Pneumococcal Acquisition Among Infants Exposed to HIV in Rural Malawi: A Longitudinal Household Study

Abstract

The prevalence of Streptococcus pneumoniae (pneumococcus) carriage is higher in adults who are infected with human immunodeficiency virus (HIV) than in adults who are not. We hypothesized that infants exposed to HIV become carriers of nasopharyngeal pneumococcus earlier and more frequently than infants who are not exposed to HIV. We compared infant pneumococcal acquisition by maternal HIV status and household exposure in Karonga District, Malawi, in 2009-2011, before the introduction of pneumococcal conjugate vaccine. Nasopharyngeal swabs were collected every 4-6 weeks in the first year of life from infants with known HIV-exposure status, their mothers, and other household members. We studied infant pneumococcal acquisition by maternal HIV status, serotype-specific household exposure, and other risk factors, including seasonality. We recruited 54 infants who were exposed to HIV and 131 infants who were not. There was no significant difference in pneumococcal acquisition by maternal HIV status (adjusted rate ratio (aRR) = 1.00, 95% confidence interval (CI): 0.87, 1.15). Carriage by the mother was associated with greater acquisition of the same serotype (aRR = 3.09, 95% CI: 1.47, 6.50), but the adjusted population attributable fraction was negligible (1.9%, 95% CI: 0.0, 4.3). Serotype-specific exposure to children under 5 years of age was associated with higher acquisition (aRR = 4.30, 95% CI: 2.80, 6.60; adjusted population attributable fraction = 8.8%, 95% CI: 4.0, 13.4). We found no evidence to suggest that maternal HIV infection would affect the impact of pneumococcal vaccination on colonization in this population.

Keywords: Africa; HIV; Streptococcus pneumoniae; carriage; cohort studies; infant; transmission.

Figure 1.

Prevalence of pneumococcal carriage by age of the index infant (weeks), Karonga District, Malawi, 2009–2011. Bars, 95% confidence intervals.

Figure 2.

Kaplan-Meier plot for time to first acquisition of pneumococcal carriage in infants by human immunodeficiency virus (HIV) exposure status, Karonga District, Malawi, 2009–2011.

Figure 3.

Kaplan-Meier plot for time to first acquisition of pneumococcal carriage in infants by the presence or absence of other children less than 5 years of age in the household, Karonga District, Malawi, 2009–2011.

Figure 4.

Fitted parametric seasonal trend in the incidence of pneumococcal carriage among infants in Karonga District, Malawi, 2009–2011. Gray areas, 95% confidence intervals.

Figure 5.

Nonparametric spline fitted to the secular trend in pneumococcal carriage incidence in infants, Karonga District, Malawi, 2009–2011. Gray areas, 95% confidence intervals.