Risk factors for pneumococcal carriage in adults living with HIV on antiretroviral therapy in the infant pneumococcal vaccine era in Malawi.

Adults living with HIV (ALWHIV) on antiretroviral therapy (ART) are at high risk of pneumococcal carriage and disease. To help evaluate carriage risk in African ALWHIV at least 4-years after infant pneumococcal conjugate vaccination introduction in 2011, we assessed association between pneumococcal carriage and potential risk factors. Nasopharyngeal swabs were collected from adults aged 18-40 years attending an ART clinic during rolling, cross-sectional surveys in Blantyre, Malawi between 2015-2019. We fitted generalised additive models to estimate the risk of sex, social economic status (SES), living with a child <5y, and ART duration on carriage. Of 2,067 adults, median age was 33y (range 28-37), 1,427 (69.0%) were females, 1,087 (61.4%) were in low-middle socio-economic-status (SES), 910 (44.0%) were living with a child <5y, and median ART duration was 3.0 years (range 0.004-17). We estimated 38.2% and 60.6% reductions in overall and vaccine-serotype carriage prevalence. Overall carriage was associated with low SES, living with a child <5y and shorter duration on ART. By contrast, vaccine-type carriage was associated with living without a child <5y and male sex. Despite temporal reductions in overall and vaccine-serotype carriage, there is evidence of incomplete vaccine-serotype indirect protection. A targeted-vaccination campaign should be considered for ALWHIV, along with other public health measures to further reduce vaccine-serotype carriage and therefore disease.