Impact of HIV on the burden and severity of influenza illness in Malawian adults: a prospective cohort and parallel case-control study

Abstract

Background

The impact of HIV infection on influenza incidence and severity in adults in sub-Saharan Africa is unclear. Seasonal influenza vaccination is recommended for HIV-infected persons in developed settings, but is rarely implemented in Africa.

Methods

We conducted a prospective cohort study to compare the incidence of laboratory-confirmed influenza illness between HIV-infected and HIV-uninfected adults in Blantyre, Malawi. In a parallel case-control study, we explored risk factors for severe influenza presentation of severe (hospitalized lower respiratory tract infection (LRTI)), and mild influenza (influenza-like illness (ILI)).

Results

The cohort study enrolled 608 adults (360 (59%) HIV-infected). Between April 2013 and March 2015, 24/229 (10.5%) ILI episodes in HIV-infected and 5/119 (4.2%) in HIV-uninfected adults were influenza PCR positive (incidence rates 46.0 vs. 14.5 per 1000 person years, incidence rate ratio 2.75; 95% confidence interval [CI] 1.02-7.44; p=0.03, adjusted for age, gender, household crowding and food security). In the case control study, influenza was identified in 56/518 (10.8%) patients with hospitalized LRTI, and 88/642 (13.7%) with ILI. HIV prevalence among influenza-positive cases and controls were 69.6% and 29.6% respectively. HIV was a significant risk factor for severe influenza (odds ratio 4.98, 95%CI 2.09-11.88, p<0.001; population attributable fraction 57%, adjusted for season, sanitation facility and food security).

Conclusions

HIV is an important risk factor for influenza-associated ILI and severe presentation in this high HIV prevalence African setting. Targeted influenza vaccination of HIV-infected African adults should be re-evaluated and the optimal mechanism for vaccine introduction in overstretched health systems needs to be determined.