ABSTRACT
Background: Residents of care facilities for the elderly have accounted for a large proportion of all deaths due to COVID-19 globally. In Hong Kong, care home staff are required to undergo testing for SARS-CoV-2 every two weeks, regardless of symptoms. We aimed to optimize testing strategies in order to improve on existing screening programs.Methods: We estimated the reduced sensitivity of pooled PCR testing and used a decision analysis to determine the expected number of tests required. We assumed transmission occurred according to a time-varying Poisson process and that the time from infection to isolation followed a time-varying geometric distribution. We estimated the cumulative number of cases expected under syndromic surveillance, testing without pooling and pooled testing with pool sizes 2, 5 and 10 using an age of infection model.Findings: Assuming a prevalence of 0.02%, pooling 10 samples and conducting testing every two days instead of testing without pooling every 14 days could reduce the average size of an outbreak from between 2 and 14 cases (median 7 cases) to between 1 and 6 cases (median 2 cases). Pooling to allow for daily testing further reduced the average size of an outbreak from 4 cases to 1 case compared to weekly testing.Interpretation: Health authorities can improve on existing screening programs by employing pooled testing procedures and testing individuals more frequently to make the most use of available testing resources.Funding Information: This project was supported by a commissioned grant from the Health and Medical Research Fund, Food and Health Bureau, Government of the Hong Kong Special Administrative Region, and the Theme-based Research Scheme (Project No. T11-712/19-N) of the Research Grants Council of the Hong Kong SAR Government.Declaration of Interests: BJC consults for Roche, GSK, Moderna, AstraZeneca and Sanofi Pasteur and is supported by the AIR@innoHK program of the Innovation and Technology Commission of the Hong Kong SAR Government. The authors report no other potential conflicts of interest.Ethics Approval Statement: The study was approved by the Institutional Review Board of the University of Hong Kong.