Low Response to Hepatitis A Vaccine among Vaccinated Individuals in Diyala Province, Iraq

Abstract

Background: The vaccination for the hepatitis A virus (HAV) is very effective in preventing HAV infection, but some people who receive the vaccine do not develop levels of antibody to protect them. The aim of this study was to assess the prevalence of low responders to hepatitis A vaccine and to determine factors associated with poor antibody response to Hepatitis A vaccination in vaccinated children in Diyala Province, Iraq.

Methods: A cross-sectional survey was performed of 435 children aged 1–15 years who had been vaccinated against hepatitis A. The study sample consisted of participants who were included in the study from Baquba City, Diyala Province. The anti-HAV IgG antibodies present in the serum were determined by enzyme-linked immunosorbent assay (ELISA); according to the World Health Organization (WHO) criteria, the antibody level <10 mIU/mL was deemed non-protective. The descriptive statistics and the inferential analyses, such as the Chi-square test, were conducted with SPSS version 27, P value <0.05 was considered statistically significant.

Results: Of the 435 immunised children, 104 (23.9%) had levels of anti-HAV IgG antibody below the protection level. The mean antibody level was 7.12 ± 1.9 mIU/mL among the low responders. There were no statistically significant relationships between antibody response and age, sex, vaccination schedule, feeding pattern, duration since vaccination, or chronic diseases (P > 0.05).

Conclusion: About 25% of vaccinated children did not develop antibody levels that provide protection after vaccination. None of the factors that were assessed—including age, pregnancy, breastfeeding status, and vaccination history—was significantly associated with low antibody levels. These results also indicate that there is a need for serological monitoring after vaccination and further research to determine other factors linked with poor vaccine-induced immunity