Estimating the contribution of HIV-infected adults to household pneumococcal transmission in South Africa, 2016–2018: A hidden Markov modelling study
Date
2021-12-23
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Abstract
Human immunodeficiency virus (HIV) infected adults are at a higher risk of pneumococcal
colonisation and disease, even while receiving antiretroviral therapy (ART). To help evaluate potential indirect effects of vaccination of HIV-infected adults, we assessed whether
HIV-infected adults disproportionately contribute to household transmission of pneumococci. We constructed a hidden Markov model to capture the dynamics of pneumococcal
carriage acquisition and clearance observed during a longitudinal household-based nasopharyngeal swabbing study, while accounting for sample misclassifications. Households
were followed-up twice weekly for approximately 10 months each year during a three-year
study period for nasopharyngeal carriage detection via real-time PCR. We estimated the
effect of participant’s age, HIV status, presence of a HIV-infected adult within the household
and other covariates on pneumococcal acquisition and clearance probabilities. Of 1,684
individuals enrolled, 279 (16.6%) were younger children (<5 years-old) of whom 4 (1.5%)
were HIV-infected and 726 (43.1%) were adults (�18 years-old) of whom 214 (30.4%) were
HIV-infected, most (173, 81.2%) with high CD4+ count. The observed range of pneumococcal carriage prevalence across visits was substantially higher in younger children (56.9–
80.5%) than older children (5–17 years-old) (31.7–50.0%) or adults (11.5–23.5%). We estimate that 14.4% (95% Confidence Interval [CI]: 13.7–15.0) of pneumococcal-negative swabs were false negatives. Daily carriage acquisition probabilities among HIV-uninfected
younger children were similar in households with and without HIV-infected adults (hazard
ratio: 0.95, 95%CI: 0.91–1.01). Longer average carriage duration (11.4 days, 95%CI: 10.2–
12.8 vs 6.0 days, 95%CI: 5.6–6.3) and higher median carriage density (622 genome equivalents per millilitre, 95%CI: 507–714 vs 389, 95%CI: 311.1–435.5) were estimated in HIVinfected vs HIV-uninfected adults. The use of ART and antibiotics substantially reduced carriage duration in all age groups, and acquisition rates increased with household size.
Although South African HIV-infected adults on ART have longer carriage duration and density than their HIV-uninfected counterparts, they show similar patterns of pneumococcal
acquisition and onward transmission.