Table 3 Effectiveness of the mRNA-1273 vaccine against B.1.1.7 and B.1.351 infections and against severe, critical or fatal COVID-19 disease ≥14 days after the first dose and ≥14 days after the second dose

	≥14 Days after first dose and no second dose					≥14 Days after second dose
	Cases, n (PCR-positive)		Controls, n (PCR-negative)		Effectiveness, % (95% CI)^a	Cases, n (PCR-positive)		Controls, n (PCR-negative)		Effectiveness, % (95% CI)^a
	Vaccinated	Unvaccinated	Vaccinated	Unvaccinated		Vaccinated	Unvaccinated	Vaccinated	Unvaccinated
Effectiveness against infection
Any infection with the B.1.1.7 variant^b	44	23,860	365	23,539	88.1 (83.7–91.5)	0	21,305	47	21,258	100.0 (91.8–100.0)
Any infection with the B.1.351 variant^c	419	47,872	1,067	47,224	61.3 (56.5–65.5)	6	44,731	165	44,572	96.4 (91.9–98.7)
Effectiveness against disease
Any severe, critical or fatal disease with any SARS-CoV-2 infection^d	23	4,067	122	3,968	81.6 (71.0–88.8)	1	3,393	23	3,371	95.7 (73.4–99.9)

^aVaccine effectiveness was estimated using the test-negative, case-control study design^17,18.
^bAny B.1.1.7 PCR-confirmed infection. A B.1.1.7 infection is proxied as an S-gene target failure case using the TaqPath COVID-19 Combo Kit platform (Thermo Fisher Scientific¹⁹), applying the criterion of PCR cycle threshold value ≤30 for both the N and ORF1ab genes but a negative outcome for the S-gene^20,21,22. The median date of vaccination with first dose was 8 April for cases and 2 April for their matched controls.
^cAny B.1.351 PCR-confirmed infection. With essentially only B.1.351 and B.1.1.7 cases identified in the viral genome sequencing and the multiplex RT–qPCR variant screening between 8 March and 10 May 2021 (ref. ⁷), a B.1.351 infection is proxied as the complement of the B.1.1.7 criterion—that is, any infection with a Ct value ≤30 for the N, ORF1ab and S genes between the above dates. The median date of vaccination with first dose was 4 April for cases and 3 April for their matched controls.
^dAny PCR-confirmed infection that led to severe, critical or fatal COVID-19 disease. With the predominance of both B.1.1.7 and B.1.351 variants during the study period, this effectiveness is a combined measure against both of these variants. Severe disease, critical disease and COVID-19 death were defined based on the World Health Organization criteria for classification of SARS-CoV-2 infection severity²³ and COVID-19-related death²⁴.

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