CDC: Study shows COVID-19 vaccines offer better protection than prior infection
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New study data show that vaccination offers better protection against COVID-19 than prior infection, the CDC said Friday.
The data are from a study published in MMWR that included more than 200 previously infected Kentucky residents. Study participants who were unvaccinated were 2.34 times more likely to be reinfected with SARS-CoV-2, researchers reported.
“If you have had COVID-19 before, please still get vaccinated,” CDC Director Rochelle Walensky, MD, MPH, said in a statement. “This study shows you are twice as likely to get infected again if you are unvaccinated. Getting the vaccine is the best way to protect yourself and others around you, especially as the more contagious delta variant spreads around the country.”
In the study, Alyson M. Cavanaugh, PhD, DPT, MPH, a CDC Epidemic Intelligence Service officer embedded with the Kentucky Department for Public Health, and colleagues assessed reinfections among Kentucky residents aged 18 years or older who had an initial case between March to December 2020 and a subsequent positive test in May or June of this year. They included a control group of people who were not reinfected in that time period.
Overall, there were 246 case patients included in the study and 492 patients in the control group. Among the case patients, 20.3% were fully vaccinated compared with 34.3% of those in the control group, showing that the unvaccinated participants were more likely to become reinfected compared with people who were fully vaccinated (OR, 2.34; 95% CI, 1.58-3.47).
Participants who were partially vaccinated were 1.56 more likely to become reinfected (95% CI, 0.81-3.01).
“All eligible persons should be offered vaccination, including those with previous SARS-CoV-2 infection, to reduce their risk for future infection,” Cavanaugh and colleagues wrote.
Perspective
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The study illustrates the fact that prior immunity, though significant, is not as robust against preventing reinfection than vaccine-induced immunity. It’s important to understand that this study does not address whether people with prior infection were protected against severe infection, which they likely were because of their immune status. It’s also important to highlight the fact that partial vaccination was statistically not different than people who are fully vaccinated in those with prior immunity. This finding — coupled with others — should inform guideline developers to consider advocating only a single dose of two-dose vaccine regimens for those with prior infections.
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