A new study from the Centers for Disease Control and Prevention (CDC) suggests that vaccination is much more effective at protecting people against COVID-19 infection than immunity from previous infection from the coronavirus.

What You Need To Know

  • A new CDC study study found that people who were not vaccinated and were previously infected with COVID-19 were 5.49 times more likely to test positive for the coronavirus than people who were vaccinated within the last 3-6 months

  • The study suggests that vaccination is much more effective at protecting people against COVID-19 infection than immunity from previous infection from the coronavirus

  • "We now have additional evidence that reaffirms the importance of COVID-19 vaccines, even if you have had prior infection," CDC Director Dr. Rochelle Walensky said in a statement

  • The study comes amid arguments that immunity from prior COVID-19 infection provides suitable protection against the coronavirus, which health experts have roundly disputed

The study, which was published Friday in the CDC's Morbidity and Mortality Weekly Report (MMWR), looked at 7,000 people in 187 hospitals across nine states from Jan. to Sept. of 2021. 

The study found that people who were not vaccinated and were previously infected with COVID-19 were 5.49 times more likely to test positive for the coronavirus than people who were vaccinated within the last 3-6 months.

"We now have additional evidence that reaffirms the importance of COVID-19 vaccines, even if you have had prior infection," CDC Director Dr. Rochelle Walensky said in a statement. "This study adds more to the body of knowledge demonstrating the protection of vaccines against severe disease from COVID-19."

"The best way to stop COVID-19, including the emergence of variants, is with widespread COVID-19 vaccination and with disease prevention actions such as mask wearing, washing hands often, physical distancing, and staying home when sick," she added.

The study comes amid arguments that immunity from prior COVID-19 infection provides suitable protection against the coronavirus, which health experts have roundly disputed. The researchers behind the study suggested that these findings should put that matter to rest, urging everyone who is eligible to get vaccinated, including those previously infected with COVID-19.

"All eligible persons should be vaccinated against COVID-19 as soon as possible, including unvaccinated persons previously infected with SARS-CoV-2," the researchers wrote.

The CDC acknowledged a number of limitations in the study, including an Israeli study from earlier this year which found the opposite results. However, that study looked at people who were vaccinated six months ago or longer.

"In this study, the benefit of vaccination compared with infection without vaccination appeared to be higher for recipients of Moderna than Pfizer-BioNTech vaccine, which is consistent with a recent study that found higher vaccine effectiveness against COVID-19 hospitalizations for Moderna vaccine recipients than for Pfizer-BioNTech vaccine recipients," researchers wrote. (Researchers did not include those vaccinated with the single-shot Johnson & Johnson vaccine.)

They also acknowledged that they only included hospitalized patients in the study, and compared groups with two different kinds of immunity – vaccine-based vs. natural infection based-immunity – but it appears from the study that vaccination can provide a more robust, higher and more consistent level of immunity.

"Understanding infection-induced and vaccine-induced immunity over time is important, particularly for future studies to consider," researchers wrote.