Influenza vaccine effectiveness among patients with high-risk medical conditions in the United States, 2012–2016

• DOI: 10.1016/j.vaccine.2018.10.093
• Publication Date: 2018-11-09T01:41:30Z
• Authors: Mei Shang; Jessie R. Chung; Michael L. Jackson; Lisa A. Jackson; Arnold S. Monto; Emily T. Martin; Edward A. Belongia; Huong Q. McLean; Manjusha Gaglani; Kempapura Murthy; Richard K. Zimmerman; Mary Patricia Nowalk; Alicia M. Fry; Brendan Flannery
• Keywords: Adult; Male; Adolescent; Influenza A Virus, H3N2 Subtype; Infant; Middle Aged; Medical Records; United States; 3. Good health; Influenza B virus; 03 medical and health sciences; Influenza A Virus, H1N1 Subtype; 0302 clinical medicine; Influenza Vaccines; Risk Factors; Case-Control Studies; Child, Preschool; Population Surveillance; Influenza, Human; Humans; Female; Child; Aged

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.Data from the U.S. Influenza Vaccine Effectiveness Network from 2012 to 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.Overall, 9643 (38%) of 25,369 patients enrolled during four influenza seasons had high-risk conditions; 2213 (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.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.