Big, real-world study confirms Covid-19 shots provide much more protection than natural immunity, especially against death

Vaccines give significantly more protection than natural immunity against Covid-19, especially against death, according to one of the first large, real-world studies comparing the two forms of immunity.

The study found that to be true of all age groups in protecting against death, hospitalizations and emergency department visits. "The lower death rate of vaccinated individuals was especially impressive for adults ages 60 years or older," said a press release from the Regenstrief Institute at the Indiana University School of Medicine and the Vanderbilt University Medical Center, which did the study.

“The data raises questions about the wisdom of reliance on natural immunity when safe and effective vaccines are available,” the release said.

Vaccinated people had a higher rate of Covid infection than individuals previously infected (6.7% to 2.9%), but the vaccines “protected against severe disease while natural immunity did not confer the same benefit,” said Dr. Shaun Grannis, the study's corresponding author and vice president for data and analysis at the Regenstrief Institute. 

The release said, "The all-cause death and hospital-admission rates for vaccinated individuals were 37 percent lower than the rates for those with natural immunity acquired from previous Covid infection. The rate of ED visits for all causes was 24 percent lower for vaccinated individuals than for the previously infected."

Gannis said, “This large population study of the entire state of Indiana should encourage individuals everywhere to get themselves and their children vaccinated and not rely on natural immunity. As vaccinated individuals were more likely to actually get Covid than those with natural immunity, the lower death rate of vaccine recipients who develop Covid appears to be due to vaccination and not to a tendency for risk-averse behaviors, such as mask-wearing, hand sanitizing and social distancing.”

The study analyzed data on pairs of vaccine recipients and people with prior infections, matched by age, sex, dates of initial exposure to the vaccines or the virus itself, and Covid risk scores as defined by the U.S. Centers for Disease Control and Prevention. The data came from the Indiana Network for Patient Care, one of the nation’s largest health information exchanges, as well as death reports from the State of Indiana, the release said.

The study is important because previous studies didn't look at emergency-department visits, hospitalizations and mortality for non-Covid reasons, said its first author, Regenstrief Institute Research Scientist Wanzhu Tu, Ph.D. “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.”

The study, SARS-CoV-2 infection, hospitalization and death in vaccinated and infected individuals in Indiana USA, November 2020 - February 2022, is published in the American Journal of Public Health.