Testing and Vaccination to Reduce the Impact of COVID-19 in Nursing Homes: An Agent-Based Approach

Gomez-Vazquez, J. P.; Garcia, y.; Schmidt, A. J.; Martinez-Lopez, B.; Nuno, M.

Background: Efforts to protect residents in nursing homes involve non-pharmaceutical interventions, testing, and vaccine. We sought to quantify the effect of testing and vaccine strategies on the attack rate, length of the epidemic, and hospitalization. Methods: We developed an agent-based model to simulate the dynamics of SARS-CoV-2 transmission in a nursing home with resident and staff agents. Interactions between 172 residents and 170 staff were assumed based on data from a nursing home in Los Angeles, CA. We simulated scenarios assuming different levels of non-pharmaceutical interventions, testing frequencies, and vaccine efficacy to block transmission. Results: Under the hypothetical scenario of widespread SARS-CoV-2 in the community, 3-day testing frequency minimized the attack rate and the time to eradicate an outbreak. Prioritization of vaccine among staff or staff and residents minimized the cumulative number of infections and hospitalization, particularly in the scenario of high probability of an introduction. Reducing the probability of a virus introduction reduced the demand on testing and vaccine to reduce infections and hospitalizations. Conclusions: Improving frequency of testing from 7-days to 3-days minimized the number of infections and hospitalizations, despite widespread community transmission. Vaccine prioritization of staff provides the best protection strategy, despite high risk of a virus introduction.