Sara Carazo1, Denis Talbot1,2, Nicole Boulianne3, Marc Brisson1,2,4, Rodica Gilca1,2,3, Geneviève Deceuninck1, Nicholas Brousseau1,2,3, Mélanie Drolet1, Manale Ouakki3, Chantal Sauvageau1,2,3, Sapha Barkati5,6, Élise Fortin3, Alex Carignan7, Philippe De Wals2,3, Danuta M Skowronski8, Gaston De Serres1,2,3. 1. Centre de recherche du Centre Hospitalier Universitaire de Québec-Universite Laval, Québec City, Québec, Canada. 2. Social and Preventive Medicine Department, Laval University, Québec City, Québec, Canada. 3. Biological and Occupational Risks, Institut national de sante publique du Québec, Québec City, Québec, Canada. 4. Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom. 5. JD MacLean Centre for Tropical Diseases, McGill University, Montreal, Québec, Canada. 6. Department of Medicine, Division of Infectious Diseases, McGill University, Montreal, Québec, Canada. 7. Department of Microbiology and Infectious Diseases, Sherbrooke University, Sherbrooke, Québec, Canada. 8. Communicable Diseases and Immunization Services, BC Centre for Disease Control, Vancouver, British Columbia, Canada.
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 (10:1), 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.
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 (10:1), 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.
Authors: Melissa M Higdon; Brian Wahl; Carli B Jones; Joseph G Rosen; Shaun A Truelove; Anurima Baidya; Anjalika A Nande; Parisa A ShamaeiZadeh; Karoline K Walter; Daniel R Feikin; Minal K Patel; Maria Deloria Knoll; Alison L Hill Journal: Open Forum Infect Dis Date: 2022-04-18 Impact factor: 4.423
Authors: Amit Kaura; Adam Trickey; Anoop S V Shah; Umberto Benedetto; Ben Glampson; Abdulrahim Mulla; Luca Mercuri; Sanjay Gautama; Ceire E Costelloe; Ian Goodman; Julian Redhead; Kavitha Saravanakumar; Erik Mayer; Jamil Mayet Journal: EClinicalMedicine Date: 2022-03-12