The Impact of a Revised National Childhood Immunization Schedule on Vaccination Defaulters

Immunization schedules affect community vaccine uptake rates, especially in children who have defaulted on their regular immunization timelines. In 2020, Singapore revised its National Childhood Immunization Schedule (NCIS) to incorporate two new combination vaccines: the hexavalent hepatitis, diphtheria, acellular pertussis, tetanus (DTaP), hemophilus influenzae b (Hib), inactivated poliovirus (IPV) (6-in-1), and the quadrivalent measles, mumps, rubella, and varicella (MMRV) vaccines, thus reducing the mean number of clinic visits and vaccine doses by two. Our database study aims to evaluate the impact of the 2020 NCIS on catch-up vaccination uptake rates in children at 18 and 24 months of age and the catch-up immunization rates of individual vaccines at two years. Vaccination data from two cohorts, in 2018 (n = 11,371) and in 2019 (n = 11,719), were extracted from the Electronic Medical Records. Catch-up vaccination rates increased by 5.2% and 2.6% in children on the new NCIS at 18 and 24 months, respectively. The uptake of individual 5-in-1 (DTaP, IPV, Hib), MMR, and pneumococcal vaccines increased by 3.7%, 4.1%, and 1.9% at 18 months. Reduced vaccination doses and visits in the new NCIS bring direct and indirect benefits to parents and promote vaccination adherence for their children. These findings highlight the importance of timelines in improving catch-up vaccination rates in any NCIS.

Current and next-generation formulation strategies for inactivated polio vaccines to lower costs, increase coverage, and facilitate polio eradication

Implementation of inactivated polio vaccines (IPV) containing Sabin strains (sIPV) will further enable global polio eradication efforts by improving vaccine safety during use and containment during manufacturing. Moreover, sIPV-containing vaccines will lower costs and expand production capacity to facilitate more widespread use in low- and middle-income countries (LMICs). This review focuses on the role of vaccine formulation in these efforts including traditional Salk IPV vaccines and new sIPV-containing dosage forms. The physicochemical properties and stability profiles of poliovirus antigens are described. Formulation approaches to lower costs include developing multidose and combination vaccine formats as well as improving storage stability. Formulation strategies for dose-sparing and enhanced mucosal immunity include employing adjuvants (e.g. aluminum-salt and newer adjuvants) and/or novel delivery systems (e.g. ID administration with microneedle patches). The potential for applying these low-cost formulation development strategies to other vaccines to further improve vaccine access and coverage in LMICs is also discussed.

The Challenges and Opportunities of Next-Generation Rotavirus Vaccines: Summary of an Expert Meeting with Vaccine Developers

The 2nd Next Generation Rotavirus Vaccine Developers Meeting, sponsored by PATH and the Bill and Melinda Gates Foundation, was held in London, UK (7-8 June 2022), and attended by vaccine developers and researchers to discuss advancements in the development of next-generation rotavirus vaccines and to consider issues surrounding vaccine acceptability, introduction, and uptake. Presentations included updates on rotavirus disease burden, the impact of currently licensed oral vaccines, various platforms and approaches for next generation rotavirus vaccines, strategies for combination pediatric vaccines, and the value proposition for novel parenteral rotavirus vaccines. This report summarizes the information shared at the convening and poses various topics worthy of further exploration.

Physician preferences for attributes of pediatric combination vaccines in the United States

OBJECTIVE

To understand physician preferences for various attributes of pediatric combination vaccines.

METHODS

An online survey was completed by 400 US physicians (pediatricians and family physicians) who routinely administer vaccines to infants aged 1-12 months in outpatient settings. Respondents completed a discrete choice experiment (DCE) by selecting their preferred options from different hypothetical vaccine profiles with systematic variation in the levels of five attributes: vaccine presentation, number of injections administered at a single visit, completion rates, timeliness rates (within 30 days of recommended age), and years of availability for routine use, assuming similar cost, safety, and efficacy. Odds ratios and relative attribute importance scores were estimated using a random parameters logit model.

RESULTS

Physicians (mean age 50.4 years, 52.5% women) preferred combination vaccines that reduced the number of injections administered at a single visit, facilitated higher completion and timeliness rates for the primary DTaP series, were available as a pre-filled syringe rather than a vial needing reconstitution and had been available for routine use for more than 1 year. All odds ratios were statistically significant. Physicians were twice as likely to prefer administering three injections in a single visit instead of four. The most important attribute was the number of injections administered at a single visit (relative importance 38%), followed by timeliness, completion rates, and vaccine presentation; years a vaccine has been available was the least important attribute.

CONCLUSION

US physicians prefer pediatric combination vaccines that enable fewer injections to be administered at a single visit, facilitate higher completion and timeliness rates, are offered as a pre-filled syringe, and have been available for routine use for more than 1 year. The most important attribute of pediatric combination vaccines was a reduction in the number of injections administered at a single visit.

Timing of Monovalent Vaccine Administration in Infants Receiving DTaP-based Combination Vaccines in the United States

BACKGROUND

The recommended US infant immunization schedule includes doses of diphtheria, tetanus, acellular pertussis (DTaP), inactivated poliovirus (IPV), Haemophilus influenzae type b (Hib) and hepatitis B virus (HepB) during the first 6 months of life. Little information is available about the timing of associated, complementary monovalent vaccine administration in infants receiving DTaP-based pentavalent combination vaccines.

METHODS

This was a retrospective cohort study of infants born between July 1, 2010, and June 30, 2018, in the US MarketScan commercial claims and encounters database. Descriptive statistics were used to assess vaccine administration patterns. Multivariate logistic regression was performed to explore factors associated with coadministration of DTaP-IPV/Hib and HepB.

RESULTS

Among infants who received DTaP-HepB-IPV (n = 129,885), 93.7% had claims for at least 2 Hib doses; most (91.5%-98.3%) of these doses were administered on the same day as DTaP-HepB-IPV doses. Among infants who received DTaP-IPV/Hib (n=214,172), 95.3% had claims for ≥2 doses of HepB. Although coverage was high, 59.2% received the second HepB dose on the same day as the first DTaP-IPV/Hib dose, and 44.6% received the third dose of HepB on the same day as the third DTaP-IPV/Hib dose. Differences in coadministration of the second and third HepB doses with DTaP-IPV/Hib were associated with the region of residence, provider type, health plan type and coadministration of pneumococcal conjugate vaccine and rotavirus vaccine.

CONCLUSIONS

Almost all infants received the appropriate, complementary monovalent vaccine series. However, this study found variability in the timing of HepB doses in relation to DTaP-IPV/Hib doses with many infants not completing the HepB series until 9 months of age.

Control of vaccine preventable diseases in Australian infants: reviewing a decade of experience with DTPa-HBV-IPV/Hib vaccine

The combined vaccine against diphtheria, tetanus, pertussis, hepatitis B, poliomyelitis, and Haemophilus influenzae b (DTPa-HBV-IPV/Hib, Infanrix Hexa, GSK) has been used for childhood immunization in Australia according to a two-, four-, six-month schedule since 2009. We reviewed data available in the Australian National Notifiable Diseases Surveillance System, annual vaccination coverage reports, the Database of Adverse Event Notifications, and peer-reviewed literature to assess vaccine coverage rates, incidence of all six vaccine preventable diseases, and the safety profile of DTPa-HBV-IPV/Hib vaccine in Australian infants over a period of ten years of exclusive use. Between 2009 and 2018 vaccine coverage for infants aged 12 months increased from 91.7% to 94.0% and from 84.9% to 92.6% for all and for Indigenous infants, respectively. Over the same time period, there were no reports of poliomyelitis, diphtheria or tetanus in infants <12 months of age. The incidence of hepatitis B among Australian infants <12 months of age remains 10 to 20-fold lower than the national average. Control of Haemophilus influenzae b (Hib) and pertussis disease has continued to be challenging. Timely administration of the primary series, as well as increasing coverage rates, particularly among Indigenous children, has contributed to improvements in Hib and pertussis disease control. The incorporation of additional strategies such as adjustment of the first vaccination encounter to six weeks of age, parental cocooning, and most recently maternal vaccination has further reduced the burden of pertussis, particularly during the first six months of life. The frequency of the ten most common adverse events related to the DTPa-HBV-IPV/Hib vaccine demonstrates an acceptable safety profile. Data collected over ten years of consistent, exclusive use of the DTPa-HBV-IPV/Hib vaccine in Australia highlights combination vaccination as a cornerstone in maintaining infant health.

Potential protective immunogenicity of tetanus toxoid, diphtheria toxoid and Cross Reacting Material 197 (CRM197) when used as carrier proteins in glycoconjugates

When tetanus toxoid (TT), diphtheria toxoid (DT) or Cross Reacting Material 197 (CRM197), a non-toxic diphtheria toxin mutant protein, are used as carrier proteins in glycoconjugate vaccines, these carriers induce a protein specific antibody response as measured by in vitro assays. Here, it was evaluated whether or not glycoconjugates based on TT, DT or CRM197 can induce a protective immune response as measured by potency tests according to the European Pharmacopoeia. It could be shown, that the conjugate carriers TT and DT can induce a protective immune response against a lethal challenge by toxins in animals, while glycoconjugates based on CRM197 failed to induce a protective immune response. Opportunities for new applications of glycoconjugates are discussed.

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 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.

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.

Parental and societal values for the risks and benefits of childhood combination vaccines

BACKGROUND

New combination vaccines reduce the number of injections needed for immunization. However, possible drawbacks include higher prices, extra doses of vaccine antigens and increased minor adverse events. Our objective was to measure parental and societal values for attributes of childhood combination vaccines.

METHODS

We conducted a discrete choice experiment using an online survey of adults administered by Knowledge Networks. Values were measured for attributes of combination vaccines for a hypothetical child aged 6 months: (1) number of injections, (2) extra dose of hepatitis B vaccine, (3) 20% higher chance of fever, (4) community-level immunization coverage of 2-year-olds of 90% or 80%, and (5) cost per visit. Logistic regression with generalized estimating equations was used to analyze the value of different attributes and generate a marginal willingness-to-pay for a change in attribute level.

RESULTS

The response rate was 64% (N=558). Most respondents were parents (63%) and most respondents agreed that combination vaccines were safe (77%). Respondents were willing to pay $7.68 to avoid an injection (compared to $9.94 when looking at parents only). However, respondents were willing to pay $41.57 to avoid higher risk of fever after one set of immunizations (10% versus 30%) and $65.42 for higher immunization coverage rates. These results were very similar for parents only. There was no significant preference to avoid an extra dose of hepatitis B vaccine.

CONCLUSIONS

Respondents were willing to pay larger amounts to avoid increased risk of minor adverse events and to increase community-level immunization coverage than to avoid injections. These values should be taken into account when determining the risks and benefits of combination vaccines.