Though it may not seem like it, SARS-CoV-2 is still a relatively new virus, with research continuing on all aspects of it, including the extent to which contracting it provides immunity against reinfection.

That’s the issue at the heart of the debate about whether people who have had COVID-19 should get vaccinated.

A prior infection is one of the reasons some people have given for not getting vaccinated. Their body now has antibodies that will fend off another encounter with the virus, they say, so there’s no need to get the shot.

But that’s contrary to the advice medical professionals have been giving for months, and they now have a study that backs them up.

The Centers for Disease Control and Prevention’s Aug. 6 Morbidity and Mortality Weekly Report references a study conducted in Kentucky in May and June. It showed people who had been infected but weren’t vaccinated were 2.34 times more likely to get infected again as people who were vaccinated.

“To reduce their risk of infection, all eligible persons should be offered vaccination, even if they have been previously infected with SARS-CoV-2,” it states.

Natural immunity — from being infected — appears to last 90 days or more, the authors write, “but the scientific understanding of natural infection-derived immunity is still emerging.”

In particular, it’s not known how immunity against the variant people were infected with will protect them against new ones.

In another study, they write, people who had been infected with the original virus had a weaker immune response, or none at all, to the Beta variant before they were vaccinated but a heightened response after they were vaccinated.

The authors acknowledge some limitations to their work, including that it involved only about 250 patients and 500 control subjects in one state over two months. Still, they conclude, “full vaccination provides additional protection against reinfection.”

That advice comports with what National Institutes of Health Director Francis Collins wrote recently on his agency’s website, prior to the release of the Kentucky study.

“The new evidence shows that protective antibodies generated in response to an mRNA vaccine will target a broader range of SARS-CoV-2 variants …,” he wrote. “More importantly, the data provide further documentation that those who’ve had and recovered from a COVID-19 infection still stand to benefit from getting vaccinated.”

Johns Hopkins Bloomberg School of Public Health virologist Sabra Klein agrees with Collins on the advisability of people who have had COVID-19 getting vaccinated.

After one dose, she said in an interview on the school’s website, “they have immunity levels comparable to those of uninfected people who have received their second dose.”

Getting vaccinated, she said, creates antigens that “target just the spike protein — the part of the virus that is essential for invading cells. …(I)t’s like you’re making our immune system put blinders on and only be able to see that one piece of the virus.”

People who are vaccine-hesitant due to concerns about potential side effects may be overlooking the risks in gaining immunity naturally, she said.

“Vaccines are tested for their safety in ways that we could never do with a natural viral infection,” she said. “By not getting vaccinated, you’re rolling the dice. You may become severely ill. You may have to be hospitalized. You may die.”

You may also be one of the 30% of sufferers who endure “long COVID” — symptoms lasting two months or more.

“I know a teenage girl who got COVID before the vaccines were available,” Klein said. “A year later, she is trying to maintain a somewhat normal teenage life with profound fatigue. She has never recovered fully from having COVID.”


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