A recent study conducted across 187 hospitals, announced by the CDC on Friday, has good news for the fully vaccinated and bad news for those who have been pushing the notion that previous infection alone will bring the population to herd immunity.

The study, published in the Morbidity and Mortality Weekly Report of the U.S. Department of Health and Human Services, found that vaccination is five times more effective than previous infection in preventing COVID-19.

The CDC wrote in its press release on last Friday, October 29:

Today, CDC published new science reinforcing that vaccination is the best protection against COVID-19. In a new MMWR examining more than 7,000 people across 9 states who were hospitalized with COVID-like illness, CDC found that those who were unvaccinated and had a recent infection were 5 times more likely to have COVID-19 than those who were recently fully vaccinated and did not have a prior infection.

The data demonstrate that vaccination can provide a higher, more robust, and more consistent level of immunity to protect people from hospitalization for COVID-19 than infection alone for at least 6 months.

“We now have additional evidence that reaffirms the importance of COVID-19 vaccines, even if you have had prior infection. 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,” said CDC Director Dr. Rochelle P. Walensky.

The study’s summary, in a section entitled “What is added by this report?” stated:

Among COVID-19–like illness hospitalizations among adults aged ≥18 years whose previous infection or vaccination occurred 90–179 days earlier, the adjusted odds of laboratory-confirmed COVID-19 among unvaccinated adults with previous SARS-CoV-2 infection were 5.49-fold higher than the odds among fully vaccinated recipients of an mRNA COVID-19 vaccine who had no previous documented infection (95% confidence interval = 2.75–10.99).