Seroprotection at Different Levels of the Healthcare System After Routine Vaccination With Diphtheria-Tetanus-Pertussis whole cell–Hepatitis B–Haemophilus influenzae Type B in Lao People’s Democratic Republic

Abstract

BackgroundThe Lao People’s Democratic Republic 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 the pentavalent vaccine to capture weaknesses of vaccine management at the different levels of the healthcare system.MethodsA total of 1151 children (aged 8–28 months) with 3 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. Sociodemographic information was collected with a standardized questionnaire. Serum samples were analyzed for antibodies against vaccine components, and bivariate and multivariable analyses were performed to identify risk factors for low vaccine responses.ResultsSeroprotection 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 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 hepatitis B virus infection rate was 4 times lower.ConclusionsVaccine immunogenicity has dramatically improved in a central province, likely due 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.

Iron Deficiency Anemia at Time of Vaccination Predicts Decreased Vaccine Response and Iron Supplementation at Time of Vaccination Increases Humoral Vaccine Response: A Birth Cohort Study and a Randomized Trial Follow-Up Study in Kenyan Infants

“…Vitamin A deficiency was defined as RBP <0.7 μmol/L at 24 wk ( 14 ). We defined immunological response as protective when participants had anti-diphtheria serum IgG concentrations ≥0.1 IU/ml ( 21 ), anti-tetanus IgG >0.5 IU/ml ( 22 ), anti-Hib IgG >1.0 μg/ml ( 22 ), anti-PnPs IgG ≥0.35 μg/ml ( 23 ), anti-measles IgG ≥0.12 IU/ml ( 24 ) and anti-OPV IgG ≥0.6, ≥2.1 and ≥0.7 IU/ml for S1, 2, and 3 ( 25 ). There is no protective serum concentration established for anti-pertussis IgG ( 22 ).…”

“…We defined immunological response as protective when participants had anti-diphtheria serum IgG concentrations ≥0.1 IU/ml ( 21 ), anti-tetanus IgG >0.5 IU/ml ( 22 ), anti-Hib IgG >1.0 μg/ml ( 22 ), anti-PnPs IgG ≥0.35 μg/ml ( 23 ), anti-measles IgG ≥0.12 IU/ml ( 24 ) and anti-OPV IgG ≥0.6, ≥2.1 and ≥0.7 IU/ml for S1, 2, and 3 ( 25 ). There is no protective serum concentration established for anti-pertussis IgG ( 22 ). We converted infant anthropometric measurements to age-adjusted z-scores in Anthro software; children with a length/height-for-age z-score < -2 were categorized as stunted; those with a weight-for-age z-score < -2 as underweight and those with a weight-for-height z-score < -2 as wasted.…”

Timeliness of immunisation with the pentavalent vaccine at different levels of the health care system in the Lao People’s Democratic Republic: A cross-sectional study

“…If children miss one visit, they may have to wait for the next visit of the health care workers. In our previous study [ 20 ] in this cohort, the place of vaccination was an important predictor for seroprotection. The proportion of protected children was especially low in villages connected to health centers that were located more than one hour of travel time from their district hospital.…”

“…The study took place in the context of a larger vaccine immunogenicity study in Bolikhamxay province and in Vientiane capital in 2017/18 (see S1 File ) [ 20 ]. All participants had received the full course of the pentavalent vaccine, documented in either the hospital records or vaccination card.…”

“…The serum samples were analysed by commercial ELISA kits as described elsewhere [ 20 ]. Protective immunity was considered if the participants had an anti-diphtheria titer ≥0.1 IU/ml, an anti-tetanus titer >0.5 IU/ml, an anti-hepatitis B titer >10 IU/L and an anti- Haemophilus influenzae type b (Hib) titer >1.0μg/ml.…”