The efficacy of hepatitis B vaccination program in upper Egypt: Flow cytometry and the evaluation of long term immunogenicity

A systematic review reveals that African children of 15-17 years demonstrate low hepatitis B vaccine seroprotection rates

Childhood HBV immunization remains globally fundamental to the elimination of hepatitis B virus (HBV). However, monitoring proportions of HBV vaccine seroprotection and their determinants among African Pediatric recipients is crucial. This study sought to verify extent of immune protection accorded by the HBV vaccine in African children of up to 17 years of age by pooling the prevalence of seroprotection reported by primary studies conducted in the Northern, Western, and Southern African regions. We included 19 eligible articles out of the 197 initially downloaded, published from 1999 to 2021 from African Journals Online (AJOL), EMBASE, Scopus, and PubMed. The study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO), University of York Centre for Reviews and Dissemination, under the registration number CRD42022361277. Significantly higher (p < 0.0001) proportion of HBV vaccine seroprotection (69.07%) was found among children under 15 years of age than children 15-17 years (32.368%), 95% CI [34.2454-39.0847%]. Whereas successful integration of the HBV vaccine on the extended programs on immunizations (EPI) has been a major achievement in the reduction of HBV infection in Africa, markedly reduced HBV vaccine seroprotection is persistently demonstrated among adolescent children 15-17 years of age. Future studies are required to clarify the need for booster dose vaccination in most at risk populations and age groups.

Lower frequency of T stem cell memory (TSCM) cells in hepatitis B vaccine nonresponders

Despite the availability of an effective vaccine and antiviral treatments, hepatitis B is still a global public health problem. Hepatitis B vaccination can prevent the disease. Vaccination induces long-lasting protective immune memory, and the identification of memory cell subsets can indicate the effectiveness of vaccines. Here, we compared the frequency of CD4⁺ memory T cell subsets between responders and nonresponders to HB vaccination. Besides, the frequency of IFN-γ⁺ memory T cells was compared between studied groups. Study participants were grouped according to their anti-HBsAb titer. For restimulation of CD4⁺ memory T cells, peripheral blood mononuclear cells (PBMCs) were cultured in the presence of HBsAg and PHA for 48 h. Besides, PMA, ionomycin, and brefeldin were added during the last 5 h of incubation to induce IFN-γ production. Flow cytometry was used for analysis. There was a statistically significant difference in the frequency of CD4⁺CD95⁺, CD4⁺CD95^Hi, and CD4⁺CD95^low/med T stem cell memory (T_SCM) cells between responder and nonresponder groups. However, the comparison of the frequency of memory T cells producing IFN-γ showed no differences. Our results identified a possible defect of immunological CD4⁺ memory T cell formation in nonresponders due to their lower frequency of CD4⁺ T_SCM cells.

[Hepatitis B vaccine and liver cancer]

Hepatitis B Virus (HBV) chronic infection contributes to a high risk of hepatocellular cancer (HCC) development. HBV is a strong cancer inducer, due to natural history of infection, virological characteristics and viral DNA integrations events in host genome. Prolonged infection and high viral loads, particularly frequent in patients infected in childhood, are risk factors of HCC development for patients with HBV chronic infection. A HBV vaccine, based on immunization against the surface protein HBs, showed a strong efficacy to prevent chronic HBV infection. The development of universal neonatal vaccination programmes contributed to the decrease of HBV chronic infection incidence in children of high endemic areas. Although HBs antibodies levels diminished years after vaccination, HBV neonatal vaccination programmes led to a lower incidence of chronic HBV infection among young adults. The decrease of HBV chronic infection incidence was associated to a reduction of HCC incidence in children and young adults from areas with a high prevalence of HBV infection.

Is There Any Opportunity to Provide an HBV Vaccine Booster Dose Before Anti-Hbs Titer Vanishes?

Whether the primary Hepatitis B vaccination confers lifelong protection is debated. The aim of the study was to assess the effectiveness of booster doses in mounting a protective HBV immune response in subjects vaccinated 18-20 years earlier. The study population consisted of vaccinated students attending medical and healthcare professions schools. A booster dose was offered to subjects with a <10 mIU/mL anti-HBs titer. The post-booster anti-HBs titer was evaluated after four weeks. The subjects with a <10 mIU/mL post-booster anti-HBs titer, received a second and third dose of the vaccine and after one month they were retested. A <10 mIU/mL anti-HBs titer was found in 35.1% of the participants and 92.2% of subjects that were boosted had a ≥10 mIU/mL post-booster anti-HBs titer, whereas 7.8% did not mount an anamnestic response. A low post-booster response (10-100 mIU/mL anti-HBs) was significantly more likely in subjects with a <2.00 mIU/mL pre-booster titer compared to those with a 2.00-9.99 mIU/mL pre-booster titer. The anamnestic response was significantly related to the baseline anti-HBs levels. A booster dose of the HBV vaccine may be insufficient to induce an immunological response in subjects with undetectable anti-HBs titers. A booster dose might be implemented when an anamnestic response is still present.

Immune persistence 17 to 20 years after primary vaccination with recombination hepatitis B vaccine (CHO) and the effect of booster dose vaccination

BACKGROUND

To assess the immune persistence conferred by a Chinese hamster ovary (CHO)-derived hepatitis B vaccine (HepB) 17 to 20 years after primary immunization during early life.

METHODS

Participants born between 1997 and 1999 who received a full course of primary vaccination with HepB (CHO) and who had no experience with booster vaccination were enrolled. Blood samples were required from each participant for measurement of hepatitis B surface antibody (anti-HBs), surface antigen and core antibody levels. For those who possessed an anti-HBs antibody < 10 mIU/mL, a single dose of HepB was administered, and 30 days later, serum specimens were collected to assess the booster effects.

RESULTS

A total of 1352 participants were included in this study. Of these, 1007 (74.5%) participants could retain an anti-HBs antibody ≥10 mIU/mL, with a geometric mean concentration (GMC) of 57.4 mIU/mL. HBsAg was detected in six participants, resulting in a HBsAg carrier rate of 0.4% (6/1352). Of those participants with anti-HBs antibodies < 10 mIU/mL, after a challenge dose, 231 (93.1%) presented an anti-HBs antibody ≥10 mIU/mL, with a GMC of 368.7 mIU/mL. A significant increase in the anti-HBs positive rate (≥ 10 mIU/mL) after challenge was observed in participants with anti-HBs antibodies between 2.5 and 10 mIU/mL and participants boosted with HepB (CHO), rather than those with anti-HBs antibodies < 2.5 mIU/mL and those boosted with HepB (SC).

CONCLUSION

Since satisfactory immune protection against HBV infection conferred by primary vaccination administered 17-20 years ago was demonstrated, there is currently no urgent need for booster immunization.

Hepatitis B vaccine and the need for a booster dose after primary vaccination

OBJECTIVES

Protective antibodies levels, induced by Hepatitis B virus (HBV) vaccine, persist for long-term after primary immunization, but there is evidence that, as the time since vaccination increases, there is a reduced ability to maintain immune memory. The study aim was to determine the prevalence and the duration of persistence of an anti-HBs titer with ≥10mIU/mL and eventual predictors of reduced seroprotection.

METHODS

The study was conducted among students attending medical and healthcare professions schools from January 2014 to June 2016. Data were collected through the review of medical records completed during the medical surveillance visit. All subjects had received HBV vaccine according to the Italian Ministry of Health indications.

RESULTS

The results are reported for 722 subjects. Positive anti-HBs titer was found in 72.6% (95% CI=69-76). The mean age of the subjects was 25.5years. Subjects vaccinated during adolescence and students that had received an adult vaccine dose were significantly more likely to be seroprotected. The longer the time interval since vaccination the lower the probability of being seroprotected; however if the role of time since vaccination was considered after stratification by vaccine dose, a statistically significant association with a lower percentage of seroprotected remains only in the subgroup of subjects who received the pediatric dose. The findings of the multivariate regression analysis partially confirmed those of the univariate analysis.

CONCLUSIONS

In conclusion, our findings show that over 25% of HBV vaccine recipients had an antiHBs titer <10mIU/ml after 18years of more from the primary vaccination. Furthermore, in the case a booster dose would be needed, our results suggest that the vaccination strategy should prefer administration of a vaccine adult dose during early adolescence, since it might offer longer-term protection through adulthood.