Table 2. Attack rates in Vaxzevria-vaccinated and -unvaccinated residents and staff during a COVID-19 outbreak caused by the SARS-CoV-2 Delta variant in a care home, London, England, April 2021 (n = 36).

Cases	Attack rates				Reduction ratec
	Vaccinateda		Unvaccinatedb
	n/N	%	n/N	%
Staff	5/14	35.7	2/5	40	10.7
Residents	13/16	81.3	1/1	100	18.7

COVID-19: coronavirus disease; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.

^a Only those who have received 1 dose or < 14 days after dose 2 of Vaxzevria (ChAdOx1-S; AstraZeneca, Cambridge, United Kingdom) vaccine.

^b Excludes non-cases who had antibodies from previous SARS-CoV-2 infection based on serology.

^c Reduction rate = (AR unvaccinated - AR vaccinated)/AR unvaccinated x 100 where AR is attack rate.

Residents who did not consent to PCR testing were excluded.