Natural immunity is good. Getting vaccinated after being sick with COVID-19 is better. - USA TODAY

As with most illnesses, contracting COVID-19 provides immune "memory" that helps protect against a future infection.

Getting vaccinated three months – or even better, six months – after infection provides the best possible protection, she said.

In a new study from the Rockefeller Institute in New York, researchers found that people who get vaccinated after catching COVID-19 may be protected against a wider range of variants than people who get vaccinated alone.

"At five-six months post-vaccination or infection," she said, "the vaccinated participants had overall higher levels of neutralizing antibodies than the infected, including against variants.".

But among those 65 and older, protection against repeat infection was only 47%.

Unvaccinated people who had COVID-19 are more than twice as likely as fully vaccinated people to get COVID-19 again, Nordlund said.

Studies are still being done, she said, to better understand whether repeat infections are milder than initial ones.

"The immune responses developed during the first infection should offer some protection against severe symptoms the second time around.".

Though it should be relatively easy to count how many people get infected after vaccination – data the CDC stopped collecting this spring – it's much more challenging to learn how many people are getting repeat COVID-19 infections.

Countries that have tried to rely on natural infections to slow the spread of the virus, such as Brazil and Iran, "have not prevented recurrent waves of infection," Glatter said