Vaccine effectiveness against influenza-associated hospitalization among children aged < 13 years using a hospital-based surveillance system in Minnesota, 2013 – 2016. (4th October 2017)

• Record Type: Journal Article
• Authors: Fowlkes, Ashley; Friedlander, Hannah; Steffens, Andrea; Como-Sabetti, Kathryn; Boxrud, Dave; Bistodeau, Sarah; Strain, Anna; Ferdinands, Jill M; Chaves, Sandra S; Reed, Carrie; Lynfield, Ruth
• Is Part Of: Open forum infectious diseases. Volume 4(2017)Supplement 1
• Page Start: S60
• Page End: S60
• Publication Date: 2017-10-04
• Subjects: Communicable diseases -- Periodicals; Medical microbiology -- Periodicals; Infection -- Periodicals; 616.9
• DOI: 10.1093/ofid/ofx162.142
• Languages: English
• ISSNs: 2328-8957

Abstract

Abstract: Background: Due to marked variability in circulating influenza viruses each year, annual evaluation of the vaccine&#39;s effectiveness against severe outcomes is essential. We used the Minnesota Department of Health&#39;s (MDH) Severe Acute Respiratory Illness (SARI) surveillance to evaluate vaccine effectiveness (VE) against influenza-associated hospitalization over three influenza seasons. Methods: Residual respiratory specimens from patients admitted with SARI were sent to the MDH laboratory for influenza RT-PCR testing. Medical records were reviewed to collect patient data. Vaccination history was verified using the state immunization registry. We included patients aged ≥6 months to &lt; 13 years, after which immunization reporting is not required, hospitalized from the earliest influenza detection after July through April each year. We defined vaccinated patients as those ≥1 dose of influenza vaccine in the current season. Children aged &lt; 9 years with no history of vaccination were considered vaccinated if 2 were doses given a month apart. Partially vaccinated children were excluded. We estimated VE as 1 minus the adjusted odds ratio (x100%) of influenza vaccination among influenza cases vs. negative controls, controlling for age, race, days from onset to admission, comorbidities, and admission month. Results: Among 2198 SARI patients, 763 (35%) were vaccinated for influenza, 180 (8.2%) were partially vaccinated, and 1255 (57%) were unvaccinated. Influenza was detected among 202 (9.2%) children, and significantly more frequently among children aged ≥5 years (17%) compared with younger children (7.4%). The adjusted VE in 2013–14 was 68% (95% Confidence Interval: 34, 85), but was non-significant during the 2014–15 and 2015–16 seasons (Figure). Estimates of VE by influenza A subtypes varied substantially by year; VE against influenza B viruses was significant, but could not be stratified by year. VE was impacted when live attenuated influenza vaccine recipients were excluded. Conclusion: We report moderately high influenza VE in 2013–14 and a point estimate higher than other published estimates from outpatient data in 2014–15. These results, underscore the importance of influenza vaccination to prevent severe outcomes such as hospitalization. Disclosures: All authors: No reported disclosures.