Influenza vaccination in HIV-infected individuals: systematic review and assessment of quality of evidence related to vaccine efficacy, effectiveness and safety

Background: Influenza infection in HIV-infected individuals is associated with increased severity of illness. We performed a systematic review of the available evidence on efficacy, effectiveness and safety of seasonal influenza vaccination in HIV-infected individuals.

Design: Systematic review, meta-analysis and assessment of evidence quality.

Methods: Using a previous systematic review as starting point, we searched MEDLINE, EMBASE and Cochrane data base for studies on efficacy, effectiveness or safety of trivalent inactivated influenza vaccines (TIV) in HIV-infected individuals. Evidence quality was assessed for each outcome using the GRADE methodology.

Results: Three randomized-controlled trials and three cohort studies were identified, including a total of 1562 HIV-infected individuals. In adults, TIV prevented laboratory-confirmed influenza with a pooled efficacy of 85% (95% CI, 22-97%) (evidence quality: moderate), but no significant effects on other clinical outcomes were observed (evidence quality: moderate to low). One cohort study showed an effectiveness of 71% (95% CI, 44-85%) for prevention of laboratory-confirmed influenza, whereas no effect on influenza-like illness was found. However, risk of bias was high in all observational studies. In children aged 6-59 months, efficacy of TIV in preventing laboratory-confirmed influenza was 11% (95% CI, -30 to 54%) (evidence quality: moderate). Regarding other endpoints, no statistically significant effects were reported (evidence quality: moderate to low). No severe adverse events following influenza vaccination were observed in these studies.

Conclusion: This systematic review indicates that TIV is effective in preventing influenza infection in HIV-infected adults but not in young children. For both age-groups, only limited evidence exists for other outcomes, indicating a need for further studies.