Strategies for development of combination vaccines

The value of childhood combination vaccines: From beliefs to evidence

Although vaccination is one of the most cost-effective health care interventions, under-vaccination and variation in coverage rates lower than policy targets is rising in developed countries, partly due to concerns about vaccination value and benefits. By merging various antigens into a single product, combination vaccines represent a valuable tool to mitigate the burden associated with the numerous injections needed to protect against vaccine preventable infectious diseases and increase coverage rate, possibly through various behavioral mechanisms which have yet to be fully explored. Beyond their cost-effectiveness in protecting against more diseases with fewer injections, combination vaccines also have several other benefits, for children, their parents/carers, as well as for the health system and the population as a whole. The objectives of this review are to identify and illustrate the value of combination vaccines for childhood immunization. Evidence was classified into 2 groups: benefits for society and benefits for public health and healthcare systems. This article also highlights the value of innovation and challenges of combination vaccine development as well as the need for an increased number of suppliers to mitigate the impact of any potential vaccine shortage. Increasing public confidence in vaccines and combination vaccines is also critical to fully exploit their benefits.

DTPa-HBV-IPV vaccine for primary vaccination of infants

AIM

Combined vaccines have an increasingly important role to play in delivering these antigens acceptably. We describe the immunogenicity and reactogenicity of a combined DTPa-HBV-IPV vaccine (diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus (DTPa-HBV-IPV: Infanrix penta) ) when administered for the primary vaccination of infants resulting from a study where the primary objective was to demonstrate non-inferiority of the immune response induced by DTPa-HBV-IPV using an industrial-scale IPV production process.

METHODS

Three hundred and fourteen infants received primary immunisation with DTPa-HBV-IPV at 2, 4 and 6 months of age. Routine Haemophilus influenzae immunisation was performed at 2 and 4 months of age at a separate injection site. Blood samples were taken at 2 and 7 months of age. Reactogenicity was assessed using diary cards for 7 days after each dose.

RESULTS

One month after the primary course, at least 98.9% of subjects achieved seroprotective antibody concentrations/titres against diphtheria, tetanus, hepatitis-B and polio types 1, 2 and 3. More than 97% had a vaccine response to pertussis antigens. The incidence of local injection site reactions after DTPa-HBV-IPV was similar to that for the Haemophilus influenzae vaccine site. General reactions of Grade 3 intensity were uncommon.

CONCLUSIONS

The DTPa-HBV-IPV vaccine is a new combination of vaccines previously available separately, with established effectiveness and safety profiles. Combined vaccines reduce storage requirements and minimise the number of injections required, thereby reducing distress for infants and parents. DTPa-HBV-IPV was immunogenic with an acceptable safety profile and could replace separate administration of DTPa, HBV and IPV vaccines in infants.

Immunogenicity and safety of an inactivated hepatitis A vaccine administered concomitantly with diphtheria-tetanus-acellular pertussis and haemophilus influenzae type B vaccines to children less than 2 years of age

OBJECTIVE

The availability of a hepatitis A virus vaccine for infant and early childhood immunization could reduce the transmission of hepatitis A virus in the United States. This study evaluated the immunogenicity and safety of a hepatitis A virus vaccine (Havrix, GlaxoSmithKline Biologicals, Rixensart, Belgium) administered concomitantly with diphtheria-tetanus-acellular pertussis and Haemophilus influenzae type b vaccines to children < 2 years.

METHODS

In this open, comparative, multicenter study, 1084 healthy children aged 11 to 25 months were allocated (4:4:3:3:4 ratio) to 5 treatment groups based on age and previous vaccination history. Subjects 11 to 13 months of age received 2 doses of hepatitis A virus vaccine 6 months apart (N = 243). Subjects aged 15 to 18 months received 2 doses of hepatitis A virus vaccine 6 months apart (N = 241); or hepatitis A virus vaccine, diphtheria-tetanus-acellular pertussis, and H influenzae type b at month 0 and the second dose of hepatitis A virus vaccine 6 months later (N = 183); or diphtheria-tetanus-acellular pertussis and H influenzae type b at month 0 and hepatitis A virus vaccine at months 1 and 7 (N = 175). Subjects 23 to 25 months of age received hepatitis A virus vaccine at months 0 and 6 (N = 242). Immune responses were measured at baseline and 30 days after vaccine doses, and solicited and unsolicited adverse events were collected.

RESULTS

After 2 doses of hepatitis A virus vaccine, all of the subjects in all of the groups were seropositive. Coadministration of hepatitis A virus vaccine with diphtheria-tetanus-acellular pertussis and H influenzae type b vaccines did not impact the immunogenicity of the 3 vaccines, except for the antipertussis toxoid vaccine response, which was slightly decreased. Hepatitis A virus vaccine was well tolerated in children 11 to 25 months of age.

CONCLUSION

The administration of 2 doses of hepatitis A virus vaccine on a 0- and 6-month schedule starting at 11 to 13 months of age or at 15 to 18 months of age was as immunogenic and well tolerated as the administration of 2 doses in children 2 years of age. Immune responses to diphtheria-tetanus-acellular pertussis and H influenzae type b either given alone or coadministered with hepatitis A virus vaccine were similar except for antipertussis toxoid response.

A comparison of booster immunisation with a combination DTPa-IPV vaccine or DTPa plus IPV in separate injections when co-administered with MMR, at age 4–6 years

This study evaluated GSK's combined DTPa-IPV vaccine (Infanrix-IPV) given as a fifth consecutive acellular pertussis booster dose in conjunction with the second dose of MMR vaccine (Priorix) in children aged 4-6 years. The immunogenicity and reactogenicity of this vaccine regimen was compared with separate injections of DTPa and IPV when given concomitantly with MMR. A cohort of 362 children previously primed with four doses of DTPa and OPV, and a single dose of MMR were randomized to receive either DTPa-IPV+MMR (N=181) or DTPa+IPV+MMR (N=181). Antibody concentrations were measured prior to and 1 month after the booster dose. After immunisation all subjects from both groups had seroprotective antibody levels against diphtheria, tetanus and the three poliovirus serotypes, > or = 96% showed vaccine response to PT, FHA and PRN, all were seropositive to mumps and rubella, and all but one subject were seropositive to measles. Immunogenicity results for each component antigen were similar for DTPa-IPV and separately co-administered DTPa and IPV. Local reactions were common with 24.0% and 31.1% of children experiencing swelling >50mm at the DTPa-IPV and DTPa injection sites, respectively. The DTPa-IPV combination did not increase the incidence or intensity of adverse events compared with separately administered DTPa+IPV. The response to the concomitantly administered MMR vaccine was similar in the two groups and similar to previously reported responses for a second dose of MMR. This combined DTPa-IPV vaccine has a similar reactogenicity profile to DTPa, is immunogenic when given as a booster dose at 4-6 years of age, and has no impact on the immunogenicity of a co-administered second dose of MMR vaccine.

Immunogenicity and safety of a combined DTaP–IPV vaccine compared with separate DTaP and IPV vaccines when administered as pre-school booster doses with a second dose of MMR vaccine to healthy children aged 4–6 years

Combination vaccines represent one solution to the problem of increased numbers of injections during single clinic visits. A combined DTaP-IPV (Infanrix-IPV) vaccine has been developed for use as a pre-school booster. Four hundred healthy children aged 4-6 years previously primed with 4 doses of DTaP vaccine (Infanrix), 3 doses of poliovirus vaccine and 1 dose of MMR vaccine were randomized to receive single doses of either the combined DTaP-IPV vaccine or separate DTaP and IPV vaccines in a Phase II trial (DTaP-IPV-047). All children also received a second dose of MMR vaccine. Immunogenicity was assessed in serum samples taken before and 1 month after booster administration. Safety was actively assessed for 42 days post-vaccination. Non-inferiority of the DTaP-IPV vaccine to separate DTaP and IPV vaccines was demonstrated for all DTaP antigen booster response rates and poliovirus geometric mean titers of antibody ratios. Post-vaccination, > or =99.4% of children in both groups had seroprotective levels of anti-diphtheria and anti-tetanus antibodies (> or =0.1IU/mL) and seroprotective anti-poliovirus antibody titers (> or =1:8). All children in both groups were seropositive for measles, mumps and rubella antibodies, with similar post-vaccination geometric mean concentrations/titers. No significant differences were observed in the incidence of solicited local or general symptoms, unsolicited symptoms and serious adverse events between the two groups. This combined DTaP-IPV appeared safe and immunogenic when given as a booster dose at 4-6 years of age. The DTaP-IPV vaccine had no negative effect on the response to co-administered MMR vaccine, making it well-suited for use as a pre-school booster.

Childhood and malaria vaccines combined in biodegradable microspheres produce immunity with synergistic interactions

Biodegradable microspheres may represent a potential tool for the delivery of combination vaccines. We demonstrate strong immunogenicity of five co-encapsulated antigens after a single subcutaneous inoculation in guinea pigs. Tetanus- and diphtheria-specific antibodies were not significantly affected by the presence of either antigen or by the presence of pertussis or Haemophilus influenzae type b (Hib) antigens. Microsphere formulations gave better protection against diphtheria toxin than did two injections of a licensed tetravalent vaccine. Finally, a synthetic malaria peptide antigen (PfCS) also encapsulated in PLGA microspheres increased diphtheria and tetanus-specific immunity and improved protection against diphtheria. These findings demonstrate the potential of microspheres as an alternative and promising strategy for combination vaccines with a further aptitude in reducing the number of inoculations required to gain functional immunity.

Vaccines administered simultaneously: directions for new combination vaccines based on an historical review of the literature

OBJECTIVES

The recognized benefits of administering vaccines simultaneously has encouraged vaccine producers to develop combination vaccines. If contemporary research and development can realize vaccines that achieve the current standards for safety, immunogenicity, and efficacy, other specific vaccine associations may also merit reconsideration as combination vaccines.

METHODS

An historical review of the vaccine association literature reveals two important themes: first, the programs of mass vaccination, in particular, the eradication of smallpox, sessions where multiple vaccines (other than the smallpox vaccine) were given concurrently, and the Expanded Programme on Immunization (EPI); and, second, the domain of travel vaccines, including travellers to a disease-endemic country (such as migrants, tourists, military personnel, or expatriates) and WHO requirements for international travellers.

RESULTS/CONCLUSIONS

Based on this historical review, combination vaccines worth reconsideration could fill epidemiologic niches in the EPI with, for instance, a measles--yellow fever, a measles--Japanese encephalitis or a pertussis-based paediatric combination rabies vaccine. Furthermore, other combinations could broaden protection against the pathogens responsible for meningitis, pneumonia, or enteric diseases. Nevertheless, complex issues such as necessity, feasibility, or affordability will ultimately determine if any one of these becomes a combination vaccine.

Immunization issues for the 21st century

OBJECTIVE

Review and discuss major issues of vaccination and immunization. The development and application of vaccination and immunization is one of the most remarkable successes of the 20th century. This is true both in the United States and worldwide. In the United States, a number of vaccine-preventable diseases have been all but eliminated through the development of a recommended childhood immunization schedule by governmental and nongovernmental organizations, education of providers about these recommendations, and enforcement of these recommendations by school and day care entry mandates. Despite these successes, vaccine-preventable diseases continue to occur, in part because of missed opportunities by health care providers, antivaccine forces empowered by misguided mass media, and parental ignorance. Important aspects of the 2002 recommended childhood immunization schedule are reviewed, including: birth dose hepatitis B, diphtheria underimmunization and tetanus overimmunization, increasing pertussis disease, the success of conjugate vaccines, the change in poliovirus vaccines, measles vaccine and autism, the safety of varicella vaccine, and adult vaccination recommendations. Finally, future prospects for vaccination and immunization are discussed, including: combination vaccines, vaccines against new diseases such as rotavirus, new routes of delivery of immunizing agents, the use of computerized vaccine registries to prevent missed opportunities, and vaccines against bioterrorism agents.

CONCLUSIONS

A careful analysis of risk and benefit suggests that the benefit of vaccination far outweighs the risks from the utilization of immunizing agents. Vaccination delayed may be protection denied. The bottom line is that vaccines are good and disease is bad.

Greater antibody responses to an eleven valent mixed carrier diphtheria- or tetanus-conjugated pneumococcal vaccine in Filipino than in Finnish or Israeli infants

BACKGROUND

Antibody responses to pneumococcal conjugate vaccines may vary when administered in different populations or epidemiologic settings. Understanding the causes and significance of this variation could help to determine the number of doses and timing required for protection against pneumococcal diseases in each country.

METHODS

This report compares antibody responses to aluminum-adjuvanted and nonadjuvanted mixed carrier 11-valent diphtheria- or tetanus-conjugated pneumococcal vaccine (11-PncTD) formulations when given at 6, 10 and 14 weeks and 9 months of age to Filipino infants (n = 51) and at 2, 4, 6 and 12 months of age to Finnish (n = 127) and Israeli (n = 124) infants. The study populations differ in their natural exposure to pneumococcus and risk factors for pneumococcal carriage and disease.

RESULTS

Filipino and Israeli infants had slightly but significantly higher prevaccination geometric mean concentration (GMC) of antibodies than did the Finnish infants. After three doses of aluminum-adjuvanted 11-PncTD vaccine, the Filipino infants had 1.8 to 6.7 and 1.5 to 5.0 times higher GMC than the Finnish and Israeli infants, respectively, against pneumococcal serotypes conjugated to tetanus protein. The GMC of serotypes conjugated to diphtheria toxoid was 1.3 to 3.0 and 0.7 to 2.0 times the GMC in Finnish and Israeli infants, respectively. The nonadjuvanted vaccine formulation induced generally lower GMCs.

CONCLUSIONS

The antibody responses to the tetanus-conjugated polysaccharides were considerably higher in the Filipino than in the Finnish or Israeli infants. This may be a result of several factors including the priming effect of tetanus toxoid given to pregnant women, early pneumococcal nasopharyngeal acquisition and genetic differences among populations.