Impact and effectiveness of 13-valent pneumococcal conjugate vaccine on population incidence of vaccine and non-vaccine serotype invasive pneumococcal disease in Blantyre, Malawi, 2006-18: prospective observational time-series and case-control studies.

Bar-Zeev, Naor, Swarthout, Todd D, Everett, Dean B, Alaerts, Maaike, Msefula, Jacquline, Brown, Comfort, Bilima, Sithembile, Mallewa, Jane, King, Carina, von Gottberg, Anne, Verani, Jennifer R, Whitney, Cynthia G, Mwansambo, Charles, Gordon, Stephen ORCID: https://orcid.org/0000-0001-6576-1116, Cunliffe, Nigel A, French, Neil and Heyderman, Robert S (2021) 'Impact and effectiveness of 13-valent pneumococcal conjugate vaccine on population incidence of vaccine and non-vaccine serotype invasive pneumococcal disease in Blantyre, Malawi, 2006-18: prospective observational time-series and case-control studies.'. Lancet Global Health, Vol 9, Issue 7, e989-e998.

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Abstract

BACKGROUND
The population impact of pneumococcal conjugate vaccines (PCVs) depends on direct and indirect protection. Following Malawi's introduction of the 13-valent PCV (PCV13) in 2011, we examined its impact on vaccine and non-vaccine serotype invasive pneumococcal disease among vaccine-eligible-age and vaccine-ineligible-age children and adults.

METHODS
We did a prospective observational time-series analysis and a case-control study. We used data from between Jan 1, 2006, and Dec 31, 2018, from laboratory-based surveillance at a government hospital in Malawi. This period included 6 years before and 7 years after introduction of PCV13. By use of negative-binomial regression, we evaluated secular trend-adjusted incidence rate ratio (IRR) in vaccine serotype and non-vaccine serotype invasive pneumococcal disease before and after introduction of PCV. We compared predicted counterfactual incidence in hypothetical absence of vaccine with empirically observed incidence following vaccine introduction. The case-control study assessed vaccine effectiveness, comparing PCV uptake among cases of vaccine-eligible-age invasive pneumococcal disease versus matched community controls.

FINDINGS
Surveillance covered 10 281 476 person-years of observation, with 140 498 blood and 63 291 cerebrospinal fluid cultures. A reduction in total (vaccine serotype plus non-vaccine serotype) invasive pneumococcal disease incidence preceded introduction of PCV: 19% (IRR 0·81, 95% CI 0·74 to 0·88, p<0·0001) among infants (<1 year old), 14% (0·86, 0·80 to 0·93, p<0·0001) among children aged 1-4 years, and 8% (0·92, 0·83 to 1·01, p=0·084) among adolescents and adults (≥15 years old). Among children aged 5-14 years there was a 2% increase in total invasive pneumococcal disease (1·02, 0·93 to 1·11, p=0·72). Compared with the counterfactually predicted incidence, incidence of post-PCV13 vaccine serotype invasive pneumococcal disease was 74% (95% CI 70 to 78) lower among children aged 1-4 years and 79% (76 to 83) lower among children aged 5-14 years, but only 38% (37 to 40) lower among infants and 47% (44 to 51) lower among adolescents and adults. Although non-vaccine serotype invasive pneumococcal disease has increased in incidence since 2015, observed incidence remains low. The case-control study (19 cases and 76 controls) showed vaccine effectiveness against vaccine serotype invasive pneumococcal disease of 80·7% (-73·7 to 97·9).

INTERPRETATION
In a high-mortality, high-HIV-prevalence setting in Africa, there were significant pre-vaccine reductions in the incidence of invasive pneumococcal disease. 7 years after PCV introduction, although vaccine-attributable impact among vaccine-eligible-age children was significant, indirect effects benefitting unvaccinated infants and adults were not. Policy decisions should consider multiple alternative strategies for reducing disease burden, including targeted vaccination outside infant Expanded Programme of Immunization to benefit vulnerable populations.

FUNDING
Bill & Melinda Gates Foundation, Wellcome Trust, and National Institute for Health Research.

Item Type:	Article
Subjects:	QS Anatomy > QS 4 General works. Classify here works on regional anatomy QW Microbiology and Immunology > Immunotherapy and Hypersensitivity > QW 806 Vaccination WA Public Health > Preventive Medicine > WA 115 Immunization WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries WC Communicable Diseases > Infection. Bacterial Infections > Bacterial Infections > WC 217 Pneumococcal infections
Faculty: Department:	Clinical Sciences & International Health > Malawi-Liverpool-Wellcome Programme (MLW)
Digital Object Identifer (DOI):	https://doi.org/10.1016/S2214-109X(21)00165-0
Depositing User:	Julie Franco
Date Deposited:	08 Sep 2021 12:09
Last Modified:	08 Sep 2021 12:09
URI:	https://archive.lstmed.ac.uk/id/eprint/18860

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