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.
Keywords: COVID-19; SARS-CoV-2; healthcare workers; test-negative design; vaccine effectiveness.
【저자키워드】 COVID-19, SARS-CoV-2, Healthcare workers, vaccine effectiveness, test-negative design, 【초록키워드】 Stratification, public health, Vaccine, coronavirus, vaccination, Healthcare workers, Hospitalization, mRNA vaccine, VoC, SARS-COV-2 infection, severity, variants of concern, outcome, severe acute respiratory syndrome Coronavirus, immunization, variants, healthcare worker, stability, Surveillance, HCWs, mRNA, healthcare, hospitalizations, VOCs, Patient, Effectiveness, Logistic regression, Alpha, Canada, Analysis, dose, Contact, Single-dose, HCW, determined by, specimen collection, Messenger RNA, acute respiratory syndrome, 95% CI, acute respiratory syndrome coronavirus, acute respiratory syndrome coronavirus 2, 95% confidence interval, recipients, second dose, specimen, primary analysis, illness onset, recipient, postvaccination, controls, likelihood, Randomly, defined, provided, sustained, 【제목키워드】 coronavirus 2, RNA, respiratory, worker, messenger, Against, Week,