COVID-19 vaccines protect against more than just COVID: study

COVID-19 vaccination confers much greater protection against individuals being hospitalized or rushed to emergency departments for any cause—not just COVID-19 infection—compared to individuals who’ve been previously infected by the disease but not vaccinated against it, according to a new study.

Researchers with the Regenstrief Institute, the Indiana University School of Medicine and the Vanderbilt University Medical Center found that all-cause death and hospital admission rates for vaccinated individuals are 37% lower than for those who’ve been previously infected by COVID-19 but had not been vaccinated. In addition, the rates of ED admissions for vaccinated individuals for all causes is 24% lower for the vaccinated than the unvaccinated, according to the study published in the American Journal of Public Health.

Perhaps counterintuitively, the study also finds that vaccinated individuals are more likely to become infected by COVID-19 than unvaccinated individuals. Incidence of COVID-19 infection is 6.7% for the vaccinated as compared to 2.9% of those who’d not gotten vaccinated but had prior infections, although vaccination better protected against severe SARS-CoV-2 infection than prior infection, according to the study.

Corresponding author Shaun Grannis, M.D., vice president for data and analytics at the Regenstrief Institute, tells Fierce Healthcare that the study does not include the period when the bivalent vaccine became available. In addition, he says, “mitigation factors may have played a role, but that was not measured in this study.”

The study offers several explanations for why individuals who’d been vaccinated appeared to be less protected against COVID-19 infection than those who’d had prior infection.

“Although our results suggest that natural immunity provides greater protection against subsequent infections than vaccines, residual confounding attributable to health-seeking behavior may still have an impact on these results. If the rate of symptomatic testing for SARS-CoV-2 infection is greater among vaccinated individuals (a quantity unmeasured in our study), vaccine effectiveness would be underestimated.”

The study also suggests that the fact that those with previous infection were less likely to get infected by COVID-19 indicates mitigation measures such as masking, hand washing and social distancing—while still important—aren’t the reason those who’ve gotten vaccinated had lower rates of all-cause hospitalization and death.

The matched cohort study looks at data from the state of Indiana from 267,847 individuals who’d received vaccines and those who hadn’t between the ages of 12 and 110 years from the Indiana Network for Patient Care (INPC) database. Data were examined for anybody in this population who’d had at least one previous encounter with the 38 health systems representing 117 hospitals and 18,486 physician practices monitored by the INPC between Jan. 1, 2016 and Feb. 9, 2022.

The study “has important public health implications as previous studies investigated COVID-specific ED visits, hospitalizations and mortality but didn’t capture the non-COVID related ones," Regenstrief Institute research scientist Wanzhu Tu, Ph.D., said in a press release. "Our work confirms that mRNA vaccines have kept people out of the ED and the hospital as well as lowered the likelihood of death from any cause. And we saw this pattern in every age group.”