Assessment of an Enhanced COVID-19 Case and Contact Management Protocol in Controlling a Sars-Cov-2 Alpha (B.1.1.7) Variant Outbreak on a Construction Site

BACKGROUND: To control the spread of SARS-CoV-2 variants of concern (VOCs), Kingston, Frontenac, and Lennox & Addington (KFL&A) Public Health implemented a more stringent COVID-19 case and contact management (CCM) protocol than what was used across Ontario at the time. Researchers describe epidemiological data and public health measures employed during one of the largest COVID-19 outbreaks in the KFL&A region at the time, caused by the SARS-CoV-2 Alpha (B.1.1.7) VOC, to assess this enhanced protocol.

METHODS: Researchers obtained line lists of workers associated with the construction site outbreak, and subsequent cases and contacts from case investigators. Case testing, mutation status, and whole genome sequencing were conducted by Public Health Ontario Laboratories.

RESULTS: From 409 high-risk contacts of the outbreak, 109 (27%) developed COVID-19. Three generations of spread were associated with the outbreak, affecting seven public health regions across three provinces. Using an enhanced approach to the CCM, KFL&A Public Health caught 15 cases that could have been missed by standard provincial protocols.

CONCLUSIONS: Rapid initial spread within the construction site produced a relatively high attack rate among workers (26%) and their immediate contacts (34%). KFL&A Public Health’s implementation of stringent CCM protocols and fast testing turn-around time effectively curbed the spread of the disease in subsequent generations – illustrated by the large reduction in attack rate (34%–14%) and cases (50–10) between the second and third generations. Lessons learned from this analysis may inform guidance on the CCM for future SARS-CoV-2 VOCs as well as other highly transmissible communicable diseases.