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Risk of COVID-19 Reinfection and Vaccine Breakthrough Infection, Madera County, California, 2021

Nguyen, Minhphuong and Paul, Eric and Mills, Paul K. and Paul, Simon (2022) Risk of COVID-19 Reinfection and Vaccine Breakthrough Infection, Madera County, California, 2021. . (Unpublished)

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The probability of either testing COVID-19 positive or dying for three cohorts in Madera County, California in 2021 was compared. These cohorts included 1. those unvaccinated, 2. those vaccinated and 3. persons with a previous COVID-19 infection. The three groups were made generally comparable by matching on age, gender, postal zip code of residence, and the date of either COVID-19 infection or of vaccination. The hazard ratio (HR) for death (from all causes) after COVID-19 infection vs. vaccination was 11.7 (95% CI 5.91-23.1, p14 days after initial COVID-19 infection or after completing primary COVID-19 vaccination was 1.98 (95% CI 1.53-2.58 p<0.001). As the majority of positive COVID-19 tests in the post COVID-19 cohort occurred within 90 days of the initial infection, and as these early positives may not represent a new infection, we also compared rates of testing COVID-19 positive 90 days after initial infection or vaccination. After removing these early positive COVID-19 tests that occurred between days 14-90, the HR ratio for testing COVID-19 positive is now lower for the post COVID-19 cohort compared with the vaccinated cohort. The risk for having a positive COVID-19 test occurring 90 days after an initial COVID-19 infection or after vaccination was 0.54 (95% CI 0.33-0.87, p<0.05) for the post COVID-19 group vs Vaccinated group. Thus the risk for testing COVID-19 positive was higher in the first 90 days after COVID-19 infection compared to those vaccinated. However, from 90 to 300 days after COVID-19 infection, the post COVID-19 infection cohort had a lower risk of testing COVID-19 positive than those fully vaccinated.

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Additional Information:The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license. This study did not receive any funding. All data produced in the present work are contained in the manuscript The authors have declared no competing interest. Author Declarations: I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes. The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was reviewed by the County of Fresno, Department of Public Health Institutional Review Board, and was approved on January 20, 2022. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes. I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes. I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes.
Record Number:CaltechAUTHORS:20220124-214548000
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Official Citation:Risk of COVID-19 Reinfection and Vaccine Breakthrough Infection, Madera County, California, 2021 Minhphuong Nguyen, Eric Paul, Paul K. Mills, Simon Paul medRxiv 2022.01.22.22269105; doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113083
Deposited By: George Porter
Deposited On:25 Jan 2022 15:04
Last Modified:25 Jan 2022 15:04

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