Seroprotection at different levels of the health care system after routine vaccination with DTPw-HepB-Hib in Lao PDR.
- Vaccinology and B Cell Immunology
BACKGROUND: Lao PDR continues to sustain a considerable burden of vaccine preventable diseases because of incomplete vaccine coverage and weak vaccine responses. We have assessed seroconversion after routine vaccination with DTPw-HepB-Hib to capture weaknesses of vaccine management at the different levels of the health care system. METHODS: 1151 children (8-28 months) with three documented doses of the pentavalent vaccine delivered at Central hospitals in Vientiane and the Provincial hospital, 3 district hospitals and 10 health centers in Bolikhamxay province were enrolled. Socio-demographic information was collected with a standardized questionnaire. Serum samples were analysed for antibodies against each of the vaccine components and bivariate and multivariable analyses were performed to identify risk factors for low vaccine responses. RESULTS: Seroprotection rates at the provincial, district and health center level were as high as in Central hospitals but seroprotection rates in areas covered by remote health centers (>60 min from district hospital) were significantly lower. Protective levels also rapidly decreased with age at sampling. Seroprotection rates in Bolikhamxay against the different components reached 70%-77% and were up to 20% higher than in previous studies in the same region: 18.8% more children received the hepatitis B vaccine birth dose and the HBV infection rate was 4 times lower. CONCLUSION: Vaccine immunogenicity has dramatically improved in a central province, likely thanks to training and investment in the cold chain. Nevertheless there remains a need to focus on the "last mile" in remote areas were most children are vaccinated through outreach activities.