Did people’s behavior after receiving negative COVID-19 tests contribute to the spread?

Robertson, Leon S

BACKGROUND: Testing on demand for coronavirus disease (COVID-19) is hypothesized to increase spread of the virus as some persons who test negative falsely assume that they can engage in activities that increase spread. METHODS: Daily new COVID-19 hospitalization counts through 2020 from 25 countries that reported testing and hospitalizations were studied by regression of logarithms of new hospitalizations 14 days out against log(new hospitalizations on a given day), log(negative tests), log(positivity rate) and days since the first hospitalizations were reported. The regression coefficients were examined separately for periods in countries that were following three different testing policies. RESULTS: Corrected for the other factors, negative test numbers when tested on demand and tested if symptomatic only are associated with an increase in hospitalizations 14 days after the tests. When only the symptomatic and more vulnerable are tested, negative tests are associated with fewer hospitalizations 2 weeks out. CONCLUSIONS: A policy of testing only vulnerable populations, whether symptomatic or not, appears to avoid spreading the virus as a result of testing policy. False confidence of reduced risk among those who test negative may have contributed to the spread in countries that allowed testing on demand or testing only those who claimed to have symptoms.