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

•The adult hepatitis B chronic infection rate was high; the birth dose vaccine needs strengthening.•There was low diphtheria/tetanus protection (low vaccine coverage/waning); this warrants a booster.•There were low measles antibodies in the young; this was unexpected, given infant/supplementary vaccinations.•Vaccination in Saravan needs strengthening, particularly in infants and vulnerable groups. Lao People’s Democratic Republic has frequent outbreaks of vaccine-preventable diseases (VPD). This study 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. Patients from three district hospitals and one provincial hospital were enrolled. Serum was tested by ELISA for IgG against hepatitis B virus (HBV), tetanus, diphtheria, measles, and rubella. The study enrolled 2463 participants aged 5–90 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; 9.9% had serology compatible with vaccination. Seroprevalence of protective anti-tetanus antibodies was 46.3% overall. Protective anti-diphtheria seroprevalence was 40.5%. Anti-measles seroprevalence increased from 16.7% in those aged 5–10 years to 97.7% in those aged >50 years. Anti-rubella seroprevalence was 93.0% overall. There were differences in seroprevalences between sex, districts and ethnicity. 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.