COVID-19 in Military Recruits

Military bases were sites of major outbreaks during the 1918–1919 influenza pandemic, and military recruits undergoing basic training suffered high rates of both group A streptococcal and meningococcal infections until effective control measures were developed between the 1950s and 1970s. Given this history, the U.S. Marine Corps instituted public health measures in the spring of 2020 to prevent SARS-CoV-2 infections among recruits undergoing basic training and now provide an initial report on the program.

The measures included a 2-week home quarantine prior to arrival at basic training, a second 2-week quarantine on base, polymerase chain reaction (PCR) testing immediately following the second quarantine, housing in double occupancy rooms, mask-wearing at all times except when eating or sleeping, social distancing, daily symptom and temperature monitoring, and restriction to the basic training base. Additionally, at the time of entry on the base, recruits were asked to consent to participating in a prospective trial with weekly SARS-CoV-2 PCR testing and immunoglobulin G antibody assessment.

Between May and July 2020, 1848 (58.8%) of 3143 eligible recruits participated in the trial, of whom 5.8% had baseline SARS-CoV-2 antibodies and 0.9% were PCR positive but asymptomatic. By day 14 of the on-base quarantine, 1.9% of previously negative participants were PCR positive, as were 1.7% of the nonparticipant recruits. Whole-genome sequencing identified six independent transmission clusters that occurred during the quarantine. Most recruits who tested positive were asymptomatic, and no infected individuals were identified by daily temperature and symptom screening.