Protective immunity against hepatitis B virus infection in a group of vaccinated Sri Lankan military service men following a complete course of vaccination.

Vaccination is the appropriate measure to protect military personnel against the hepatitis B virus (HBV) infection. Testing the military personnel for anti-HBs levels after vaccination is vital in re-vaccinating those that have not developed protective immunity. The aim of the current study was to determine the immunity in a group of vaccinated Sri Lankan military personnel (n = 150; age = 26-44 years) following a complete course of hepatitis B virus surface antigen (HBsAg) vaccination by assessing the antibodies against HBsAg (anti-HBs) levels. Three months after the last dose of the vaccination, blood samples were collected from the study population and tested for anti-HBs levels using a commercially available ELISA. Of the 150 military service men tested, 139 (92.67%) had anti-HBs levels higher than 10 mIU/mL, WHO approved levels for protective immunity against HBV infection. Of the 139 that had sufficient anti-HBs levels, 24% (36/150) had anti-HBs levels between 10 and 100 mIU/mL and 68.67% (103/150) had anti-HBs levels > 100 mIU/mL. Overall, 7.33% (11/150) participants had anti-HBs levels < 10 mIU/mL. Sero-conversion to > 10 mIU/mL anti-HBs was more than 90% in those that were less than 40 years of age and it was less than 90% in those that were more than 40 years of age.

Epidemiology and factors influencing varicella infections in tropical countries including Sri Lanka.

Varicella zoster virus (VZV) infections occur worldwide but the epidemiology differs between different geographical regions. Epidemiology of varicella is partly understood in tropical and subtropical regions. Various hypotheses showing differences in exposure rates in different age groups have been proposed. Exposure to VZV during late childhood or adolescent stage causes high morbidity, especially in high school children, university students and young work force in tropical nations. Exposure to VZV infection or sero-prevalence rates through anti-VZV immunoglobulin G appears to be lower in Sri Lanka, similar to other tropical countries prior to the millennium. In contrast, a more recent study in a group of antenatal women showed a relatively higher exposure rate to VZV when compared to the exposure rates prior to 2004 in Sri Lanka. Climatic factors, socioeconomic conditions, mobility and cultural practices appear to play a role in the differences in the exposure rates to VZV infection in the tropics. In most tropical Asian countries including Sri Lanka, routine vaccination against varicella is not carried out. Individuals with negative history for varicella take the vaccine when there is a necessity. Medical and nursing students take the vaccine prior to their clinical training to avoid adulthood varicella.