Pneumococcal carriage in households in Karonga District, Malawi, before and after introduction of 13-valent pneumococcal conjugate vaccination

Abstract

HighlightsPneumococcal carriage of any serotype remained high three years post vaccine introduction.Early acquisition of pneumococcal carriage in infants continued post vaccine introduction.Vaccine-type carriage was lower in vaccinated and unvaccinated individuals.Non-vaccine-type carriage was higher post vaccine introduction in vaccinated children.There is evidence of herd protection and serotype replacement in this population.

Determinants of high residual post-PCV13 pneumococcal vaccine type carriage in Blantyre, Malawi: a modelling study

“…The dynamic model helped explain these age-related responses, by showing that age-groups have experienced periods of higher vaccine impact at different time points, sequentially, from younger to older groups. A major implication is that reduction in VT carriage in vaccinated younger age-groups has been fastest between PCV13 introduction and 2015, when no carriage data was collected in Blantyre, but consistent with data collected in rural northern Malawi 19 . Thus, similarly to the conclusions of another modelling study 28 , our results advocate for the essential role of dynamic models to understand post-PCV13 VT carriage, by critically accounting for local nonlinear effects of pneumococcal transmission and vaccination which may have significant implications for data interpretation.…”

“…Critical for low and middle income countries, as well as global initiatives such as Gavi, is that the impact of PCVs on pneumococcal VT carriage needs to be further improved if we are to maximize disease reduction. For high burden countries like Malawi, in which post-PCV VT carriage data suggests that local epidemiological factors may dictate lower vaccine impact than elsewhere, region-specific improved vaccination schedules 19,22 and catch-up campaigns 28 could help speed-up VT carriage reduction and maximise cost-effectiveness. For this to be possible, we need to better understand local transmission profiles across ages, which are likely dictated by demographic and socio-economic factors, and strongly determine short-and long-term PCV impact.…”

“…in Sub-Saharan African countries, such as Kenya 17,18 , Malawi 19 , The Gambia 20 and South Africa 21 . In November 2011, Malawi introduced the 13-valent pneumococcal conjugate vaccine (PCV13) as part of the national extended program of immunization with a 3+0 schedule (at 6, 10 and 14 weeks of age).…”

High residual prevalence of vaccine-serotypeStreptococcus pneumoniaecarriage after introduction of a pneumococcal conjugate vaccine in Malawi: a prospective serial cross-sectional study

“…The 18% residual aggregated VT carriage prevalence among PCV-vaccinated children was consistent with the 16.5% previously reported among PCV-vaccinated children 1-4 years old in northern Malawi, 3.5 years after PCV13 introduction. 11 Though these reported residual VT carriage prevalences were lower than that observed in northern Malawi before vaccine introduction (28%), 11 they did not reach the substantially lower levels rapidly achieved in high-income low-carriage prevalence settings (<5%) associated with control of carriage and transmission. [22][23][24] VT carriage dynamics did not conform to a simple exponential distribution, with slightly higher VT carriage prevalence among PCV-vaccinated children under 4 years of age than older vaccinated children.…”

“…7 Pneumococcal epidemiology in sub-Saharan Africa is characterised by high rates of carriage and transmission, differing markedly from high-income settings. 8,9 Carriage studies pre-dating PCV introduction in Kenya, 8 Mozambique, 10 Malawi, 11 The Gambia, 12 and South Africa 13 , for example, reported VT carriage prevalences ranging from 49.7% to 28.2% in under 5s, with colonisation occurring rapidly early in life. 14 Vaccine trials and post-routine-introduction studies in Africa have demonstrated substantial direct effects of PCV against IPD, pneumonia, and all-cause mortality among young children.…”