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High residual prevalence of vaccine-serotype Streptococcus pneumoniae carriage after introduction of a pneumococcal conjugate vaccine in Malawi: a prospective serial cross-sectional study

Swarthout, T; Fronterre, C; Lourenço, J; Obolski, U; Gori, A; Bar-Zeev, N; Everett, D; ... Heyderman, R; + view all (2019) High residual prevalence of vaccine-serotype Streptococcus pneumoniae carriage after introduction of a pneumococcal conjugate vaccine in Malawi: a prospective serial cross-sectional study. BioRxiv: Cold Spring Harbor, NY, USA. Green open access

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Abstract

Background: There are concerns that pneumococcal conjugate vaccines (PCV) in sub-Saharan Africa sub-optimally interrupt vaccine-serotype (VT) carriage and transmission, thus limiting vaccine-induced direct and indirect protection. We assessed carriage in vaccinated children and unvaccinated populations targeted for indirect protection, between 4 and 7 years after Malawi’s November 2011 introduction of PCV13 using a 3+0 schedule. / Methods: We conducted sequential prospective nasopharyngeal carriage surveys between 2015 and 2018 among healthy PCV-vaccinated and PCV-unvaccinated children, and HIV-infected adults. VT and NVT carriage risk by age was analysed by non-linear regression. / Results: Among PCV-vaccinated children, there was a 24% relative reduction in carriage, from a mean 21.1% to 16.1%; 45% reduction among older PCV-unvaccinated children, from 27.5% to 15.2%; 41.4% reduction among adults, from 15.2% to 8.9%. Using carriage data from children 3.6 to 10 years of age, VT carriage probability declined with age, with a similar prevalence half-life among PCV-vaccinated (3.34 years) and PCV-unvaccinated (3.26 years) children. / Conclusion: Compared to high-income settings, the 3+0 schedule in Malawi has led to a sub-optimal reduction in pneumococcal carriage prevalence. This is likely due to recolonisation of vaccinated children with waning vaccine-induced immunity, resulting in insufficient indirect protection of unvaccinated populations. Rigorous evaluation of strategies to augment vaccine-induced control of carriage, including alternative schedules and catch-up campaigns is required.

Type: Working / discussion paper
Title: High residual prevalence of vaccine-serotype Streptococcus pneumoniae carriage after introduction of a pneumococcal conjugate vaccine in Malawi: a prospective serial cross-sectional study
Open access status: An open access version is available from UCL Discovery
DOI: 10.1101/445999
Publisher version: https://doi.org/10.1101/445999
Language: English
Additional information: The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Infection and Immunity
URI: https://discovery.ucl.ac.uk/id/eprint/10088042
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