RESUMO
BACKGROUND: Following COVID-19 exposure, the CDC recommends a 10-14 day quarantine for asymptomatic individuals and more recently a 7 day quarantine with a negative PCR test. We performed a university-based prospective student cohort study to determine if early PCR negativity predicts day 14 negativity. METHODS: We enrolled 101 asymptomatic, quarantining, students, performed nasopharyngeal swabs for viral testing on days 3 or 4, 5, 7, 10 and 14 and determined the proportion of concordant negative results for each day versus day 14 with a two-sided 95% exact binomial confidence interval. RESULTS: Overall, 14 of 90 (16%, 95% CI: 9% - 25%) tested positive while in quarantine, with 7 initial positive tests on day 3 or 4, 5 on day 5, 2 on day 7, and none on day 10 or 14. Rates of concordant negative test results are: day 5 vs. day 14 = 45/50 (90%, 95% CI: 78% - 97%); day 7 vs. day 14 = 47/52 (90%, 95% CI: 79% - 97%); day 10 vs. day 14 = 48/53 (91%, 95% CI:79% - 97%), with no evidence of different negative rates between earlier days and day 14 by McNemar's test, p > 0.05. CONCLUSIONS: The 16% positive rate supports the ongoing need to quarantine close contacts of COVID-19 cases, but this prospective study provides the first direct evidence that exposed asymptomatic students ages 18-44 years in a university setting are at low risk if released from quarantine at 7 days if they test negative PCR test prior to release.
