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. 2023 Mar 1;17(3):e13104. doi: 10.1111/irv.13104

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© 2023 The Authors. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.

This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Effectiveness of a second booster dose of COVID‐19 mRNA vaccine against laboratory‐confirmed symptomatic SARS‐CoV‐2 infection relative to single booster receipt among adults ≥50 years of age: Prospective Assessment of COVID‐19 in a Community (PACC) study March 29, 2022–July 28, 2022. Abbreviations: mRNA, messenger RNA; VE, vaccine effectiveness. ^aRelative vaccine effectiveness from Cox proportional hazards regression models predicting the hazard SARS‐CoV‐2 infection by time‐varying vaccination status adjusted for age and evidence of SARS‐CoV‐2 infection prior to person‐time entry. Vaccine effectiveness calculated as 100* (one minus the adjusted hazard ratio). ^bSecond booster (4th) dose received ≥14 days ago. ^cFirst booster (3rd) dose received ≥4 months ago.