SARS-CoV-2 VACCINE EFFECTIVENESS IN A COHORT OF ACTIVE-DUTY US MILITARY PERSONNEL

ABSTRACT

Background: The US Defense Dept launched its COVID-19 vaccination program in Dec 20. The VIRAMP study was designed to address knowledge gaps in US military personnel including vaccine effectiveness against asymptomatic infection, viral carriage and transmission, and durability of protection. Method(s) Military members who had received >=1 dose of an FDA-authorized COVID-19 vaccine were enrolled at 3 sites in Texas May 21-Mar 22 and followed for up to 24 months after first dose. Study activities comprised of three in-person study visits and remote data collection weekly and monthly questionnaires, self-collection of blood (monthly) and saliva twice weekly (more frequently if symptomatic). Participants shipped self-collected specimens for Ab analyses and SARS-CoV-2 PCR and sequencing. We report an interim analysis on data collected through May 22. Result(s) Participants included 957 military members (60% male, 40% female), with 69% identifying as White, 15% Black/African American, 23% LatinX. Participants were Officers (38%) and Enlisted (62%);54% were healthcare workers. The majority (92.5%) received the Pfizer/BioNTech monovalent A/ Wuhan COVID-19 vaccine;30% of participants received one booster dose. One or more breakthrough infections (bti), defined as positive saliva SARS-CoV-2 PCR, were detected in 228 (24%) participants (36 Delta, 192 Omicron). No differences were detected in rates of symptomatic vs asymptomatic bti by variant or time since last vaccine. Mean age was greater for participants with bti vs those without (35.4 (+/- 7.7) years vs 32 (+/- 8.2) years;p< 0.0001), but no differences were noted by sex, race, or ethnicity. Symptomatic infections (defined as >=2 symptoms) were detected in 43% of participants, whereas 35% of bti were asymptomatic;there were no hospitalizations or deaths. A trend towards reduced duration of saliva positivity was noted in Omicron infections in the 4 months following booster dose compared to infections in the 4 months following primary series (5.3 days vs 12.4 days;p=0.0645). Conclusion(s) Approximately 1/4 of participants had bti in the first year, spanning the evolving epi and vaccination landscape of the pandemic, with about 1/3 demonstrating asymptomatic infection. A trend towards shorter duration of viral carriage following booster dose was noted in Omicron infections. The VIRAMP study demonstrated that prospective surveillance in a large, diverse cohort of US military members utilizing remote specimen and questionnaire collection is operationally feasible.