Comparative evaluation of a combined DTP-HB vaccine in the EPI in Chiangrai Province, Thailand

Immunogenicity of the pentavalent DTwP-HB-Hib vaccine (Shan-5) used in the Thai Expanded Program on Immunization compared to the hexavalent DTaP-HB-Hib-IPV and DTwP-HB-Hib (Quinvaxem) vaccines administered to infants at 2, 4, 6 months of age

BACKGROUND

The pentavalent DTwP-HB-Hib (Shan-5) vaccine was first introduced into the Thailand Expanded Program on Immunization (EPI) in 2019. The Shan-5 vaccine is administered to infants at 2, 4, and 6 months of age, after initial vaccination with monovalent hepatitis B (HepB) and Bacillus Calmette-Guérin (BCG) vaccines at birth. This study compared the immunogenicity of the HepB, diphtheria, tetanus, and Bordetella pertussis antigens incorporated in the EPI Shan-5 vaccine versus the optional pentavalent (DTwP-HB-Hib) Quinvaxem and hexavalent (DTaP-HB-Hib-IPV) Infanrix-hexa vaccine.

METHODS

Three-dose Shan-5-vaccinated children were prospectively enrolled at the Regional Health Promotion Centre 5, Ratchaburi province, Thailand, between May 2020 and May 2021. Blood sampling was performed at months 7 and 18. The levels of HepB surface antibody (anti-HBs), anti-diphtheria toxoid (DT) IgG, anti-tetanus toxoid (TT) IgG, and anti-pertussis toxin (PT) IgG were evaluated using commercially available enzyme-linked immunoassays.

RESULTS

Anti-HBs levels of ≥10 mIU/mL were achieved in 100 %, 99.2 %, and 99.2 % of infants in the Shan-5 EPI group, hexavalent group and Quinvaxem group one month after four dose immunization (at 0, 2, 4, 6 months of age), respectively. The geometric mean concentrations of the EPI Shan-5 and hexavalent groups were comparable but were higher than those of the Quinvaxem group. At one month after primary vaccination (month 7), infants in the Shan-5 EPI group had significantly higher levels of anti-DT IgG, anti-TT IgG, and anti-PT IgG than infants in the hexavalent and Quinvaxem groups.

CONCLUSIONS

The immunogenicity of the HepB surface antigen in the EPI Shan-5 vaccine was similar to that achieved by the hexavalent vaccine, but was higher than that achieved by the Quinvaxem vaccine. The Shan-5 vaccine is highly immunogenic and generates robust antibody responses after primary immunization.

Challenges and opportunities in developing a Shigella-containing combination vaccine for children in low- and middle-income countries: Report of an expert convening

The gram-negative bacterium Shigella is an enteric pathogen responsible for significant morbidity and mortality due primarily to severe diarrhea and dysentery, mainly among children younger than five years of age living in low- and middle-income countries (LMICs). Long considered a priority target for vaccine development, recent scientific advances have led to a number of promising Shigella vaccine candidates now entering advanced stages of clinical testing. Yet, there is no guarantee that even a highly efficacious Shigella vaccine will be recommended, prioritized, purchased, and widely adopted-especially if it requires additional doses in the immunization schedule and/or visits within the immunization program. This uncertainty is due to a variety of factors, including continuing declines in Shigella-specific and overall diarrheal disease mortality rates, the increasing complexity and cost of infant immunization programs in LMICs, and the recent availability of other high-priority vaccines. Since combining a Shigella vaccine with an existing infant vaccine would conceivably increase its attractiveness, there is a need to systematically consider the challenges determining the public health value, clinical development, manufacturing, licensure, policy recommendations, and financing for a Shigella-containing combination vaccine. The international non-governmental health organization PATH convened an independent panel of 34 subject matter experts across academic, industry, philanthropic, and global health sectors to discuss hypothetical combinations of a notional parenteral Shigella vaccine with three existing vaccines in order to begin exploring the challenges associated with their development. The resulting insights and recommendations from this meeting contribute to PATH's broader effort to evaluate the public health value of potential Shigella vaccines. They may also help guide future combination vaccine development efforts more broadly.

Towards the elimination of viral hepatitis in Thailand by the year 2030

Viral hepatitis is a global problem with mortality comparable to HIV, tuberculosis and malaria. The WHO aims to eliminate hepatitis B (HBV) and hepatitis C (HCV) by 2030. Improved socioeconomic status of developing countries such as Thailand has reduced the incidence and morbidity associated with hepatitis A. Since the beginning of hepatitis B vaccination in all Thai newborns in 1992, at least 95% of one-year-olds are currently receiving 3–4 hepatitis B doses. The second vaccination of newborns of carrier mothers at 1 month of age has contributed to an effective reduction in mother-to-child transmission. Universal vaccination, blood donation screening, and decreasing needle sharing have reduced hepatitis B infection. Under the test and treat model, cost-effective screening at the point-of-care (health center or village hospital) is recommended for adults >30 years-old. Following referral to a tertiary healthcare center for a treatment plan in developing disease management plan, its implementation by trained healthcare professionals is preferably administered at the point-of-care. Hepatitis C prevalence is also decreasing as a result of blood-borne pathogen awareness. Current hepatitis C infection is highest for adults >35 years who were born prior to 1983, with screening is recommend once in their lifetime. Treatment strategy recommendation follows that of hepatitis B. The availability of direct antiviral agents with high cure rates is expected to contribute to the reduction in hepatitis C transmission and mortality as set forth by the WHO policy. Thus, ensuring the successful planning of hepatitis elimination in Thailand requires pilot regional assessment prior to national implementation.

Comparison of hepatitis B surface antibody levels induced by the pentavalent DTwP-HB-Hib versus the hexavalent DTaP-HB-Hib-IPV vaccine, administered to infants at 2, 4, 6, and 18 months of age, following monovalent hepatitis B vaccination at birth

BACKGROUND

In Thailand, the hepatitis B (HB) vaccine is administered as a tetravalent vaccine (DTwP-HB) to all infants at 2, 4, and 6 months of age, following an initial vaccination with a monovalent HB vaccine at birth. As part of ongoing vaccine evaluation, we aimed to compare the hepatitis B immunogenicity profiles of children who had received either the pentavalent (DTwP-HB-Hib) or the hexavalent (DTaP-HB-Hib-IPV) vaccine.

METHODS

Two groups of infants, whose mothers previously received the tetanus-diphtheria-acellular pertussis vaccine (Tdap), were randomly vaccinated with either pentavalent or hexavalent vaccine at 2, 4, 6, and 18 months of age, following monovalent HB vaccine at birth. Blood samples were obtained at birth, one-month post-primary series immunization (mo 7), pre-booster (mo 18), one-month post-booster (mo 19), and six months post-booster (mo 24). The third group of infants, whose mothers did not receive Tdap, was vaccinated with DTwP-HB-Hib (EPI pentavalent group). Levels of HBsAg, anti-HBc, and anti-HBs were evaluated by means of an automated Chemiluminescent Microparticle Immunoassay.

RESULTS

Anti-HBs levels of ≥10 mIU/ml were achieved in 99.2% (hexavalent group), 99.2% (pentavalent group), and 98.5% (EPI pentavalent group) of infants, after four-dose immunization (at 0, 2, 4, 6 months of age). One month after the additional dose given at 18 months of age, anti-HBs levels of ≥10 mIU/ml were observed in 100% (hexavalent group), 99.2% (pentavalent group), and 93.8% (EPI pentavalent group) of infants. At 24 months of age, higher percentages of infants achieving anti-HBs levels ≥10 mIU/ml were found in the hexavalent group (98.3%) compared to the pentavalent group (86.5%).

CONCLUSIONS

Both vaccines were effective in inducing anti-HBs levels of ≥10 mIU/ml, and therefore either can be used as a single formula booster at 18 months of age to simplify vaccine administration under the Expanded Program on Immunization in Thailand.

Implementation of hepatitis B vaccine in high-risk young adults with waning immunity

Universal hepatitis B (HB) vaccination among Thai newborns was initiated in 1992. The first dose of the monovalent HB vaccine was given at birth, then at months 2 and 6 simultaneously with the diphtheria-tetanus-pertussis whole-cell (DTPw) vaccine. In 2008, Thailand replaced the monovalent HB vaccine at months 2 and 6 with a combined DTP-HB given at months 2, 4, and 6, with an added monovalent HB vaccine at month 1 for infants whose mothers were HBV carriers. Despite this rigorous HB vaccination schedule, vaccinated infants who are now adolescents do not possess a protective level of anti-HB surface antigen (anti-HBs) (≥10 mIU/ml). Thus, many young adults may be rendered susceptible to HB infection. Our objective was to determine how HB booster vaccination may benefit high-risk adolescents. We evaluated the serological records of a cohort of medical students (n = 291), which showed that 271 students (93.1%) possessed anti-HBs less than the accepted protective level (<10 mIU/ml) and subsequently received the HB vaccine booster prior to medical school enrollment. We then examined the anti-HB surface antibody (anti-HBs) in 216 individuals six weeks after they were immunized. We found that 61%, 88%, and 94% of individuals with pre-booster anti-HBs of <1 mIU/ml, 1-<3 mIU/ml, and 3-<10 mIU/ml achieved protective anti-HBs, respectively. Post-booster geometric mean titers were 305, 513, and 1,929 mIU/ml in these groups and correlated with pre-booster anti-HBs titers. These data suggest that medical students with known anti-HBs <1 mIU/ml will benefit from 3 doses of HB vaccine at 0, 1, and 6 months. Students with anti-HBs 1-<10 mIU/ml would benefit from an HB vaccine booster without further anti-HBs evaluation.

What criteria do decision makers in Thailand use to set priorities for vaccine introduction?

Background

There is a need to identify rational criteria and set priorities for vaccines. In Thailand, many licensed vaccines are being considering for introduction into the Expanded Program on Immunization; thus, the government has to make decisions about which vaccines should be adopted. This study aimed to set priorities for new vaccines and to facilitate decision analysis.

Methods

We used a best-worst scaling study for rank-ordering of vaccines. The candidate vaccines were determined by a set of criteria, including burden of disease, target age group, budget impact, side effect, effectiveness, severity of disease, and cost of vaccine. The criteria were identified from a literature review and by in-depth, open-ended interviews with experts. The priority-setting model was conducted among three groups of stakeholders, including policy makers, healthcare professionals and healthcare administrators. The vaccine data were mapped and then calculated for the probability of selection.

Results

From the candidate vaccines, the probability of hepatitis B vaccine being selected by all respondents (96.67 %) was ranked first. This was followed, respectively, by pneumococcal conjugate vaccine-13 (95.09 %) and Haemophilus influenzae type b vaccine (90.87 %). The three groups of stakeholders (policy makers, healthcare professionals and healthcare administrators) showed the same ranking trends. Most severe disease, high fever rate and high disease burden showed the highest coefficients for criterion levels being selected by all respondents. This result can be implied that a vaccine which can prevent most severe disease with high disease burden and has low safety has a greater chance of being selected by respondents in this study.

Conclusions

The priority setting of vaccines through a multiple-criteria approach could contribute to transparency and accountability in the decision-making process. This is a step forward in the development of an evidence-based approach that meets the need of developing country. The methodology is generalizable but its application to another country would require the criteria as relevant to that country.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-016-3382-5) contains supplementary material, which is available to authorized users.

The Success of a Universal Hepatitis B Immunization Program as Part of Thailand's EPI after 22 Years' Implementation

Hepatitis B vaccination for newborns was introduced in two provinces in 1988 as part of Thailand’s Expanded Program on Immunization (EPI), and extended to the whole country in 1992. Our previous studies showed that children and adolescents who were born after the implementation of this program had a carrier rate of less than 1%, compared with 5–6% before implementation. In 2014 we performed hepatitis B serosurveys among 5964 subjects in the different geographic regions of the country to evaluate the long-term immunogenicity and impact of universal hepatitis B vaccination in newborns as part of the 22-year EPI program, by assessing HBsAg, anti-HBc and anti-HBs seropositivity status. The number of HB virus (HBV) carriers, both children and young adults, who were born after universal HB vaccination was markedly reduced. The carrier rates among the age groups 6 months to 5 years, 5–10, 11–20, 21–30, 31–40, 41–50 and >50 years were respectively 0.1, 0.29, 0.69, 3.12, 3.78, 4.67 and 5.99%. The seropositivity rate for HBsAg in the post-EPI group was 0.6%, whereas in the pre-EPI group it was as high as 4.5% (p<0.001). HBV infection by means of detectable anti-HBc had also drastically declined in the population born after the HB vaccine was integrated into the EPI program. We estimated that the total number of HBV carriers amounted to 2.22 million, or 3.48% of the total population, most of whom are adults. The HB vaccine is the first vaccine shown to be effective in preventing the occurrence of chronic liver disease and hepatocellular carcinoma. Universal vaccination campaign will contribute to the eventual eradication of HBV-associated disease.

Unraveling the complexity of hepatitis B virus: from molecular understanding to therapeutic strategy in 50 years

Hepatitis B virus (HBV) is a well-known hepadnavirus with a double-stranded circular DNA genome. Although HBV was first described approximately 50 years ago, the precise mechanisms of HBV infection and effective therapeutic strategies remain unclear. Here, we focus on summarizing the complicated mechanisms of HBV replication and infection, as well as genomic factors and epigenetic regulation. Additionally, we discuss in vivo models of HBV, as well as diagnosis, prevention and therapeutic drugs for HBV. Together, the data in this 50-year review may provide new clues to elucidate molecular mechanisms of HBV pathogenesis and shed new light on the future HBV therapies.

Viral hepatitis: global goals for vaccination

In countries where hepatitis A is highly endemic, exposure to hepatitis A virus (HAV) is almost universal before the age of 10 years, and large-scale immunization efforts are not required. In contrast, in areas of intermediate endemicity or in transition from high to intermediate endemicity, where transmission occurs primarily from person to person in the general community (often with periodic outbreaks), control of hepatitis A may be achieved through widespread vaccination programmes. Hepatitis B virus (HBV) is one of the world's most widespread infectious agents and the cause of millions of infections each year. Between 500,000 and 700,000 people die each year from chronic infection-related cirrhosis, hepatocellular carcinoma (HCC) or from acute hepatitis B. Hepatitis B vaccine provides protection against infection and its complications including liver cirrhosis and HCC. It is therefore, the first vaccine against a cancer, the first vaccine protecting from a sexually transmitted infection, and the first vaccine against a chronic disease ever licensed. Control and significant reduction in incidence of new HBV infections as well as hepatocellular carcinoma has repeatedly been reported in countries in East Asia (i.e. Taiwan) and Africa (i.e. The Gambia). Two experimental vaccines against hepatitis E have been developed; one of them has been recently licensed but is not yet widely available. Attempts to develop a hepatitis C vaccine were so far unsuccessful.

Replacing the measles ten-dose vaccine presentation with the single-dose presentation in Thailand

Introduced to minimize open vial wastage, single-dose vaccine vials require more storage space and therefore may affect vaccine supply chains (i.e., the series of steps and processes involved in distributing vaccines from manufacturers to patients). We developed a computational model of Thailand's Trang province vaccine supply chain to analyze the effects of switching from a ten-dose measles vaccine presentation to each of the following: a single-dose measles-mumps-rubella vaccine (which Thailand is currently considering) or a single-dose measles vaccine. While the Trang province vaccine supply chain would generally have enough storage and transport capacity to accommodate the switches, the added volume could push some locations' storage and transport space utilization close to their limits. Single-dose vaccines would allow for more precise ordering and decrease open vial waste, but decrease reserves for unanticipated demand. Moreover, the added disposal and administration costs could far outweigh the costs saved from preventing open vial wastage.

The immunogenicity and safety of a reduced PRP-content DTPw-HBV/Hib vaccine when administered according to the accelerated EPI schedule

Background

Combination vaccines improve coverage, compliance and effectively introduce new antigens to mass vaccination programmes. This was a phase III, observer-blind, randomized study of GSK Biologicals diphtheria-tetanus-whole cell pertussis vaccine combined with hepatitis B and Haemophilus influenzae type b vaccines, containing a reduced amount of polyribosyl-ribitol-phosphate (PRP) and a DTPw component manufactured at a different site (DTPw-HBV/Hib_2.5 [Kft]). The primary aim of this study was to demonstrate that DTPw-HBV/Hib_2.5 [Kft] was not inferior to the licensed DTPw-HBV/Hib (Tritanrix(tm)-HepB/Hiberix(tm)) vaccine or the DTPw-HBV/Hib_2.5 vaccine, also containing a reduced amount of PRP, with respect to the immune response to the PRP antigen, when administered to healthy infants, according to the Expanded Programme for Immunization (EPI) schedule at 6, 10 and 14 weeks of age.

Methods

299 healthy infants were randomised to receive either DTPw-HBV/Hib_2.5 [Kft] DTPw-HBV/Hib_2.5 or DTPw-HBV/Hib according to the 6-10-14 week EPI schedule. Blood samples were analysed prior to the first dose of study vaccine and one month after the third vaccine dose for the analysis of immune responses. Solicited local and general symptoms such as pain, redness and swelling at the injection site and drowsiness and fever, unsolicited symptoms (defined as any additional adverse event) and serious adverse events (SAEs) were recorded up to 20 weeks of age.

Results

One month after the third vaccine dose, 100% of subjects receiving DTPw-HBV/Hib_2.5 [Kft] or DTPw-HBV/Hib and 98.8% of subjects receiving DTPw-HBV/Hib_2.5 vaccine had seroprotective levels of anti-PRP antibodies (defined as anti-PRP antibody concentration ≥0.15 μg/ml). Seroprotective antibody concentrations were attained in over 98.9% of subjects for diphtheria, tetanus and hepatitis B. The vaccine response rate to pertussis antigen was at least 97.8% in each group. Overall, the DTPw-HBV/Hib_2.5 [Kft] vaccine was well tolerated in healthy infants; no SAEs were reported in any group.

Conclusions

The DTPw-HBV/Hib_2.5 [Kft] vaccine was immunogenic and well-tolerated when administered according to the EPI schedule to Indian infants.

Trial registration

http://www.clinicaltrials.gov NCT00473668

Increased risk of developing chronic HBV infection in infants born to chronically HBV infected mothers as a result of delayed second dose of hepatitis B vaccination

This two-stage study (cross-sectional and case-control) assessed the effects of delayed second dose HB vaccination on the risk of developing chronic HBV infection in infants born to chronically HBV infected mothers. 521 infants enrolled received the first vaccination by the end of the day after birth, without HBIG. 15 of these infants were chronically HBV infected. In the case-control comparison, controlling for HBeAg in the mother, the risk of an infant becoming chronically infected was 3.74 times (95% CI=0.97-14.39) higher if the interval between the first and the second doses exceeded 10 weeks. This finding suggests it is important that immunization programs ensure timely second dose vaccination to infants born to mothers with chronic HBV infection. Nevertheless, due to the small sample size, these findings should be verified by larger studies.

What influences government adoption of vaccines in developing countries? A policy process analysis

This paper proposes a framework for examining the process by which government consideration and adoption of new vaccines takes place, with specific reference to developing country settings. The cases of early Hepatitis B vaccine adoption in Taiwan and Thailand are used to explore the relevance of explanatory factors identified in the literature as well as the need to go beyond a variable-centric focus by highlighting the role of policy context and process in determining the pace and extent of adoption. The cases suggest the feasibility and importance of modeling 'causal diversity'-the complex set of necessary and sufficient conditions leading to particular decisional outcomes-in a broad range of country contexts. A better understanding of the lenses through which government decision-makers filter information, and of the arenas in which critical decisions are shaped and taken, may assist both analysts (in predicting institutionalization of new vaccines) and advocates (in crafting targeted strategies to accelerate their diffusion).