Long-term persistence of immunity and B-cell memory following Haemophilus influenzae type B conjugate vaccination in early childhood and response to booster

BACKGROUND

Protection against Haemophilus influenzae type b (Hib), a rapidly invading encapsulated bacteria, is dependent on maintenance of an adequate level of serum antibody through early childhood. In many countries, Hib vaccine booster doses have been implemented after infant immunization to sustain immunity. We investigated the long-term persistence of antibody and immunological memory in primary-school children following infant (with or without booster) Hib vaccination.

METHODS

Anti-polyribosylribitol phosphate (PRP) immunoglobulin G (IgG) concentration and the frequency of circulating Hib-specific memory B cells were measured before a booster of a Hib-serogroup C meningococcal (MenC) conjugate vaccine and again 1 week, 1 month, and 1 year after the booster in 250 healthy children aged 6-12 years in an open-label phase 4 clinical study.

RESULTS

Six to 12 years following infant priming with 3 doses of Hib conjugate vaccine, anti-PRP IgG geometric mean concentrations were 3.11 µg/mL and 0.71 µg/mL and proportions with anti-PRP IgG ≥1.0 µg/mL were 79% and 43% in children who had or had not, respectively, received a fourth Hib conjugate vaccine dose (mean age, 3.9 years). Higher baseline and post-Hib-MenC booster responses (anti-PRP IgG and memory B cells) were found in younger children and in those who had received a fourth Hib dose.

CONCLUSIONS

Sustained Hib conjugate vaccine-induced immunity in children is dependent on time since infant priming and receipt of a booster. Understanding the relationship between humoral and cellular immunity following immunization with conjugate vaccines may direct vaccine design and boosting strategies to sustain individual and population immunity against encapsulated bacteria in early childhood. Clinical Trials Registration ISRCTN728588998.

Combined hexavalent diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated poliovirus-Haemophilus influenzae type B vaccine; Infanrix™ hexa: twelve years of experience in Italy

Infant vaccination using 2-dose priming at 3 and 5 mo of age with a booster at 11–12 mo of age was pioneered in Italy. The 3-5-11 schedule is now used in a growing number of European countries. Infanrix™ hexa (DTPa-HBV-IPV/Hib, GlaxoSmithKline Vaccines) was first licensed for use in 2000 and has been the only pediatric hexavalent vaccine available since 2005. We reviewed available clinical trial data describing the immunogenicity of DTPa-HBV-IPV/Hib when administered at 3, 5, and 11 mo of age, and conducted an analysis of safety using global and Italian post-marketing surveillance data. In Italy, DTPa-HBV-IPV/Hib has a demonstrated safety record extending over a decade of use, it has been associated with record levels of vaccine coverage, and with sustained disease control in vaccinated cohorts. Hexavalent vaccines will continue to contribute to high vaccine coverage in Italy and across Europe.

Effectiveness of meningococcal serogroup C vaccine programmes

Since the introduction of monovalent meningococcal serogroup C (MenC) glycoconjugate (MCC) vaccines and the implementation of national vaccination programmes, the incidence of MenC disease has declined markedly as a result of effective short-term vaccination and reduction in acquisition of MenC carriage leading to herd protection. Monovalent and quadrivalent conjugate vaccines are commonly used vaccines to provide protection against MenC disease worldwide. Studies have demonstrated that MCC vaccination confers protection in infancy (0-12 months) from the first dose but this is only short-term. NeisVac-C(®) has the greatest longevity of the currently licensed MCC vaccines in terms of antibody persistence, however antibody levels have been found to fall rapidly after early infant vaccination with two doses of all MCC vaccines - necessitating a booster at ∼12 months. In toddlers, only one dose of the MCC vaccine is required for routine immunization. If herd protection wanes following catch-up campaigns, many children may become vulnerable to infection. This has led many to question whether an adolescent booster is also required.

Phase II study of a three-dose primary vaccination course of DTPa-IPV/Hib-MenC-TT followed by a 12-month Hib-MenC-TT booster in healthy infants

AIM

To test for immunologic noninferiority of antibody responses to Hib and MenC using a 6-in-1 combination vaccine (DTPa-IPV/Hib-MenC-TT) compared with DTPa-IPV-Hib plus MenC-CRM197, before and after a 12-month Hib-MenC-TT booster.

METHODS

Pragmatic open-label, randomized, multicenter, UK study. "6-in-1" group received DTPa-IPV/Hib-MenC-TT at 2, 3 and 4 months; control group received DTPa-IPV-Hib at 2, 3 and 4 months and MenC-CRM197 at 3 and 4 months. Both groups received Hib-MenC-TT at 12 months. Concomitant vaccines: pneumococcal conjugate vaccine at 2, 4 and 13 months, and measles, mumps and rubella vaccine at 13 months.

RESULTS

One hundred forty-two children were randomized to each group. One hundred children in the "6-in-1" group and 112 control group children completed the study according-to-protocol. One month postprimary immunizations: 100% of "6-in-1" group and 93.3% of control children had anti-polyribosylribitol phosphate (PRP) IgG ≥0.15 µg/mL; 96.2% and 100%, respectively, had rSBA-MenC titers ≥1:8. One month after booster all children met these thresholds, with anti-PRP geometric mean concentrations of 66.7 (53.3; 83.5) in "6-in-1" recipients and 26.9 (20.9; 34.6) in control children (4.4 [3.5; 5.4] and 3.0 [2.2-4.2] postprimary immunizations, respectively,). rSBA-MenC geometric mean titers were 3062.9 (2421.2; 3874.6) and 954.0 (761.3; 1195.5), respectively, postbooster and 393.2 (292.5; 528.7) and 3110.5 (2612; 3704.2) postprimary.

CONCLUSION

Noninferiority of DTPa-IPV/Hib-MenC-TT compared with DTPa-IPV/Hib plus MenC-CRM197 was demonstrated. In the "6-in-1" group, lower postprimary and greater postbooster rSBA-MenC geometric mean titers suggest memory B-cell priming may be favored by this vaccine over plasma cell induction. Furthermore, greater immunogenicity of TT conjugates used in both primary and booster vaccines in this group may be important.

DTPa-HBV-IPV/Hib vaccine (Infanrix hexa™): a guide to its use in infants

Infanrix hexa™, a diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliomyelitis, and Haemophilus influenzae type b (Hib) conjugate vaccine, is indicated for primary and booster vaccination of infants. Available clinical data from more than a decade of experience with the vaccine indicate that primary and booster vaccination with Infanrix hexa™ is a safe and useful option for providing protection against the common childhood diseases of diphtheria, tetanus, poliomyelitis, pertussis, hepatitis B, and disease caused by Hib.

Glycoconjugate vaccines and immune interactions, and implications for vaccination schedules

Conjugate vaccines using diphtheria toxoid variant (CRM(197)), diphtheria toxoid and tetanus toxoid (TT) as carrier protein may induce immune interactions (interference or impairment as measured by lower antibody levels, or enhancement [higher antibody levels]) when coadministered with other vaccines. Immune enhancement occurs when two TT conjugates are coadministered. CRM(197) conjugate vaccines induce immune bystander interference when given with diphtheria-tetanus-acellular pertussis vaccines, which reduces responses to coadministered Haemophilus influenzae type b vaccine conjugated to TT. These bystander effects are greater as the amount of CRM(197) administered increases. When large amounts of either TT or CRM(197) are coadministered, dose-related carrier-induced epitopic suppression may occur, affecting immune responses to meningococcal or pneumococcal polysaccharides. These observations have implications for vaccine scheduling. The range of available alternative vaccines means that specific vaccine coadministrations can avoid or reduce CRM(197)-induced interference. Potential interactions arising from new CRM(197) or TT conjugates will need to be thoroughly examined.

Effect of increased CRM₁₉₇ carrier protein dose on meningococcal C bactericidal antibody response

New multivalent CRM(197)-based conjugate vaccines are available for childhood immunization. Clinical studies were reviewed to assess meningococcal group C (MenC) antibody responses following MenC-CRM(197) coadministration with CRM(197)-based pneumococcal or Haemophilus influenzae type b conjugate vaccines. Infants receiving a total CRM(197) carrier protein dose of ∼50 μg and concomitant diphtheria-tetanus-acellular pertussis (DTaP)-containing vaccine tended to have lower MenC geometric mean antibody titers and continued to have low titers after the toddler dose. Nevertheless, at least 95% of children in the reported studies achieved a MenC serum bactericidal antibody (SBA) titer of ≥ 1:8 after the last infant or toddler dose. SBA was measured using an assay with a baby rabbit or human complement source. Additional studies are needed to assess long-term antibody persistence and MenC CRM(197) conjugate vaccine immunogenicity using alternative dosing schedules.

Combination vaccines

The combination of diphtheria, tetanus, and pertussis vaccines into a single product has been central to the protection of the pediatric population over the past 50 years. The addition of inactivated polio, Haemophilus influenzae, and hepatitis B vaccines into the combination has facilitated the introduction of these vaccines into recommended immunization schedules by reducing the number of injections required and has therefore increased immunization compliance. However, the development of these combinations encountered numerous challenges, including the reduced response to Haemophilus influenzae vaccine when given in combination; the need to consolidate the differences in the immunization schedule (hepatitis B); and the need to improve the safety profile of the diphtheria, tetanus, and pertussis combination. Here, we review these challenges and also discuss future prospects for combination vaccines.

A randomized, multicenter, open-label clinical trial to assess the immunogenicity of a meningococcal C vaccine booster dose administered to children aged 14 to 18 months

BACKGROUND

A booster meningococcal C (MenC) vaccine dose is recommended after the first year of life. The objective of this study was to assess its immunogenicity and factors that modify the immunoresponse.

METHODS

An open label study in which 389 children 14 to 18 months of age, previously primed with 3 doses of a MenC vaccine conjugated with CRM197 (MenC-CRM) or with 2 doses of a MenC vaccine conjugated with tetanus toxoid (MenC-TT), were randomized to be boosted with either of these vaccines and a DTaP-IPV-Hib vaccine at the same time. Immunogenicity against MenC and Haemophilus influenzae type b was assessed before and 1 month after the booster dose.

RESULTS

Before the second year booster, 44.9% of the studied children had MenC bactericidal (SBA) seroprotection rate of > or =1:8, with no differences related to the vaccine used for priming, whereas the anti Hib antibody concentration was higher in children primed with the MenC-TT (0.59; 95% CI: 0.49-0.71 vs. 0.39; 95% CI: 0.32-0.48).One month after the MenC vaccine booster 99.5% of the children had SBA > or =1:128. Children primed with MenC-TT reached higher SBA titers: 6520 (95% CI: 5359-7932) than those primed with MenC-CRM: 1903 (95% CI: 1600-2262). Children primed with MenC-CRM had SBA titers of 2061 (95% CI: 1599-2627) when boosted with MenC-TT and 1746 (95% CI: 1378-2213) when boosted with MenC-CRM. Children primed with MenC-TT had SBA titers of 6786 (95% CI: 5023-9167) and 6278 (95% CI: 4841-8144) when boosted with MenC-TT or MenC-CRM. There was no difference in the PRP antibody concentration after boosting.

CONCLUSIONS

A booster MenC dose induces high SBA and anti Hib response with over 99% of children seroprotected. Children primed with a MenC-TT vaccine reached SBA titers 3.5 times higher no matter which vaccine was used for boosting.

Immunogenicity of a 2-dose priming and booster vaccination with the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine

BACKGROUND

The immunogenicity of the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) was determined following a simplified 2-dose priming and the more commonly employed 3-dose priming both followed by a booster dose.

METHODS

A total of 351 healthy subjects were primed with PHiD-CV at either 3 and 5 or 3, 4 and 5 months of age followed in all subjects by a booster dose at 11 to 12 months of age. Serotype-specific pneumococcal responses were measured by 22F-inhibition ELISA and opsonophagocytic assays 1 month following primary and booster vaccinations.

RESULTS

Depending on the serotype, the percentages of subjects reaching the ELISA antibody threshold of 0.2 microg/mL were 92.8% to 98.0% following 2 primary doses and 96.1% to 100% following 3 primary doses except for serotype 6B (55.7% and 63.1%, respectively) and serotype 23F (69.3% and 77.6%, respectively). Opsonophagocytic activity (OPA) could be measured in 74.4% to 100% and 88.9% to 100% of the subjects after the 2-dose or 3-dose priming, respectively, except for serotype 1 (60.8% and 62.9%, respectively). In both groups, robust increases in ELISA antibodies and OPA titers were observed for all serotypes after the booster dose. Higher postprimary and postbooster ELISA antibody levels and OPA titers were observed for most serotypes following the 3+1 schedule.

CONCLUSION

PHiD-CV was immunogenic in both schedules, but further effectiveness data are needed to fully understand the public health benefit to be expected from these schedules in terms of prevention against invasive and mucosal infections.

Review of 8 years of experience with Infanrix hexa (DTPa-HBV-IPV/Hib hexavalent vaccine)

Combination vaccines that include multiple antigens within one formulation are now widely accepted as an effective means of eliciting protection against several diseases at the same time. Owing to improvements in quality and convenient modes of administration, they have become part of routine pediatric practice. Hexavalent vaccines, including diphtheria, tetanus, pertussis, hepatitis B, polio and Haemophilus influenzae type b antigens represent the latest advance in the development of combination vaccines. Over 8 years since its first licensure, this review looks at the immunogenicity, efficacy and safety profile of the only hexavalent pediatric vaccine currently in use--Infanrix hexa (diphtheria, tetanus, acellular pertusis-hepatitis B virus-inactivated poliovirus vaccine/Haemophilus influenzae type b vaccine [DTPa-HBV-IPV/Hib]; GlaxoSmithKline Biologicals, Rixensart, Belgium)--through published clinical trials and postmarketing surveillance data. These data show DTPa-HBV-IPV/Hib to be highly immunogenic and well tolerated across a range of different primary and booster vaccination schedules, as well as when administered concomitantly with other licensed vaccines (e.g., pneumococcal conjugate vaccine). Additional issues surrounding the use of hexavalent vaccines are also reviewed.

Immunogenicity of routinely used childhood vaccines when coadministered with the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV)

BACKGROUND

The choice of non-typeable Haemophilus influenzae Protein D as main carrier protein in the candidate 10-valent pneumococcal conjugate vaccine (PHiD-CV, GlaxoSmithKline Biologicals), was driven in part to avoid carrier-mediated suppression and possible bystander interference with coadministered vaccines. Immunogenicity data from 3 primary and 2 booster vaccination studies were assessed for possible impacts of PHiD-CV coadministration on immune responses to routinely administered childhood vaccines, in comparison to 7-valent pneumococcal conjugate vaccine (7vCRM) coadministration.

METHODS

Randomized, controlled studies in which PHiD-CV or 7vCRM vaccines were coadministered with DTPa-[HBV]-IPV/Hib, DTPa-[HBV]-IPV, DTPw-HBV/Hib, IPV, and OPV, combined Hib-Neisseria meningitidis serogroup C vaccine (Hib-MenC-TT), standalone MenC-TT or MenC-CRM vaccines.

RESULTS

One month after primary vaccination, >96% of PHiD-CV recipients had seroprotective antibody concentrations against diphtheria, tetanus, poliovirus types 1 and 3, Hib (>or=0.15 microg/mL), SBA-MenC (>or=1:8), and >94% were seropositive for antibodies against pertussis antigens. Somewhat lower responses against poliovirus type 2 in study A (compared with poliovirus type 1 and 2 responses) and hepatitis B in the 6-, 10-, and 14-week schedule in the Philippines (compared with hepatitis B responses in the other studies) were observed after coadministration of both PHiD-CV and 7vCRM vaccines. Antitetanus and anti-PRP antibody geometric mean concentrations (GMCs) tended to be higher after PHiD-CV coadministration, probably because of the TT carrier protein for serotype 18C in PHiD-CV. Booster vaccination induced substantial increases in antibody GMCs for all coadministered antigens. These responses were generally within the same range in PHiD-CV and 7vCRM groups. Observed anti-PRP responses remained higher in PHiD-CV recipients after the booster dose.

CONCLUSIONS

Coadministration of PHiD-CV with commonly used childhood vaccines induced high levels of seroprotection/seropositivity against all targeted diseases. No evidence of negative interference on the immune response to any of the coadministered vaccine antigens was observed when compared with the current routine practice of 7vCRM coadministration.

Concomitant use of the 3-dose oral pentavalent rotavirus vaccine with a 3-dose primary vaccination course of a diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated polio-Haemophilus influenzae type b vaccine: immunogenicity and reactogenicity

BACKGROUND

The pentavalent rotavirus vaccine (PRV), RotaTeq, can be concomitantly administered with most routine childhood vaccines. This study evaluated the immunogenicity and reactogenicity of PRV when used concomitantly with a hexavalent vaccine containing diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus, and Haemophilus influenzae type b.

METHODS

Healthy infants (N = 403) received hexavalent vaccine concomitantly with either PRV or placebo at 2, 3, and 4 months of age. Antibody responses were measured immediately before and 42 +/- 3 days after vaccination. Parents/legal guardians recorded all adverse events for 14 days after vaccination.

RESULTS

Seroprotective titers for hepatitis B (hepatitis B surface antigen > or =10 mIU/mL) were achieved by 97.8% of subjects in both vaccine treatment groups. Seroprotective titers to H. influenzae type b (polyribosylribitol phosphate > or =0.15 microg/mL) were achieved by 91.4% of subjects receiving both vaccines and 95.1% of subjects receiving only hexavalent vaccine. Seroprotective titers to diphtheria, tetanus, and poliovirus were also comparable between the vaccine treatment groups, as were geometric mean antibody titers to the pertussis antigens. Among PRV recipients, 92% had a > or =3-fold rise in serum antirotavirus immunoglobulin A levels. Concomitant administration was well tolerated. The incidence of adverse events was similar for both groups, with no statistically significant increases in fever, vomiting, diarrhea, or irritability.

CONCLUSIONS

In this study, concomitant administration of PRV with hexavalent vaccine was well tolerated and the immune responses to the antigens of the hexavalent vaccine were noninferior when compared with those of the control group. In addition, PRV was immunogenic when administered concomitantly with hexavalent vaccine.

Immunogenicity of a reduced schedule of meningococcal group C conjugate vaccine given concomitantly with the Prevenar and Pediacel vaccines in healthy infants in the United Kingdom

This study investigated the use of two doses of three different meningococcal group C conjugate (MCC) vaccines when given for primary immunization with a seven-valent pneumococcal conjugate vaccine (PCV7) and Pediacel, a combination product containing five acellular pertussis components, diphtheria and tetanus toxoids, Haemophilus influenzae type b (Hib) conjugate, and inactivated-poliovirus vaccine. The immune response after a single dose of MCC is also presented. Infants were randomized to receive two doses of one of the MCC vaccines and PCV7 at 2 and 3 months or at 2 and 4 months of age. Meningococcal group C serum bactericidal antibody (SBA) geometric mean titers, Hib-polyribosylribitol phosphate (PRP) immunoglobulin G (IgG) geometric mean concentrations (GMCs), and diphtheria and tetanus antitoxin GMCs, together with the proportions of infants achieving putative protective levels, were determined. A total of 393 infants were recruited. Following the first dose of NeisVac-C (MCC conjugated to tetanus toxoid), 97% of infants achieved protective levels (SBA titer of >or=8), compared with 80% and 53%, respectively, for Menjugate and Meningitec (both of which are conjugated to CRM(197)). SBA responses to MCC vaccines were not significantly different when administered at 2 and 3 or 2 and 4 months of age. Following two doses of each MCC, 98 to 100% of infants achieved protective levels. Both PRP IgG and tetanus responses were significantly enhanced when Pediacel was coadministered with NeisVac-C. This study demonstrates that NeisVac-C and Menjugate generate good immunogenicity after the first dose at 2 months of age when coadministered with PCV7 and Pediacel and merit further investigation in single-dose priming strategies.

Immunogenicity and reactogenicity of a booster dose of a novel combined Haemophilus influenzae type b-Neisseria meningitidis serogroup C-tetanus toxoid conjugate vaccine given to toddlers of 13-14 months of age with antibody persistence up to 31 months of age

BACKGROUND

A combined Haemophilus influenzae type b and Neisseria meningitidis serogroup C tetanus toxoid conjugate vaccine (Hib-MenC-TT) may be a convenient alternative to separate Hib and MenC conjugate vaccines.

METHODS

Healthy infants randomized in a previous study for priming at 2, 4, and 6 months: Hib-MenC-TT primed group, 3 doses of Hib-MenC-TT + DTPa-HBV-IPV (N = 87); MenC-TT primed group, 2 doses of MenC-TT (NeisVac-C; Baxter Healthcare SA, Zuürich, Switzerland) + 3 doses of DTPa/Hib containing vaccines (N = 178); MenC-CRM primed group, 3 doses of MenC-CRM197(Meningitec; Wyeth Corporation Delaware, Madison, NJ) + DTPa-HBV-IPV/Hib (N = 93). At 13-14 months of age, Hib-MenC-TT and MenC-TT primed groups received a Hib-MenC-TT booster dose and the MenC-CRM primed group a booster dose of DTPa-HBV-IPV/Hib. Blood samples were taken before and at 1 and 18 months postbooster.

RESULTS

Before the booster dose, persistence of anti-polyribosyl ribitol phosphate (PRP) antibody concentration > or =0.15 microg/mL in the Hib-MenC-TT (96.4%) and MenC-TT (96.1%) primed groups and of MenC bactericidal titers > or =1:8 in the Hib-MenC-TT primed group (96.3%) was statistically significantly higher than in the MenC-CRM primed group (86.4% and 85.4%, respectively). One month after the Hib-MenC-TT booster, 99.2% subjects in the Hib-MenC-TT primed + MenC-TT primed pooled groups had anti-PRP levels > or =1 microg/mL, and 99.6% had SBA-MenC titers > or =1:128. The Hib-MenC-TT booster tended to be less reactogenic than the DTPa-HBV-IPV/Hib control and no serious adverse events related to vaccination were reported. Eighteen months after boosting with Hib-MenC-TT, SBA-MenC titers > or =1:8 persisted in 92.7% subjects and anti-PRP > or =0.15 microg/mL persisted in 99.4%.

CONCLUSIONS

Primary immunization with 3 doses of Hib-MenC-TT coadministered with DTPa-HBV-IPV induced antibodies that persisted up to the second year of life. The Hib-MenC-TT booster administered to primed toddlers induced robust and persistent antibody responses to both the Hib and MenC components and had an acceptable safety profile.

Adverse events following immunization: perception and evidence

PURPOSE OF REVIEW

The aim of this article is to highlight the evidence on new and ongoing vaccine safety concerns in the light of several vaccines recently licensed and others made available and recommended more widely.

RECENT FINDINGS

There is increasingly convincing epidemiologic and laboratory evidence against a causal relation of several alleged adverse events following immunization. The scientific framework to detect and investigate adverse events following immunization is increasingly robust.

SUMMARY

Currently available vaccines are safe in immunocompetent individuals and there is no evidence to deviate from current immunization schedules.

Immunogenicity, safety and tolerability of meningococcal C CRM197 conjugate vaccine administered 3, 5 and 11 months post-natally to pre- and full-term infants

A total of 79 pre-term infants with a gestational age > or =32 weeks and 74 full-term infants were studied in order to evaluate the immunogenicity, safety and tolerability of meningococcal C (MenC)-CRM(197) conjugate vaccine administered 3, 5 and 11 months post-natally. The evoked immune response seemed to be substantially similar in the pre- and full-term infants, and there were only clinically marginal differences in safety and tolerability between the groups. The results support the use of two doses of MenC-CRM(197) vaccine at 3 and 5 months of age for primary immunisation, with a booster dose being given at about 1 year. In addition to reducing costs, this scheme seems to assure global immunogenicity and potential efficacy that is better than that offered by the accelerated scheme of administration with only three doses of vaccine in the first months of life, and similar to that observed with a fourth dose used as booster after the first year.

Immunogenicity and reactogenicity of primary immunization with a novel combined Haemophilus influenzae Type b and Neisseria meningitidis Serogroup C-tetanus toxoid conjugate vaccine coadministered with a Diphtheria-tetanus-acellular Pertussis-hepatitis B-inactivated poliovirus vaccine at 2, 4 and 6 months

BACKGROUND

This phase II study evaluated the immunogenicity and reactogenicity of primary vaccination with a novel Hib-MenC conjugate vaccine (GlaxoSmithKline [GSK] Biologicals) coadministered with DTPa-HBV-IPV (GSK Biologicals) at 2, 4 and 6 months.

METHODS

Healthy infants were randomized to receive Hib-MenC coadministered with DTPa-HBV-IPV (N = 117) or MenC-CRM (Wyeth) coadministered with DTPa-HBV-IPV/Hib (GSK Biologicals; N = 120) at 2, 4 and 6 months. Antibody concentrations were measured before vaccination and after doses 2 and 3. Solicited local and general symptoms, unsolicited symptoms and serious adverse events (SAEs) were recorded.

RESULTS

All subjects in the Hib-MenC group had seroprotective titers of anti-PRP antibodies (>or=0.15 microg/mL) and SBA-MenC titers (>or=1:8) 1 month after the third dose. These responses were noninferior to those seen in the control group, in which a 99.1% seroprotection rate was observed for both Hib and MenC. At that time, anti-PRP and SBA-MenC GMTs were significantly higher in the Hib-MenC group (12.8 microg/mL and 2467.1 microg/mL, respectively) than in the control group (3.8 microg/mL and 1833.7 microg/mL). High seroprotection rates were already observed after the second dose of Hib-MenC; 96.4% and 100% of subjects were seroprotected to Hib and MenC, respectively. Immune responses to coadministered antigens were unimpaired; seroprotection/vaccine response rates >or=96.5% were recorded postdose 3 in the Hib-MenC group. No differences in reactogenicity were seen between the 2 study groups.

CONCLUSIONS

Coadministration of a Hib-MenC conjugate vaccine with DTPa-HBV-IPV is well tolerated and immunogenic, and does not impair the immune response to any of the coadministered antigens.