Assessment of poliovirus antibody seroprevalence in high risk areas for vaccine derived poliovirus transmission in Madagascar

Abstract

BackgroundVaccine-derived polioviruses (VDPV) outbreaks typically occur in areas of low poliovirus immunity. Madagascar successfully eradicated wild poliovirus in 1997; however, multiple VDPV outbreaks have occurred since then, and numerous vaccination campaigns have been carried out to control the VDPV outbreaks. We conducted a survey of poliovirus neutralizing antibodies among Malagasy children to assess performance of vaccination campaigns and estimate the risk of future VDPV outbreaks.MethodsThis was a random community survey in children aged 6–11 months, 36–59 months and 5–14 years of age in high risk areas of Madagascar (Mahajanga, Toliara, Antsalova, and Midongy-atsimo); and in a reference area (Antananarivo). After obtaining informed consent, basic demographic and vaccination history, 2 mL of peripheral blood were collected. Neutralizing antibodies against all three poliovirus serotypes were detected by using a standard microneutralization assay.ResultsThere were 1500 children enrolled and 1496 (>99%) provided sufficient quantity of blood for analysis. Seroprevalence for poliovirus type 1 (PV1) was >90% in all age groups and study areas. PV2 seroprevalence ranged between 75–100%; it was lowest in the youngest age group in Midongy and Toliara. PV3 seroprevalence ranged between 79–100%. Seroprevalence in the reference area was not significantly different from polio high risk sites.DiscussionMadagascar achieved high population immunity. In order to preserve these gains, routine immunization needs to be strengthened. Currently, the risk of new VDPV emergences in Madagascar appears low.

Leveraging serology to titrate immunisation programme functionality for diphtheria in Madagascar

“…Consequently, the high proportion of diphtheria only seropositive individuals shown in our study either suggests high levels of circulating diphtheria, incomplete/missing vaccination or suboptimal immune response to the pertussis component of the vaccine. Selection bias may be present since only individuals with available health center registries were included excluding those not in the registries who are likely under-vaccinated [18,19]. Our analysis is also limited by the small number of districts and samples reducing the generalizability of our results.…”

“…Since the pertussis and diphtheria vaccines were combined in the mid-1940s [ 17 ], and are in use in combined form in Madagascar, interpretation of diphtheria serology titres can be strengthened by also considering serological status to pertussis. Here, we tested available Madagascar sera collected during a serology study on poliomyelitis in 2016 [ 18 ] and analysed in a pertussis serology study in 2020 [ 19 ] for anti-diphtheria IgG antibody levels to evaluate the immune profiles of children aged 6–11 months old and 8–15 years old, DTP vaccination coverage and diphtheria footprint in selected districts in Madagascar ( Fig. 1b ).…”

Seroprevalence of pertussis in Madagascar and implications for vaccination

“…The level of anti-PT IgG (IU/ml) is a marker of either pertussis infection or vaccination and is specific for B. pertussis [20][21][22]. The presence of anti-PT IgG was detected by quantitative analysis using a commercially available ELISA kit (EUROIMMUN, Lübeck, Germany).…”

“…Serum samples were collected from May to September in 2016 as part of a separate study to estimate the seroprevalence of poliovirus antibodies in high-risk areas for vaccine-derived poliovirus (VDPV) outbreaks in Madagascar [20]. Written consent was provided by participants for the use of their serum to analyse other infectious diseases.…”

“…Currently, Madagascar administers three doses of the DTCHepB + Hib vaccination (whole-cell vaccine) which follows the WHO recommended vaccination schedule at 6, 10 and 14 weeks [19]. Coverage for all three doses at the country level has been estimated to vary between 83% and 93% during the 2008–2017 period [19, 20], although heterogeneities in coverage exist at the district level. Limited reporting further complicates our understanding of pertussis epidemiology.…”