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Time-varying effects of COVID-19 vaccination on symptomatic and asymptomatic infections in a prospective university cohort in the USA
Journal article   Open access   Peer reviewed

Time-varying effects of COVID-19 vaccination on symptomatic and asymptomatic infections in a prospective university cohort in the USA

Lucy Robinson, Anna Feting, Isamu Isozaki, Vicki Seyfert-Morgolis, Mitchell Jay, Edward Kim and Charles Cairns
BMJ open, v 15(2), e084408
22 Feb 2025
DOI: https://doi.org/10.1136/bmjopen-2024-084408
PMID: 39987006
Featured in Collection :   UN Sustainable Development Goals @ Drexel
url
https://doi.org/10.1136/bmjopen-2024-084408View
Published, Version of Record (VoR) Open

Abstract

Adult Asymptomatic Infections - epidemiology COVID-19 - epidemiology COVID-19 - prevention & control COVID-19 Testing COVID-19 Vaccines - administration & dosage Female Humans Male Middle Aged Prospective Studies SARS-CoV-2 - immunology Time Factors United States - epidemiology Universities Vaccination - statistics & numerical data Vaccine Efficacy Young Adult
Despite widespread vaccination programmes and consensus recommendations, the understanding of the durability of COVID-19 vaccination against ensuing infection and transmission at the individual level is incomplete. The objective of this study was to estimate the effects of time-varying covariates including time since vaccination and symptoms on subsequent positive SARS-CoV-2 test results and assess the stability of these effects between March 2020 and April 2022. Prospective cohort study. Urban university in the USA. Drexel University students, faculty, and staff (n=15 527) undergoing mandatory COVID-19 symptom tracking, testing and vaccinations. Systematic symptom tracking and SARS-COV-2 testing starting in September 2020 and mandatory COVID-19 vaccination starting in September 2021. COVID-19 vaccine effectiveness modified by time since vaccination and symptoms. Using fit-for-purpose digitally based symptom and vaccine tracking and mandatory comprehensive testing for SARS-CoV-2 infection, we estimate the time-dependent effects of vaccination, symptoms and covariates on the risk of infection with a Cox proportional hazards model based on calendar time scale. We found a strong protective effect of vaccination against symptomatic infection. However, there was strong evidence of a protective effect against infection only in the first 90 days after completed vaccination, and only against symptomatic versus asymptomatic infection. The overall estimated effect of vaccination within 30 days, including asymptomatic infections, was 37.3% (95% CI 26%, 47%). Vaccine effect modification by reported symptoms and time period was estimated, revealing the protective effect of vaccination within 90 days against symptomatic infection that varied from 90% (95% CI 84%, 94%) to 49%(95% CI -77%, 85%) across time periods. This study is among the first to prospectively capture complete COVID-19 symptom, testing and vaccination data over a multiyear period. Overall effectiveness of the COVID-19 vaccine against subsequent infection, including transmissible asymptomatic infections, is modest and wanes after 90 days. Vaccination policies may need to take these issues into account.

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3 citations in Web of Science
1 citations in Scopus

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UN Sustainable Development Goals (SDGs)

This publication has contributed to the advancement of the following goals:

#3 Good Health and Well-Being

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Web of Science research areas
Medicine, General & Internal
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