SARS-CoV-2 Infection Risk by Vaccine Doses and Prior Infections Over 24 Months: ProHEpiC-19 Longitudinal Study
Journal
JMIR Public Health and Surveillance
ISSN
2369-2960
Date Issued
2024-11-22
Author(s)
Pere Torán-Monserrat
Noemí Lamonja-Vicente
Anna Costa-Garrido
Lucía A Carrasco-Ribelles
Bibiana Quirant
Marc Boigues
Carla Chacón
Rosalia Dacosta-Aguayo
Fernando Arméstar
Eva María Martínez Cáceres
Julia G Prado
Concepción Violán
Type
journal-article
Abstract
<jats:title>Abstract</jats:title>
<jats:sec sec-type="background">
<jats:title>Background</jats:title>
<jats:p>As the vaccination campaign against COVID-19 progresses, it becomes crucial to comprehend the lasting effects of vaccination on safeguarding against new infections or reinfections.</jats:p>
</jats:sec>
<jats:sec sec-type="objective">
<jats:title>Objective</jats:title>
<jats:p>This study aimed to assess the risk of new SARS-CoV-2 infections based on the number of vaccine doses, prior infections, and other clinical characteristics.</jats:p>
</jats:sec>
<jats:sec sec-type="methods">
<jats:title>Methods</jats:title>
<jats:p>We defined a cohort of 800 health care workers in a 24-month study (March 2020 to December 2022) in northern Barcelona to determine new infections by SARS-CoV-2. We used extended Cox models, specifically Andersen-Gill (AG) and Prentice-Williams-Peterson, and we examined the risk of new infections. The AG model incorporated variables such as sex, age, job title, number of chronic conditions, vaccine doses, and prior infections. Additionally, 2 Prentice-Williams-Peterson models were adjusted, one for those individuals with no or 1 infection and another for those with 2 or 3 infections, both with the same covariates as the AG model.</jats:p>
</jats:sec>
<jats:sec sec-type="results">
<jats:title>Results</jats:title>
<jats:p>The 800 participants (n=605, 75.6% women) received 1, 2, 3, and 4 doses of the vaccine. Compared to those who were unvaccinated, the number of vaccine doses significantly reduced (<jats:italic>P</jats:italic><.001) the risk of infection by 66%, 81%, 89%, and 99%, respectively. Unit increase in the number of prior infections reduced the risk of infection by 75% (<jats:italic>P</jats:italic><.001). When separating individuals by number of previous infections, risk was significantly reduced for those with no or 1 infection by 61% (<jats:italic>P</jats:italic>=.02), and by 88%, 93%, and 99% (<jats:italic>P</jats:italic><.001) with 1, 2, 3, or 4 doses, respectively. In contrast, for those with 2 or 3 previous infections, the reduction was only significant with the fourth dose, at 98% (<jats:italic>P</jats:italic><.001). The number of chronic diseases only increased the risk by 28%‐31% (<jats:italic>P</jats:italic><.001) for individuals with 0‐1 previous infections.</jats:p>
</jats:sec>
<jats:sec sec-type="conclusions">
<jats:title>Conclusions</jats:title>
<jats:p>The study suggests that both prior infections and vaccination status significantly contribute to SARS-CoV-2 immunity, supporting vaccine effectiveness in reducing risk of reinfection for up to 24 months after follow-up from the onset of the pandemic. These insights contribute to our understanding of long-term immunity dynamics and inform strategies for mitigating the impact of COVID-19.</jats:p>
</jats:sec>
<jats:sec sec-type="background">
<jats:title>Background</jats:title>
<jats:p>As the vaccination campaign against COVID-19 progresses, it becomes crucial to comprehend the lasting effects of vaccination on safeguarding against new infections or reinfections.</jats:p>
</jats:sec>
<jats:sec sec-type="objective">
<jats:title>Objective</jats:title>
<jats:p>This study aimed to assess the risk of new SARS-CoV-2 infections based on the number of vaccine doses, prior infections, and other clinical characteristics.</jats:p>
</jats:sec>
<jats:sec sec-type="methods">
<jats:title>Methods</jats:title>
<jats:p>We defined a cohort of 800 health care workers in a 24-month study (March 2020 to December 2022) in northern Barcelona to determine new infections by SARS-CoV-2. We used extended Cox models, specifically Andersen-Gill (AG) and Prentice-Williams-Peterson, and we examined the risk of new infections. The AG model incorporated variables such as sex, age, job title, number of chronic conditions, vaccine doses, and prior infections. Additionally, 2 Prentice-Williams-Peterson models were adjusted, one for those individuals with no or 1 infection and another for those with 2 or 3 infections, both with the same covariates as the AG model.</jats:p>
</jats:sec>
<jats:sec sec-type="results">
<jats:title>Results</jats:title>
<jats:p>The 800 participants (n=605, 75.6% women) received 1, 2, 3, and 4 doses of the vaccine. Compared to those who were unvaccinated, the number of vaccine doses significantly reduced (<jats:italic>P</jats:italic><.001) the risk of infection by 66%, 81%, 89%, and 99%, respectively. Unit increase in the number of prior infections reduced the risk of infection by 75% (<jats:italic>P</jats:italic><.001). When separating individuals by number of previous infections, risk was significantly reduced for those with no or 1 infection by 61% (<jats:italic>P</jats:italic>=.02), and by 88%, 93%, and 99% (<jats:italic>P</jats:italic><.001) with 1, 2, 3, or 4 doses, respectively. In contrast, for those with 2 or 3 previous infections, the reduction was only significant with the fourth dose, at 98% (<jats:italic>P</jats:italic><.001). The number of chronic diseases only increased the risk by 28%‐31% (<jats:italic>P</jats:italic><.001) for individuals with 0‐1 previous infections.</jats:p>
</jats:sec>
<jats:sec sec-type="conclusions">
<jats:title>Conclusions</jats:title>
<jats:p>The study suggests that both prior infections and vaccination status significantly contribute to SARS-CoV-2 immunity, supporting vaccine effectiveness in reducing risk of reinfection for up to 24 months after follow-up from the onset of the pandemic. These insights contribute to our understanding of long-term immunity dynamics and inform strategies for mitigating the impact of COVID-19.</jats:p>
</jats:sec>
Subjects
cohort
;
coronavirus
;
covid-19
;
epidemiological
;
epidemiology
;
extended cox models
;
health care workers
;
infectious
;
longitudinal
;
respiratory
;
risks
;
sars-cov-2
;
vaccinated
;
vaccination
;
vaccines
;
adult
;
covid-19
;
covid-19 vaccines
;
female
;
health personnel
;
humans
;
longitudinal studies
;
male
;
middle aged
;
sars-cov-2
;
spain
;
vaccination
;
sars-cov-2 vaccine
;
adult
;
coronavirus disease 2019
;
epidemiology
;
female
;
health care personnel
;
human
;
longitudinal study
;
male
;
middle aged
;
prevention and control
;
severe acute respiratory syndrome coronavirus 2
;
spain
;
vaccination