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Single-Dose Messenger RNA Vaccine Effectiveness Against Severe Acute Respiratory Syndrome Coronavirus 2 in Healthcare Workers Extending 16 Weeks Postvaccination: A Test-Negative Design From Québec, Canada.
Carazo, Sara; Talbot, Denis; Boulianne, Nicole; Brisson, Marc; Gilca, Rodica; Deceuninck, Geneviève; Brousseau, Nicholas; Drolet, Mélanie; Ouakki, Manale; Sauvageau, Chantal; Barkati, Sapha; Fortin, Élise; Carignan, Alex; De Wals, Philippe; Skowronski, Danuta M; De Serres, Gaston.
  • Carazo S; Centre de recherche du Centre Hospitalier Universitaire de Québec-Universite Laval, Québec City, Québec, Canada.
  • Talbot D; Centre de recherche du Centre Hospitalier Universitaire de Québec-Universite Laval, Québec City, Québec, Canada.
  • Boulianne N; Social and Preventive Medicine Department, Laval University, Québec City, Québec, Canada.
  • Brisson M; Biological and Occupational Risks, Institut national de sante publique du Québec, Québec City, Québec, Canada.
  • Gilca R; Centre de recherche du Centre Hospitalier Universitaire de Québec-Universite Laval, Québec City, Québec, Canada.
  • Deceuninck G; Social and Preventive Medicine Department, Laval University, Québec City, Québec, Canada.
  • Brousseau N; Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom.
  • Drolet M; Centre de recherche du Centre Hospitalier Universitaire de Québec-Universite Laval, Québec City, Québec, Canada.
  • Ouakki M; Social and Preventive Medicine Department, Laval University, Québec City, Québec, Canada.
  • Sauvageau C; Biological and Occupational Risks, Institut national de sante publique du Québec, Québec City, Québec, Canada.
  • Barkati S; Centre de recherche du Centre Hospitalier Universitaire de Québec-Universite Laval, Québec City, Québec, Canada.
  • Fortin É; Centre de recherche du Centre Hospitalier Universitaire de Québec-Universite Laval, Québec City, Québec, Canada.
  • Carignan A; Social and Preventive Medicine Department, Laval University, Québec City, Québec, Canada.
  • De Wals P; Biological and Occupational Risks, Institut national de sante publique du Québec, Québec City, Québec, Canada.
  • Skowronski DM; Centre de recherche du Centre Hospitalier Universitaire de Québec-Universite Laval, Québec City, Québec, Canada.
  • De Serres G; Biological and Occupational Risks, Institut national de sante publique du Québec, Québec City, Québec, Canada.
Clin Infect Dis ; 75(1): e805-e813, 2022 Aug 24.
Article in English | MEDLINE | ID: covidwho-1708191
ABSTRACT

BACKGROUND:

In Canada, first and second doses of messenger RNA (mRNA) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were uniquely spaced 16 weeks apart. We estimated 1- and 2-dose mRNA vaccine effectiveness (VE) among healthcare workers (HCWs) in Québec, Canada, including protection against varying outcome severity, variants of concern (VOCs), and the stability of single-dose protection up to 16 weeks postvaccination.

METHODS:

A test-negative design compared vaccination among SARS-CoV-2 test-positive and weekly matched (101), randomly sampled, test-negative HCWs using linked surveillance and immunization databases. Vaccine status was defined by 1 dose ≥14 days or 2 doses ≥7 days before illness onset or specimen collection. Adjusted VE was estimated by conditional logistic regression.

RESULTS:

Primary analysis included 5316 cases and 53 160 controls. Single-dose VE was 70% (95% confidence interval [CI], 68%-73%) against SARS-CoV-2 infection; 73% (95% CI, 71%-75%) against illness; and 97% (95% CI, 92%-99%) against hospitalization. Two-dose VE was 86% (95% CI, 81%-90%) and 93% (95% CI, 89%-95%), respectively, with no hospitalizations. VE was higher for non-VOCs than VOCs (73% Alpha) among single-dose recipients but not 2-dose recipients. Across 16 weeks, no decline in single-dose VE was observed, with appropriate stratification based upon prioritized vaccination determined by higher vs lower likelihood of direct patient contact.

CONCLUSIONS:

One mRNA vaccine dose provided substantial and sustained protection to HCWs extending at least 4 months postvaccination. In circumstances of vaccine shortage, delaying the second dose may be a pertinent public health strategy.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: SARS-CoV-2 / COVID-19 Type of study: Experimental Studies / Observational study / Prognostic study / Randomized controlled trials Topics: Vaccines / Variants Limits: Humans Country/Region as subject: North America Language: English Journal: Clin Infect Dis Journal subject: Communicable Diseases Year: 2022 Document Type: Article Affiliation country: Cid

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Full text: Available Collection: International databases Database: MEDLINE Main subject: SARS-CoV-2 / COVID-19 Type of study: Experimental Studies / Observational study / Prognostic study / Randomized controlled trials Topics: Vaccines / Variants Limits: Humans Country/Region as subject: North America Language: English Journal: Clin Infect Dis Journal subject: Communicable Diseases Year: 2022 Document Type: Article Affiliation country: Cid