Factors associated with hospitalization for seasonal influenza in Morocco.

Background: Morocco is actively working towards expanding its influenza vaccine policy to cover high-risk groups, as recommended by the World Health Organization (WHO). Aims: We assessed the risk factors for influenza-associated hospitalization for severe acute respiratory infections (SARI) that occurred during the last 5 seasons. Methods: We conducted a retrospective, analytical study among patients recruited in the ambulatory and hospital sites of the influenza sentinel surveillance system in Morocco between 2014 and 2019. Using multiple logistic regression, we compared the characteristics of influenza-positive patients with SARI to those with influenza-like illness (ILI) to identify factors associated with severe disease. Results: We included 1323 positive influenza patients with either SARI (41.7%) or ILI diagnosis (58.3%). A(H1N1)pdm09, A(H3N2) and influenza B, respectively, contributed 49.2%, 29.5% and 20.6% of the cases. The main risk factors considered in the bivariate analysis were found in the multivariate analysis to be significantly associated with influenza-related hospitalization (SARI): age < 2 years (aOR = 7.08, P < 0.001); age ≥ 65 years (aOR = 3.59, P < 0.001); diabetes (aOR = 1.98, P = 0.017); obesity (aOR = 2.94, P = 0.034); asthma or chronic respiratory disease (aOR = 4.99, P < 0.001); chronic renal failure (aOR = 4.74, P = 0.005); pregnancy (aOR = 7.49, P < 0.001); and the A(H1N1)pdm09 subtype (aOR = 1.82, P < 0.001). Conclusion: This study provides epidemiological evidence for the expected benefit of an influenza vaccination strategy for high-risk groups as recommended by the WHO.