TY - JOUR
T1 - Haemophilus influenzae serotype b seroprevalence in central Lao PDR before and after vaccine introduction
AU - Hefele, Lisa
AU - Lai, Jana
AU - Vilivong, Keoudomphone
AU - Bounkhoun, Toukta
AU - Chanthaluanglath, Valin
AU - Chanthongthip, Anisone
AU - Balloch, Anne
AU - Black, Antony P.
AU - Hübschen, Judith M.
AU - Russell, Fiona M.
AU - Muller, Claude P.
N1 - Funding: This work was supported by the Ministry of Foreign and European Affairs, Luxembourg (project “Luxembourg-Laos Partnership for Research and Capacity Building in Infectious Disease Surveillance II”), and the Luxembourg Institute of Health. Some of the fieldwork was supported by a grant from the Bill & Melinda Gates Foundation (OPP1115490). In addition, FR was supported by an NHMRC investigator grant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
PY - 2022/9/15
Y1 - 2022/9/15
N2 - INTRODUCTION: Vaccination has dramatically reduced invasive Haemophilus influenzae type b (Hib) disease worldwide. Hib vaccination was introduced in the Lao PDR in 2009, as part of the pentavalent vaccine. To contribute to the understanding of the epidemiology of Hib in Lao PDR and the protection levels before and after the introduction of the vaccination, we tested serum samples from existing cohorts of vaccine age-eligible children and unvaccinated adolescents for antibodies against Hib. METHODS: Serum samples from 296 adolescents born before vaccine introduction and from 1017 children under 5 years (vaccinated and unvaccinated) were tested for anti-Hib antibodies by ELISA. Bivariate analyses were performed to investigate factors associated with long-term protection. RESULTS: The vast majority of all participants showed evidence of short- (42.7%) or long-term (56.1%) protection against Hib. Almost all of the unvaccinated adolescents had antibody titers indicating short-term protection and almost half (45.6%) were long-term protected. Nearly all children (>99.0%) were at least short-term protected, even those that were unvaccinated or whose vaccination status was unknown. Among vaccinated children, participants vaccinated more than 1 or 2 years ago and with a mid-upper arm circumference z-score < -2 were less likely to be long-term protected. DISCUSSION: Nearly all adolescents born before the introduction of Hib vaccination in the Lao PDR had antibody titers corresponding to at least short-term protection, indicating a high burden of Hib disease at that time. After vaccine introduction, all but four children (>99%) showed at least short-term protection. Possible explanations for the proportion of protected, yet apparently unvaccinated children, may be past infections, cross-reacting antibodies or faulty vaccination documentation. Our results highlight the need for robust surveillance and reporting of invasive Hib disease to determine the burden of disease despite vaccination.
AB - INTRODUCTION: Vaccination has dramatically reduced invasive Haemophilus influenzae type b (Hib) disease worldwide. Hib vaccination was introduced in the Lao PDR in 2009, as part of the pentavalent vaccine. To contribute to the understanding of the epidemiology of Hib in Lao PDR and the protection levels before and after the introduction of the vaccination, we tested serum samples from existing cohorts of vaccine age-eligible children and unvaccinated adolescents for antibodies against Hib. METHODS: Serum samples from 296 adolescents born before vaccine introduction and from 1017 children under 5 years (vaccinated and unvaccinated) were tested for anti-Hib antibodies by ELISA. Bivariate analyses were performed to investigate factors associated with long-term protection. RESULTS: The vast majority of all participants showed evidence of short- (42.7%) or long-term (56.1%) protection against Hib. Almost all of the unvaccinated adolescents had antibody titers indicating short-term protection and almost half (45.6%) were long-term protected. Nearly all children (>99.0%) were at least short-term protected, even those that were unvaccinated or whose vaccination status was unknown. Among vaccinated children, participants vaccinated more than 1 or 2 years ago and with a mid-upper arm circumference z-score < -2 were less likely to be long-term protected. DISCUSSION: Nearly all adolescents born before the introduction of Hib vaccination in the Lao PDR had antibody titers corresponding to at least short-term protection, indicating a high burden of Hib disease at that time. After vaccine introduction, all but four children (>99%) showed at least short-term protection. Possible explanations for the proportion of protected, yet apparently unvaccinated children, may be past infections, cross-reacting antibodies or faulty vaccination documentation. Our results highlight the need for robust surveillance and reporting of invasive Hib disease to determine the burden of disease despite vaccination.
UR - http://www.scopus.com/inward/record.url?scp=85137885863&partnerID=8YFLogxK
UR - https://pubmed.ncbi.nlm.nih.gov/36107979
U2 - 10.1371/journal.pone.0274558
DO - 10.1371/journal.pone.0274558
M3 - Article
C2 - 36107979
SN - 1932-6203
VL - 17
JO - PLoS ONE
JF - PLoS ONE
IS - 9
M1 - e0274558
ER -