Age-stratified seroprevalence of vaccine-preventable infectious disease in Saravan, Southern Lao People's Democratic Republic.

BACKGROUND Lao People's Democratic Republic has frequent outbreaks of vaccine-preventable diseases (VPD). We aimed to determine susceptibility and exposure to VPD in Saravan, a rural province with high ethnic diversity and some of the poorest health indicators nationwide. METHODS Patients from 3 district hospitals and 1 provincial hospital were enrolled and their serum tested by ELISA for IgG against hepatitis B virus (HBV), tetanus, diphtheria, measles and rubella. RESULTS We enrolled 2463 participants aged 5 to 90 years. Exposure to HBV was 33.2% and increased with age up to 62.4% of those aged >50 years. HBV surface antigen prevalence was 5.7% in males and 2.4% in females but only 9.9% had serology compatible with vaccination. Seroprevalence of protective anti-tetanus antibodies was only 46.3% overall. Protective anti-diphtheria seroprevalence was only 40.5%. Anti-measles seroprevalence increased from 16.7% in 5-10 year olds to 97.7% in those >50. Anti-rubella seroprevalence was 93.0% overall. There were differences in seroprevalences between sex, districts and ethnicity. CONCLUSIONS Routine infant vaccination needs strengthening in order to close the immunity gaps. High burden of HBV infection should be addressed by increasing birth dose vaccine coverage. Regional and ethnic differences need to be investigated to enable a targeted approach to vaccination.