2751. Pragmatic Assessment of Influenza Vaccine Effectiveness in the DoD (PAIVED): Methods

BACKGROUND: Most influenza vaccines come from inactivated virus grown in egg culture, and studies suggest that egg-adapted virus may have decreased immunogenicity in humans for certain influenza A strains. Cell culture-based and recombinant vaccines may be more immunogenic, but comparative studies are lacking. We are conducting a randomized, controlled trial of 3 FDA-licensed influenza vaccines (cell culture, recombinant, and egg culture) to assess differences in immunogenicity and effectiveness in adults. METHODS: A total of 10,650 eligible adults will be individually randomized 1:1:1 (cell culture, recombinant, or egg-based vaccine) over 2 influenza seasons (2018–2019 and 2019–2020) at military facilities in geographically diverse locations in the US Participants who are not military recruits will report the presence or absence of ILI symptoms on a weekly basis through an automated electronic (text message or email) survey; those who experience ILI symptoms will be scheduled for two in-person visits. Military recruits who experience an ILI report will report directly to clinic and will not receive weekly surveillance reminders (Figure 1). RESULTS: Enrollment for year 1 of PAIVED occurred November 7 to December 31, 2018 at 5 military bases. During this season, 1,623 participants were enrolled, among whom 34% were randomized to receive cell culture vaccine, 33% to recombinant vaccine, and 33% to egg-based vaccine. The participants were 61% active military, 19% retired military, and 20% military dependents. One quarter of the participants were women, and the participants were 18–88 years old, median 26 years of age. Among the 1,559 participants with complete data, 324 (21%) experienced ILI at least once. Blood and swab samples were successfully collected at visit 1 from 93% of the participants with case-defined ILIs. CONCLUSION: The initial phase of PAIVED successfully enrolled and randomized 1,623 participants during the 2018/2019 influenza season. Follow-up of this season’s participants is on-going. PAIVED will apply lessons learned during the 2018/2019 influenza season to the next season’s study implementation, with the goal of enrolling more than 9,000 additional participants through increasing the number of individuals enrolled at some sites and adding new sites to the trial. [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.