Fully vaccinated and had Covid-19? No rush for a boost, say experts

Several studies suggest that people who have had Covid-19 and have been fully vaccinated have strong protection, including against variants, and probably do not need the boost, although the research is preliminary and the data are incomplete, according to scientists specializing in vaccines and immunology.

More is known about people who have had Covid-19 and then were vaccinated, scientists said, than those who were vaccinated and had breakthrough infections.

Studies suggest that exposure to Covid-19 does serve as a dose of the vaccine, the scientists said. Like a dose of vaccine, the real-world infection prompts the immune system to generate the antibodies, B cells, and T cells that could fight the virus in the future.

Those infected and vaccinated “just won the game,” said Dr Paul Offit, a member of the Food and Drug Administration’s vaccine advisory committee, which supports recalls for the elderly but not a widespread campaign this time around. “I wouldn’t ask them to get a booster dose. I think they just got it ”from exposure to the coronavirus.

Last week, researchers affiliated with the ZOE Covid Study app, which allows people in the UK to self-report symptoms and test results, said that a real-world infection followed by two doses of the Pfizer-BioNTech vaccine provided 94% protection for up to six months after vaccination, compared to 80% protection against vaccination alone or 65% protection against infection alone.

The researchers, who released the results by press release, relied on more than 650,000 Covid-19 test results reported by users of the app. The results have not been peer reviewed or published in a scientific journal.

The strong protection provided by the combination of a real-world infection and a vaccination doesn’t mean people might not eventually need a booster, the scientists said.

Meanwhile, some people with weakened immune systems or with underlying health issues might want to receive a booster soon, the scientists said.

Another factor that infected and vaccinated people should weigh before receiving a booster is whether the extra dose might increase their potential risk of myocarditis, an inflammation of the heart that is rare but more common in younger men after their second dose of. a messenger RNA vaccine. said Peter Hotez, dean of the National School of Tropical Medicine at Baylor University.

Several studies show that vaccines remain effective in protecting against serious illness and hospitalization, but may lose strength by protecting against infections or milder symptomatic illnesses.

The Biden administration requested booster shots to boost the molecular defenses of Covid-19, after some studies indicated that protection worsened over time and the initial series of vaccines were less effective in protecting against the Delta variant than the original strain.

In the United States, more than 186 million people are fully vaccinated, according to the CDC. The agency stopped tracking groundbreaking cases that don’t lead to hospitalization or death, but a Wall Street Journal analysis in August found that 0.1% of people fully vaccinated at the time had developed cases. .

The combination of immunity against actual infection and the protection generated by vaccination is known as hybrid immunity.

So far, data indicates that hybrid immunity offers stronger protection than just being vaccinated or infected, immunologists and epidemiologists have said.

The results suggest that people with hybrid immunity have sufficient protection without the need for a booster, experts said.

People who have been vaccinated and infected “are probably the last group that really needs the booster because they really have had three exposures,” said Dr Akiko Iwasaki, immunologist at Yale University.

Infection in the real world can be particularly additive because it exposes the body to more than the peak protein targeted by vaccines, she said.

A study published last month by CDC researchers found that unvaccinated people who have previously been infected with Covid-19 are more than twice as likely to be re-infected as fully vaccinated people who have previously had Covid-infections. 19.

Researchers at Rockefeller University in New York City said people infected with Covid-19 and later vaccinated with a messenger RNA vaccine saw an immune response 20 to 40 times greater than those who were not vaccinated, in a study published in the journal Nature in June.

Researchers at Oregon Health and Science University said the levels of neutralizing antibodies in people with hybrid immunity to the Alpha variant were 5.2 times higher than levels in people who had not been vaccinated, in a study published on the medRxiv preprint server in April. The team tested other variants and saw similar effects.

The researchers found that hybrid immunity against infection and vaccination generally confers more immunity than immunity induced by the vaccine alone, including against the variants. The study has not yet been peer reviewed or published in a scientific journal.

Only people who received their second six-month dose, received the Pfizer vaccine, and fall into multiple high-risk categories due to their age, underlying health conditions, or occupation are currently eligible for boosters. . Decisions are pending on Moderna Inc.

and Johnson & Johnson boosters.

Write to Felicia Schwartz at [email protected]