Over five seasons, we determined the proportion of outpatients with laboratory-confirmed, influenza-associated illness who were hospitalized within 30 days following the outpatient visit. Overall, 136 (1.7%) of 7813 influenza-positive patients were hospitalized a median of 4 days after an outpatient visit. Patients aged ≥ 65 years and those with high-risk conditions were at increased risk of hospitalization. After controlling for age and high-risk conditions, vaccination status and infecting influenza virus type were not associated with hospitalization risk among adults.
Appiah GD, Chung JR, Flannery B, Havers FP, Zimmerman RK, Nowalk MP, Monto AS, Martin ET, Gaglani M, Murthy K, Jackson LA, Jackson ML, McLean HQ, Belongia EA, Fry AM. (2019). Hospitalization following outpatient medical care for influenza: US influenza vaccine effectiveness network, 2011-12-2015-16. Influenza and other respiratory viruses, 13(2)