%0 Journal Article %A Joshua G. Petrie %A Emily T. Martin %A Rachel Truscon %A Emileigh Johnson %A Caroline K. Cheng %A EJ McSpadden %A Ryan E. Malosh %A Adam S. Lauring %A Lois E. Lamerato %A Maryna C. Eichelberger %A Jill M. Ferdinands %A Arnold S. Monto %T Evaluation of correlates of protection against influenza A(H3N2) and A(H1N1)pdm09 infection: Applications to the hospitalized patient population %D 2018 %R 10.1101/416628 %J bioRxiv %P 416628 %X Background Influenza vaccines are important for prevention of influenza-associated hospitalization. Assessments of serologic correlates of protection can support interpretation of influenza vaccine effectiveness evaluations in hospitalized populations.Methods Serum specimens collected at admission from adults hospitalized for treatment of acute respiratory illnesses during two influenza seasons were tested in hemagglutination-inhibition (HAI) and neuraminidase-inhibition (NAI) assays. We evaluated the suitability of these specimens as proxies for pre-infection immune status, and measured associations between antibody titers and influenza vaccination and infectionResults Specimens were collected within 3 days of illness onset from 65% of participants; geometric mean titers (GMTs) did not vary by day of collection. In both seasons, vaccinated participants had higher HAI and NAI GMTs than unvaccinated participants. HAI titers against the 2014-2015 A(H3N2) vaccine strain did not correlate with protection from infection with antigenically-drifted A(H3N2) viruses that circulated that season. In contrast, higher HAI titers against the A(H1N1)pdm09 vaccine strain were associated with reduced odds of A(H1N1)pdm09 infection in 2015-2016.Conclusions Serum collected after hospital admission can be used to assess correlates of protection against influenza infection. Broader implementation of similar studies would provide an opportunity to understand the successes and shortcomings of current influenza vaccines.We thank Jin Gao and Laura Couzens for technical support and are indebted to St Jude Children’s Research Hospital for plasmids that were used to generate reassortant influenza viruses. %U https://www.biorxiv.org/content/biorxiv/early/2018/09/20/416628.full.pdf