COVID-19 immunity makes severe breakthrough infections extremely rare, study confirms

ROCHESTER, Minn. — Whether you opted to get the COVID-19 vaccine or contracted the virus already, a new study finds having immunity to COVID makes it highly unlikely you’ll end up in the hospital with a breakthrough infection.

Researchers from the Mayo Clinic say less than one in 1,000 people who were either vaccinated or previously infected with coronavirus needed hospitalization for a breakthrough case of COVID. The team adds their review of more than 106,000 patients provides even more evidence that vaccination is the best way to protect against severe COVID-19 cases, hospitalization, and death.

“In the general primary care patient population, those who have been vaccinated have very low risk of subsequent hospitalization for breakthrough COVID-19,” says lead author Benjamin Pollock, Ph.D., a researcher in the Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery, in a media release. “Our study shows that while it can and does happen, that these occurrences are extremely uncommon.”

Immunity keeps people out of danger

Among 106,349 vaccinated patients testing positive for COVID-19 at the Mayo Clinic, just 69 needed hospitalization due to a breakthrough infection. Overall, that’s just six in every 10,000 vaccinated patients.

The study also found just three in 10,000 patients who previous had COVID-19 needed hospitalization for a breakthrough case. Just one in 10,000 patients who were vaccinated and had a prior COVID infection had a severe breakthrough.

“We found these results to be in line with previous studies, although the interpretation shouldn’t necessarily be that natural immunity provides the same protection as vaccination,” says Dr. Pollock. “Rather, this study found that among our primary care population, both natural immunity and vaccine immunity appeared to lead to very low rates of breakthrough hospitalizations.”

The team notes they did not compare the rates of breakthrough cases between vaccinated individuals and people with natural immunity through prior infection if they only had mild symptoms.

“We know that vaccination remains the safest route to protection from COVID-19 infection and severe disease,” says co-author Aaron Tande, M.D., a Mayo Clinic infectious diseases physician. “I explain to my patients that a COVID-19 vaccine provides additional protection, even if they have been previously infected. For those who have not been infected, vaccination remains the safest and most reliable route of protection.”

Which immunity is better?

Despite some studies finding that natural immunity can provide more protection against breakthrough COVID cases becoming severe, study authors say there is still enough evidence that the COVID-19 vaccine is the easier and safer way to stay out of the hospital.

“Because it’s impossible to tell in advance how severe a first infection may be, or who among vulnerable populations the virus may spread to, waiting for natural immunity is a gamble and not a safe alternative,” Dr. Tande says.

The findings appear in the journal Clinical Infectious Diseases.

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