Mathematical Modeling to Inform Vaccination Strategies and Testing Approaches for Coronavirus Disease 2019 (COVID-19) in Nursing Homes

• Published in: Clinical infectious diseases Vol. 74; no. 4; pp. 597 - 603
• Main Authors: Kahn, Rebecca, Holmdahl, Inga, Reddy, Sujan, Jernigan, John, Mina, Michael J, Slayton, Rachel B
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 01.03.2022
• Subjects: COVID-19 - prevention & control; Humans; Major and Commentaries; Nursing Homes; SARS-CoV-2; Skilled Nursing Facilities; United States; Vaccination; United States; COVID-19; vaccine efficacy; nursing homes
• ISSN: 1058-4838; 1537-6591; 1537-6591
• DOI: 10.1093/cid/ciab517

Abstract Background Nursing home residents and staff were included in the first phase of coronavirus disease 2019 vaccination in the United States. Because the primary trial endpoint was vaccine efficacy (VE) against symptomatic disease, there are limited data on the extent to which vaccines protect against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the ability to infect others (infectiousness). Assumptions about VE against infection and infectiousness have implications for changes to infection prevention guidance for vaccinated populations, including testing strategies. Methods We use a stochastic agent-based Susceptible-Exposed-Infectious (Asymptomatic/Symptomatic)-Recovered model of a nursing home to simulate SARS-CoV-2 transmission. We model 3 scenarios, varying VE against infection, infectiousness, and symptoms, to understand the expected impact of vaccination in nursing homes, increasing staff vaccination coverage, and different screening testing strategies under each scenario. Results Increasing vaccination coverage in staff decreases total symptomatic cases in the nursing home (among staff and residents combined) in each VE scenario. In scenarios with 50% and 90% VE against infection and infectiousness, increasing staff coverage reduces symptomatic cases among residents. If vaccination only protects against symptoms, and asymptomatic cases remain infectious, increased staff coverage increases symptomatic cases among residents. However, this is outweighed by the reduction in symptomatic cases among staff. Higher frequency testing—more than once weekly—is needed to reduce total symptomatic cases if the vaccine has lower efficacy against infection and infectiousness, or only protects against symptoms. Conclusions Encouraging staff vaccination is not only important for protecting staff, but might also reduce symptomatic cases in residents if a vaccine confers at least some protection against infection or infectiousness. The extent of efficacy of severe acute respiratory syndrome coronavirus 2 vaccines against infection, infectiousness, or disease affects strategies for vaccination and testing in nursing homes. If vaccines confer some protection against infection or infectiousness, encouraging vaccination in staff may reduce symptomatic cases in residents.