Regular universal screening for SARS-CoV-2 infection may not allow reopening of society after controlling a pandemic wave
Abstract
Background
To limit societal and economic costs of lockdown measures, public health strategies are needed that control the spread of SARS-CoV-2 and simultaneously allow lifting of disruptive measures. Regular universal random screening of large proportions of the population regardless of symptoms has been proposed as a possible control strategy.
Methods
We developed a mathematical model that includes test sensitivity depending on infectiousness for PCR-based and antigen-based tests, and different levels of onward transmission for testing and non-testing parts of the population. Only testing individuals participate in high-risk transmission events, allowing more transmission in case of unnoticed infection. We calculated the required testing interval and coverage to bring the effective reproduction number due to universal random testing ( R rt ) below 1, for different scenarios of risk behavior of testing and non-testing individuals.
Findings
With R 0 = 2.5, lifting all control measures for tested subjects with negative test results would require 100% of the population being tested every three days with a rapid test method with similar sensitivity as PCR-based tests. With remaining measures in place reflecting R e = 1.3, 80% of the population would need to be tested once a week to bring R rt below 1. With lower proportions tested and with lower test sensitivity, testing frequency should increase further to bring R rt below 1. With similar R e values for tested and non-tested subjects, and with tested subjects not allowed to engage in higher risk events, at least 80% of the populations needs to test every five days to bring R rt below. The impact of the test-sensitivity on the reproduction number is far less than the frequency of testing.
Interpretation
Regular universal random screening followed by isolation of infectious individuals is not a viable strategy to reopen society after controlling a pandemic wave of SARS-CoV-2. More targeted screening approaches are needed to better use rapid testing such that it can effectively complement other control measures.
Funding
RECOVER (H2020-101003589) (MJMB), ZonMw project 10430022010001 (MK, HH), FCT project 131_596787873 (GR). ZonMw project 91216062 (MK)
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