Background: Annual influenza vaccination has been recommended for persons with high-risk conditions since the 1960s. However, few estimates of influenza vaccine effectiveness (VE) for persons with high-risk conditions are available. Methods: Data from the U.S. Influenza Vaccine Effectiveness Network from 2012‒2016 were analyzed to compare VE of standard-dose inactivated vaccines against medically-attended influenza among patients aged ≥6 months with and without high-risk medical conditions. Patients with acute respiratory illness were tested for influenza by RT-PCR. Presence of high-risk conditions and vaccination status were obtained from medical records. VE by influenza virus type/subtype and age group was calculated for patients with and without high-risk conditions using the test-negative design. Interaction terms were used to test for differences in VE by high-risk conditions. Results: Overall, 9,643 (38%) of 25,369 patients enrolled during four influenza seasons had high-risk conditions; 2,213 (23%) tested positive for influenza infection. For all ages, VE against any influenza was lower among patients with high-risk conditions (41%, 95% CI: 35%‒47%) than those without (48%, 95% CI: 43%‒52%; P-for-interaction = 0.02). For children aged <18 years, VE against any influenza was 51% (95% CI: 39%‒61%) and 52% (95% CI: 39%‒61%) among those with and without high-risk conditions, respectively ( P-for-interaction = 0.54). For adults aged ≥18 years, VE against any influenza was 38% (95% CI: 30%‒45%) and 44% (95% CI: 38%‒50%) among those with and without high-risk conditions, respectively ( P-for-interaction = 0.21). For both children aged <18 and adults aged ≥18 years, VEs against illness related to influenza A(H3N2), A(H1N1)pdm09, and influenza B virus infection were similar among those with and without high-risk conditions. Conclusions: Influenza vaccination provided protection against medically-attended influenza among patients with high-risk conditions, at levels approaching those observed among patients without high-risk conditions. Results from our analysis support recommendations of annual vaccination for patients with high-risk conditions.
【저자키워드】 Vaccine, Influenza, vaccine effectiveness, acute respiratory illness, high-risk medical conditions,