Daily Rapid Antigen Exit Testing to Tailor University COVID-19 Isolation Policy

Abstract

We evaluated daily rapid antigen test (RAT) data from 323 COVID-19-positive university students in Connecticut, USA, during an Omicron-dominant period. Day 5 positivity was 47% for twice-weekly screeners and 26%-28% for less-frequent screeners, approximately halving each subsequent day. Testing negative >10 days before diagnosis (event time ratio (ETR) 0.85 [95% CI 0.75-0.96]) and prior infection >90 days (ETR 0.50 [95% CI 0.33-0.76]) were significantly associated with shorter RAT positivity duration. Symptoms before or at diagnosis (ETR 1.13 [95% CI 1.02-1.25]) and receipt of 3 vaccine doses (ETR 1.20 [95% CI 1.04-1.39]) were significantly associated with prolonged positivity. Exit RATs enabled 53%-74% of students to leave isolation early when they began isolation at the time of the first positive test, but 15%-22% remained positive beyond the recommended isolation period. Factors associated with RAT positivity duration should be further explored to determine relationships with infection duration.

Keywords: COVID-19; SARS-CoV-2; United States; coronavirus disease; direct-to-consumer screening and testing; epidemiology; patient isolation; respiratory infections; severe acute respiratory syndrome coronavirus 2; student health services; viruses; zoonoses.

Figure

Rapid antigen testing results by isolation day and positivity duration by days since the last negative test category in study of students isolated for positive SARS-CoV-2 results. Left axis shows percent still positive of the original study population; right axis shows the number tested positive on each isolation day. A) Last negative test ≤4 days earlier (N = 177). B) Last negative test 5–9 days earlier (N = 47). C) Last negative test ≥10 days before the earliest test (inconclusive or positive) (N = 91). One person was removed due to missing last negative test data, and 10 persons were removed due to testing inconclusive initially but counted the first positive test as day 0.