Effectiveness of BNT162b2 and mRNA-1273 COVID-19 vaccines against symptomatic SARS-CoV-2 infection and severe COVID-19 outcomes in Ontario, Canada: a test-negative design study

Abstract

Objectives: To estimate the effectiveness of one and two doses of mRNA COVID-19 vaccines against symptomatic infection and severe outcomes. Design: Using a test-negative design study and linked laboratory, vaccination, and health administrative databases, we estimated adjusted vaccine effectiveness (aVE) against symptomatic infection and severe outcomes (hospitalization or death) using multivariable logistic regression. Setting: Ontario, Canada between 14 December 2020 and 19 April 2021. Participants: Community-dwelling adults aged ≥16 years who were tested for SARS-CoV-2 and had COVID-19 symptoms. Interventions: Pfizer-BioNTech's BNT162b2 or Moderna's mRNA-1273 vaccine. Main outcome measures: Laboratory-confirmed SARS-CoV-2 identified by RT-PCR; hospitalization or death associated with SARS-CoV-2 infection. Results: Among 324,033 symptomatic individuals, 53,270 (16.4%) were positive for SARS-CoV-2 and 21,272 (6.6%) received 1 or more vaccine dose. Among test-positive cases, 2,479 (4.7%) had a severe outcome. aVE against symptomatic infection 14 days or more after receiving only 1 dose was 60% (95%CI, 57 to 64%), increasing from 48% (95%CI, 41 to 54%) at 14-20 days after the first dose to 71% (95%CI, 63 to 78%) at 35-41 days. aVE 7 days or more after receiving 2 doses was 91% (95%CI, 89 to 93%). Against severe outcomes, aVE 14 days or more after receiving 1 dose was 70% (95%CI, 60 to 77%), increasing from 62% (95%CI, 44 to 75%) at 14-20 days to 91% (95%CI, 73 to 97%) at 35 days or more, whereas aVE 7 days or more after receiving 2 doses was 98% (95%CI, 88 to 100%). For adults aged 70 years and older, aVE estimates were lower after receiving 1 dose, but were comparable to younger adults after 28 days. After 2 doses, we observed high aVE against E484K-positive variants. Conclusions: Two doses of BNT162b2 and mRNA-1273 vaccines are highly effective against both symptomatic infection and severe outcomes. Effectiveness is lower after only a single dose, particularly for older adults shortly after the first dose.

mRNA Vaccine Effectiveness against COVID-19 among Symptomatic Outpatients Aged ≥16 Years in the United States, February – May 2021

“…During February-May 2021 in a multisite outpatient network evaluating COVID-19 vaccine effectiveness, vaccination reduced laboratory-confirmed symptomatic illness by 91% among those fully vaccinated and 75% among those partially vaccinated. These findings add to evidence from clinical trials of efficacy against symptomatic illness and from observational studies of vaccine effectiveness across the continuum of illness severity in multiple countries [1][2][3][4][5][10][11][12].…”

Single-dose mRNA vaccine effectiveness against SARS-CoV-2, including P.1 and B.1.1.7 variants: a test-negative design in adults 70 years and older in British Columbia, Canada

“…Because the PLOVER database from which we sampled does not reliably capture symptoms or onset dates, we assessed VE against any infection without symptom or severity specification. VE estimates against more severe outcomes are anticipated to be higher than we report for infection per se [15][16][17]. Finally, we were limited in our ability to assess VE over the long-term or to compare to younger age groups prioritized later for vaccination, but those analyses are underway.…”

“…Using the TND to assess VE among adults ≥70 years in England (but including care-home residents), Bernal et al reported single-dose mRNA VE against symptomatic SARS-CoV-2 infection reaching 61% (95% CI 51-69) by 28-34 days[15], similar to our estimate of 69% (95% CI 59-77) by the same interval. In a matched case-control study of adults 80-83-years-old in England (excluding care-home residents), Mason ≥14 days between vaccination and specimen collection[17]. In sub-analysis of adults ≥70 years (excluding care-home residents), authors report VE of 40% (95% CI 29-49) which is lower than…”

“…Includes mRNA vaccine receipt only; viral vector vaccine recipients excluded. Percentage vaccinated among SARS-CoV-2 test-positive cases and test-negative controls and case tallies by epidemiological week, participating adults ≥70 years of age, British Columbia, Canada, weeks 14-17 Figure2Adjusted vaccine effectiveness estimates by interval in days since vaccination and restricted by sub-group, adults ≥70 years of age, British Columbia, Canada, weeks[14][15][16][17]…”

Waning COVID-19 vaccine effectiveness in Japan

“…Vaccine efficacy was estimated as 95% through clinical trials (25). In the real world, it was also estimated as 46-80% for the first dose and 86-90% for the second dose (26)(27)(28)(29)(30)(31) through case-control studies or test-negative design. However, even in the real world, such studies specifically examine protection for vaccine recipients only and ignore herd immunity, representing vaccine effects on non-vaccine recipients.…”