The Impact of Vaccination on Severity of Illness in COVID-19

With the FDA's emergency use authorization declaration in December of 2020, the Pfizer-BioNtech vaccine became the first of several vaccines to kick off the mass vaccination effort across the United States against CoronaVIrus Disease 2019 (COVID-19). Subsequently, Moderna as well as Johnson and Johnson both had vaccines receive emergency use authorization. While the Pfizer and the Moderna vaccines both utilize novel mRNA technology, Johnson and Johnson's vaccine uses a viral vector that has been used previously in both the approved European Ebola vaccine and a trial vaccine for HIV. However, none of these vaccine types have previously been approved in the United States. While preliminary data from safety and efficacy trials have shown positive results, actual-world data on its effectiveness is still lacking. Several small cohort studies and one large trial from Israel are currently the only insights into the actual rates of infection, hospitalization, and severe illness among vaccinated individuals. As COVID-19 variants, with the potential to reduce vaccine efficacy, continue to emerge worldwide, there is a need of more data regarding the real-world effectiveness of our current mass vaccination efforts. Vaccination efforts in the State of Michigan have been ongoing since December 2020. Given that approximately 33.7% of the state's population is either partially or fully vaccinated, it is unclear why the number of cases has risen so dramatically or if immunization efforts can help the situation. Given the current situation in the State of Michigan, this study will evaluate the efficacy of COVID-19 vaccination on rates of hospital visits and severe illness when breakthrough Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2) infection occurs in a region with high incidence of variant strain disease.