Pneumococcal Acquisition among Infants Exposed to HIV in Rural Malawi

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 HIVstatus (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.

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

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

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

Full article at:   http://goo.gl/iStGNB

By:   Heinsbroek E, Tafatatha T, Chisambo C, Phiri A, Mwiba O, Ngwira B, Crampin AC, Read JM, French N.

Correspondence to Prof. Neil French, Department of Clinical Infection, Microbiology and Immunology, Institute of Infection and Global Health, University of Liverpool, Ronald Ross Building, 8 West Derby Street, Liverpool L69 7BE, United Kingdom (e-mail: ku.ca.looprevil@hcnerf).

Am J Epidemiol. 2016 Jan 1;183(1):70-8. doi: 10.1093/aje/kwv134. Epub 2015 Dec 1.

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Persisting High Prevalence of Pneumococcal Carriage among HIV-Infected Adults Receiving Antiretroviral Therapy in Malawi

HIV-infected adults have high rates of pneumococcal carriage and invasive disease. We investigated the effect of antiretroviral therapy (ART) on pneumococcal carriage in HIV-infected adults prior to infant pneumococcal conjugate vaccine (PCV) rollout.

We recruited HIV-infected adults newly attending a rural HIV clinic in northern Malawi between 2008 and 2010. Nasopharyngeal samples were taken at baseline and after 6, 12, 18 and 24 months. We compared pneumococcal carriage by ART status using generalized estimated equation models adjusted for CD4⁺ cell count, sex, seasonality, and other potential confounders.

In total, 336 individuals were included, of which 223 individuals started ART during follow-up. Individuals receiving ART had higher pneumococcal carriage than individuals not receiving ART (25.9 vs. 19.8%, P = 0.03) particularly for serotypes not included in PCV13 (16.1 vs. 9.6% P = 0.003). Following adjustment, increased carriage of non-PCV13 serotypes was still observed for individuals on ART, but results for all serotypes were nonsignificant.

Pneumococcal carriage in HIV-infected adults in Malawi remained high despite use of ART, consistent with failure of mucosal immune reconstitution in the upper respiratory tract. There was evidence of increased carriage of non-PCV13 serotypes. HIV-infected adults on ART could remain an important reservoir for pneumococcal diversity post infant pneumococcal vaccine introduction. Control of pneumococcal disease in African HIV remains a priority.

Below:  Pneumococcal colonization and median CD4+ cell count on baseline and by month since ART/month since baseline in patients receiving ART or not

Below:  Carriage of serotypes by ART status.

(a) Serotypes included in PCV13. (b) Serotypes not included in PCV13. ∗Factor typing not done, ∗∗Not able to establish factor typing. ART, antiretroviral therapy; PCV, pneumococcal conjugate vaccine.

Below: Seasonality of pneumococcal carriage.

(a) Crude carriage prevalence; (b) Fitted parametric spline from adjusted generalized estimated equations model. Grey area represents 95% confidence intervals. Black horizontal bars represent months in the rainy season (December–April).

Full article at: http://goo.gl/dOIO3d

By: Ellen Heinsbroek,a Terence Tafatatha,b Amos Phiri,b Bagrey Ngwira,b,c Amelia C. Crampin,b,d Jonathan M. Read,e andNeil Frencha

aDepartment of Clinical Infection, Microbiology, Institute of Infection and Global Health, University of Liverpool, UK

bKaronga Prevention Study, Chilumba

cThe Polytechnic, University of Malawi, Blantyre, Malawi

dDepartment of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London

eDepartment of Epidemiology and Population Health, Institute of Infection and Global Health, University of Liverpool, UK. 

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