Dataset Information

Estimating COVID-19 Vaccination and Booster Effectiveness Using Electronic Health Records from an Academic Medical Center in Michigan

ABSTRACT:

Introduction

Observational studies of COVID-19 vaccines' effectiveness can provide crucial information regarding the strength and durability of protection against SARS-CoV-2 infection, and whether the protective response varies across different patient subpopulations and in the context of different SARS-CoV-2 variants.

Methods

We used a test negative study design to assess vaccine effectiveness against SARS-CoV-2 infection and severe COVID-19 resulting in hospitalization, intensive care unit admission, or death using electronic health records data of 170,741 adults who had been tested for COVID-19 at the University of Michigan Medical Center between January 1 and December 31, 2021. We estimated vaccine effectiveness by comparing the odds of vaccination between cases and controls during each 2021 calendar quarter, and stratified all outcomes by vaccine type, patient demographic and clinical characteristics, and booster status.

Results

Unvaccinated individuals had more than double the rate of infections (12.1% vs. 4.7%) and more than three times the rate of severe COVID-19 outcomes (1.4% vs. 0.4%) compared to vaccinated individuals. COVID-19 vaccines were 62.1% (95% CI 60.3–63.8%) effective against a new infection, with protection waning in the last two quarters of 2021. The VE against severe disease overall was 73.7% (69.6–77.3%) and remained high throughout 2021. Data from the last quarter of 2021 indicated that adding a booster dose augmented effectiveness against infection up to 87.3% (85.0–89.2%) and against severe outcomes up to 94.0% (89.5–96.6%). Pfizer-BioNTech and Moderna vaccines showed comparable performance when controlling for vaccination timing. VE was greater in more socioeconomically affluent areas and among health care workers; otherwise, we did not detect any significant modification of VE by covariates including gender, race, and socioeconomic status.

Conclusions

COVID-19 vaccines were highly protective against infection and severe COVID-19 resulting in hospitalization, ICU admission, or death. Administration of a booster dose significantly increased vaccine effectiveness against both outcomes. Ongoing surveillance is required to assess durability of these findings.

SUBMITTER: Roberts E

PROVIDER: S-EPMC9323299 | biostudies-literature |

REPOSITORIES: biostudies-literature

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