Table 2.

Comparison of case investigation and contact tracing’s (CICT) impact during various periods in Vermont, by dominating variant transmission, 2020–2021.

Dominant strain	Original strain	Delta variant	Delta variant
Study period (Dates covered)	Period OS (Nov. 25, 2020–Jan. 19, 2021)	Period D1 (Aug. 01–Sept. 25, 2021)	Period D2 (Sept. 26–Nov. 20, 2021)
Estimated CICT impact
Cases averted	7810	1437	9970
Percentage reduction in COVID-19 cases*	55.4%	14.6%	40.4%

*The number of cases averted by CICT among every 100 cases not averted by vaccine or other nonpharmaceutical interventions (NPIs; such as facemask policies, large gathering restrictions, and school/business closures).