The vaccination threshold for SARS-CoV-2 depends on the indoor setting and room ventilation

A Mikszewski; L Stabile; G Buonanno; L Morawska

doi:10.1186/s12879-021-06884-0

The vaccination threshold for SARS-CoV-2 depends on the indoor setting and room ventilation

BMC Infect Dis. 2021 Nov 26;21(1):1193. doi: 10.1186/s12879-021-06884-0.

Authors

A Mikszewski^{1

2}, L Stabile³, G Buonanno^{1

3}, L Morawska^{4

5}

Affiliations

¹ International Laboratory for Air Quality and Health, Queensland University of Technology, 2 George Street, Brisbane, QLD, 4001, Australia.
² CIUS Building Performance Lab, The City University of New York, New York, NY, 10001, USA.
³ Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy.
⁴ International Laboratory for Air Quality and Health, Queensland University of Technology, 2 George Street, Brisbane, QLD, 4001, Australia. l.morawska@qut.edu.au.
⁵ Global Centre for Clean Air Research (GCARE), Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH, UK. l.morawska@qut.edu.au.

Abstract

Background: Effective vaccines are now available for SARS-CoV-2 in the 2nd year of the COVID-19 pandemic, but there remains significant uncertainty surrounding the necessary vaccination rate to safely lift occupancy controls in public buildings and return to pre-pandemic norms. The aim of this paper is to estimate setting-specific vaccination thresholds for SARS-CoV-2 to prevent sustained community transmission using classical principles of airborne contagion modeling. We calculated the airborne infection risk in three settings, a classroom, prison cell block, and restaurant, at typical ventilation rates, and then the expected number of infections resulting from this risk at varying percentages of occupant immunity.

Results: We estimate the setting-specific immunity threshold for control of wild-type SARS-CoV-2 to range from a low of 40% for a mechanically ventilation classroom to a high of 85% for a naturally ventilated restaurant.

Conclusions: If vaccination rates are limited to a theoretical minimum of approximately two-thirds of the population, enhanced ventilation above minimum standards for acceptable air quality is needed to reduce the frequency and severity of SARS-CoV-2 superspreading events in high-risk indoor environments.

Keywords: Airborne transmission; SARS-CoV-2; Vaccination; Ventilation.

MeSH terms

Air Pollution, Indoor*
COVID-19*
Humans
Pandemics
SARS-CoV-2
Vaccination
Ventilation