Objective: To evaluate immunogenicity and tolerability of single dose live attenuated injectable hepatitis A vaccine in four metropolitan cities of India.

Methods: Live attenuated hepatitis A vaccine was administered to 505 children aged 18 - 60 months in four centers across India. Immunogenicity of the vaccine was assessed by estimation of anti-HAV antibody titer at 6 weeks and 6 months following administration of the vaccine. Safety evaluation of the vaccine was also done during the visits.

Results: At 6 weeks, 480 subjects (95%) came for the follow-up and 411 (81.4%) subjects reported at the end of 6 months. The geometric mean titer (GMT) of anti-HAV antibody of the subjects who did not have the seroprotective titer at the baseline were assessed at 6 weeks and 6 months which was 81.04 mIU/ml and 150.66 mIU/ml respectively. At 6 weeks, 95.1 % seroconverted and at the end of 6 months, 97.9% had seroconverted. Both solicited and unsolicited vaccine-induced local and systemic adverse events were insignificant at all the centers, except swelling and induration
in a few.

Conclusion: Live attenuated injectable hepatitis A vaccine was immunogenic and tolerable with minimal reactogenecity, in this study of single dose schedule. Safety profile was also satisfactory in the study population.

Percentage serconversion has been calculated by the number of subjects who did not have the seroprotective titer 

at the baseline with the number of subjects who finally attained seroprotective antibody titer (different cut-off levels)

after vaccination at 6 weeks and 6 months follow-up visit.

The variation in the HAV titer values in the subsequent visits, i.e., in the first and the second visits after the baseline visit can be best studied if the interquartile range rather than simple range or variance is taken, because the effect of extreme observations and outliers can be eliminated by this process. The values found in the first and the second visits were 54.52 (first quartile=45.48, third quartile =100.00) and 101.00 (first quartile=92.25, third quartile=193.25) respectively. The subjects included were only those who were seronegative at the baseline (<20 mIU/mL) and attained an antibody concentration of >20mIU/mL after 6 weeks and 6 months. The age-wise seroconversion at 6 weeks and 6 months following single dose administration of live attenuated hepatitis A vaccine is shown in Table III. There were two non-responders in Mumbai and one in Kolkata, whose antibody concentration did not rise following vaccination.

TABLE III



Age-wise Seroconversion* at 6 Weeks following Single Dose Administration of 

Live Attenuated Hepatitis A Vaccine

n1 = number of cases at first follow up at 6 weeks. n2 = number of cases at second follow visit

*Seroconversion: subjects who did not have the seroprotective titer at baseline prior to vaccination and attained 

seroprotective titer after vaccination at 6 weeks and 6 months

There was no significant change in serum bilirubin and ALT values at baseline and after 6 weeks. In 1.8% cases, there was marginal rise of the enzyme which clinically was not significant as neither there was rise in the bilirubin level nor any suggested history of clinical jaundice. In the 6 weeks follow-up visit, 1.2% of the cases had raised alanine aminotransferase level but the bilirubin level was normal in all of them and none had any history of clinical hepatitis. Rest of the hematological reports was within normal limits both at the baseline and after 6 weeks of the vaccination.

Both solicited and unsolicited vaccine-induced local and systemic adverse events were insignificant at all the centers, except mild swelling and slight induration in a few children. The incidence of solicited adverse events varied from 0.20 to 1.85% and the unsolicited adverse events ranged from 0.20 to 0.82%. One subject from Kolkata centre developed systemic panniculitis which was not related to the vaccine as per the opinion of the dermatologist, and it subsequently subsided and the patient came for the follow-up visit at 6 months. There were no withdrawals from any centre on account of adverse events.

The study revealed that the administration of the live attenuated hepatitis A vaccine was found to be highly immunogenic with good tolerability and minimal reactogenecity in children 18 to 60 months of age.

The seroconversion ranged from 95% to 98% at 6 weeks and 98% to 99% at 6 months considering the different cut-off levels of seroprotective antibody titers. The geometric mean titer (GMT) of anti-HAV antibody of the subjects who did not have the seroprotective titer at the baseline were assessed at 6 weeks and 6 months, which was 81.04 mIU/mL (95% CI–70.67-92.85 ) and 150.66 mIU/mL ( 95% CI–127.23–162.88), respectively following the vaccination when >20mIU/mL was considered as the seroprotective titer.

The variation in the HAV titers in the interquartile analysis revealed that the variation increased as the time gap increased. The increasing anti-HAV antibody titers at 6 months following single dose of the vaccine might be due to the fact that this vaccine contained whole structure of the attenuated H2 strain virus particle that induced immune responses similar to the natural infection in humans. Besides this, the increase in seroconversion could be due to natural infection also. It has been reported that this vaccine can induce not only neutralizing antibodies but also the cell-mediated immune responses. As a result, the protection based on cellular immunity could persist even after anti-HAV antibodies become undetectable. When vaccinees are re-exposed to HAV, an anamnestic response may well prevent overt disease(12).

While analysing the age-wise seroconversion at 6 weeks and 6 months following single dose administration of the vaccine, the GMT at 6 weeks and 6 months were maximum in the age group 18-24 months. Thus the vaccine is highly immunogenic at an early age. In other groups, most of the subjects achieved seroprotective level at 6 months following single dose of the vaccine. More than 95% children who did not report at 6 months had seroconverted at 6 weeks. The observations show that inclusion of this group would not have changed the data significantly with the inclusion in the final analysis.

In this study, 3 subjects were nonresponders, which may be due to a lowered immunity in general or because the host’s immune system did not have a B-cell capable of generating antibodies against that antigen. In a multivariate analysis, it has been seen that the CD4 count at the time of vaccination was associated with the absence in the response to hepatitis A vaccine (P<0.0001)(13). In our study, these subjects could not be followed up for the CD4 count.

We did not find serious vaccine related adverse reaction in any subject over a period of 6 months after administration of the vaccine. Excepting in few cases, subjects developed mild swelling, pain and erythema. None of the child developed clinical or biochemical hepatitis following vaccination. Although we observed the safety profile in the subjects, this study was not adequately powered statistically to comment on the safety of the vaccine as the primary outcome.

The only Indian study(7) on this vaccine has shown its high immunogenicity and excellent safety profile that is further strengthened by the present study. Studies from China also showed high immunogenicity of the vaccine and the long term studies showed persistence of protective antibody level up to 15 years following a single dose of live attenuated HA vaccine. A comparative study with single and booster dose did not reveal any significant advantage in the long term protective value with the addition of booster(12,14-16). Further studies to evaluate the long term persistence of anti-HAV antibody after the single dose of live attenuated hepatitis A vaccine in children of India, are needed.

It can be concluded that this live attenuated hepatitis A vaccine is tolerable with minimal reactogenecity and it is immunogenic in children 18 months to 5 years of age with the single dose.

Acknowledgment is made to Dr A Parthasarathy (former IAPCOI Chairperson), Dr Apurba Ghosh (Director, ICH Kolkata), Dr MKC Nair (Past IAP President) for their advise in the study project. Professor M Pal and Dr P Bharati of Indian Statistical Institute, Kolkata for their assistance in carrying out the statistical analysis of the study.

Contributions: SC, MMA, NS, TKG, VSS and MM were responsible for designing the study. MM was primarily responsible for day to day conduct of the study. VA, JC, MMA, TKG, AA, SC, NGB and MM drafted the paper. MM will act as the guarantor for the manuscript.

Funding: Study was conducted with funding from Wockhardt India Ltd., Mumbai.

Competing interests: None stated.

1. Jindal M, Rana SS, Gupta RK, Das K, Kar P. Serological study of hepatitis A virus infection amongst the students of a medical college in Delhi and evaluation of the need of vaccination. Indian J Med Res 2002; 115: 1-4.

2. Joshi N, Yr NK, Kumar A. Age related seroprevalence of antibodies to hepatitis A virus in Hyderabad, India. Trop Gastroenterol 2000; 1: 63-65.

3. Arankalle VA, Tsarev SA, Chadha MS, Alling DW, Emerson SU, Banerjee K, et al. Age-specific prevalence of antibodies to hepatitis A and E viruses in Pune, India, 1982 and 1992. J Infect Dis 1995; 171: 447-450.

4. Arankalle VA, Chadha MS, Chitambar SD, Walimbe AM, Chobe LP, Gandhe SS. Changing epidemiology of hepatitis A and hepatitis E in urban and rural India (1982-1998). J Viral Hepat 2001; 8: 293-303.

5. Indian Academy of Pediatrics Committee on Immunization. Hepatitis A vaccine. In: Shah RC, Shah NK, Kukreja S, eds. Guidebook on Immunization. Mumbai: Indian Academy of Pediatrics 2006: 32-33,79.

6. WHO. Hepatitis A vaccines, Position paper. Wkly Epidemiol Rec 2000; 75:38-42.

7. Bhave S, Bavdekar A, Madan Z, Jha R, Bhure S, Chaudhari J, et al. Evaluation of immunogenicity and tolerability of a live attenuated hepatitis a vaccine in Indian children. Indian Pediatr 2006; 43: 983-987.

8. Lemon SM. Type A viral hepatitis: Epidemiology, diagnosis and prevention. Clin Chem 1997; 43:1494-1499.

9. Ambrosch F, Widermann G, Andre FE. Comparison of HAV antibodies induced by vaccination, passive immunization and natural infection. In: Hollinger FB, Lemon SM, Margolis HS, eds. Viral Hepatitis and Other Liver Disease. Baltimore: Williams and Wilkins; 1991. p. 98-100.

10. Berger R, Just M, Beat A. Time course of hepatitis A/antibody production after active, passive and active/passive immunization: the results are highly dependent on the antibody test system used. J Vir Meth 1999; 13: 287-298.

11. Nolan T, Bernstein H, Blatter MM., Bromberg K, Gueria F, Kennedy W, et al. 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. Pediatrics 2006;118: e602- 609.

12. Wang XY, Xu ZY, Ma JC, Von Seidlein L, Zhang Y, Hao ZY, et al. Long-term immunogenecity after single and booster dose of a live attenuated hepatitis A: Results from 8-year follow-up. Vaccine 2007; 25 : 446-449.

13. Rimland D, Guest JL. Response to hepatitis A vaccine in HIV patients in the HAART era. AIDS 2005; 19: 1702-1704.

14. Zhuang F, Qian W, Mao ZA, Gong YP, Jiang Q, Jiang LM, et al. Persistent efficacy of live attenuated hepatitis A vaccine (H2 strain) after a mass vaccination program. Chin Med J 2005; 118: 1851-1856.

15. Xu Z, Wang X, Li R, Meng Z, Zhang Y,Gong J, et al. Immunogenecity and efficacy of two live attenuated hepatitis vaccines (H2 strain and LA-1strains) Zhonghua Yi Xue Za Zhi 2002; 82: 678-681.