Seroprevalence of Hepatitis B among recipients of the WHO- EPI vaccine 10 years after the integration of the Heptitis B vaccine in to the EPI of Wa Municipality, Ghana.

Hepatitis B is a serious infectious disease of the liver and a major public health problem worldwide. It is however vaccine preventable as evidenced in the developed world. As per the WHO recommendations, Ghana and specifically, the Wa Municipal Health Administration included the hepatitis B vaccine ( HB) in the national Expanded Programme of Immunization (EPI) in 2002. This study evaluated the sero prevalence of hepatitis B virus, anti- HBs levels and sero protection rates among children in the Wa Municipality 5 to 10 years after completing their primary HBV vaccination schedule as part of the EPITwo hundred and thirty three symptomatically healthy pupils who had received the hepatitis B vaccine as part of their primary infant immunization were followed up 5 to 10 years after their primary immunization schedule against the background of 234 pupils who were born before the integration of the HBV vaccine in to the EPI and so never received the HBV vaccine as part of the EPI. Blood samples were taken and tested for HBsAg, HBsAb, HBeAg, HBeAb and HBcAb at the Upper West Regional Hospital laboratory. The samples from the children who had received the hepatitis B vaccine as part of their infant immunization were further tested quantitatively to determine the anti- HBs antibody levels by enzyme- linked immunosorbent assay (ELISA) at the Navrongo Institute of Tropical Research. Participants with anti HBs antibody titres greater than or equals to 10 mIU/mL considered seroprotected as per WHO and Kit manufacturer’s standards.Prevalence of HBV measured by HBsAg positivity among the children decreased from 10.3 % among children who had not been vaccinated to 0.9% among the vaccinated children. The significant decrease in the prevalence of HBV among the two groups of participants could be attributed to the effectiveness of the pentavalent vaccine in preventing the transmission of HBV among the vaccinated children. The overall prevalence among the children in the Wa Municipality is 5.57 % based on HBsAg positivity. After vaccination one was less likely to be associated with HBV and more likely to test positive for anti HBs. Anti-HBs titres recorded ranged from 0.0mIU/mL to 462.7 mIU/mL. Only one participant recorded an anti- HBs level of 0mIU/mL indicating a 99.57% seroconversion rate. The protective immunity measured by anti – HBs levels greater than or equal to 10 mIU/mL is 27.04% among the vaccinated children. No significant difference was observed in the anti HBs antibody levels between the male and female vaccinated children. (p: 0.458). But it was evident that the anti HBs levels though extremely low, increased with increasing age for children between 6 years and 8years. This was supported by increasing GMT levels from 36.6mIU/mL in children between the ages of 5 to 7 years with a mean age 6.7 years to 48.4 mIU/mL in children between the ages of 8 to 10 years with a mean age of (8.4). (P < 0.0001).This was observed after an initial decrease in anti HBs levels with increasing age for children between the ages of 5 and 6 years and also in children between the ages of 8 to 10 years. This finding might be as a result of the fact that the vaccinated children with anti HBs levels below the protective range probably responded to the primary vaccination but the anti HBs levels have waned over the years to levels that are considered non protective. They might have xv developed an immune memory that recognizes and produces anti- HBs upon exposure to the hepatitis B virus. (Anamnestic Response). This might be the reason why older vaccinated 7 and 8 year old children who completed the primary infant vaccination much earlier rather recorded higher anti HBs levels than children between the ages of 5 and 6 years who received their vaccination much later. Two (0.9%) vaccinated children demonstrated break through infections compared to 10.3% among the non vaccinated group suggesting the pentavalent vaccine within the frame work of the EPI is effective in protecting majority of the children in high endemic areas from HBV infection. It can be concluded that the penta valent vaccine given at 6, 10 and 14 weeks as part of the EPI for infants, is highly effective as it has shown a positive impact in the elimination of the HBV in children under 10 years of age.

Source: KNUST