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People who had COVID-19 developed at least 10 times more antibodies after their first vaccination dose than the average uninfected person who received two doses, new research shows.
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Another preliminary study similarly found that health professionals who had COVID-19 responded to their first shot as most people responded to their second.
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The researchers both suggested that post-COVID patients may only need one injection to protect them sufficiently against the disease again.
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People often report more side effects after their second coronavirus injection than their first.
But researchers at the Icahn School of Medicine at Mount Sinai found a slightly different response in patients who already had COVID-19.
Not only did these patients have stronger side effects – including fatigue, headache, chills, fever, and muscle / joint pain – after their first injection, but they also had more antibodies compared to those who had never been ill before.
In a Monday awaiting peer review, the researchers found that people who already had COVID-19 developed at least 10 times more antibodies after their first dose than the average uninfected person who received two doses.
This could mean that previously infected persons only need one injection to protect them sufficiently against getting sick again. A single shot can also help them avoid more uncomfortable side effects after a second dose.
Indeed, the researchers wrote, “by changing the policy of giving these individuals just one dose of vaccine,” they could “save unnecessary pain and release many urgently needed vaccine doses.”
The findings are supported by another preliminary study, also out Monday, which found that health professionals who had previously received COVID-19 showed higher antibody levels after their first injection compared to vaccinated individuals who had never been infected.
“It was a really big difference. It was something that we could easily see,” said Dr. Mohammad Sajadi, associate professor in the Institute of Human Virology at the University of Maryland School of Medicine, to Insider.
Typically, Sajadi said, COVID-19 patients develop antibodies about two to three weeks after their initial infection. But it didn’t take long for post-COVID patients to develop antibodies in response to a vaccine: The individuals showed high antibody levels one week after their first injection, peaking between 10 and 14 days after vaccination.
But both studies examined only a small group of vaccinated individuals – a few hundred in all. For this reason, many scientists are wary of prescribing anything other than the two-dose regimen tested in clinical trials.
“I’m a big believer in the right dosage and schedule, because that’s how the studies were conducted,” Maria Elena Bottazzi, an immunologist at Baylor College of Medicine, told The New York Times.
Post-COVID patients have a ‘memory response’
Both the Pfizer and Moderna clinical studies suggest the vaccines are safe for individuals with a history of coronavirus infections. There are some exceptions, however.
The Centers for Disease Control and Prevention recommends that people with an active infection wait for their symptoms to clear – and the standard 10-day isolation period has passed – before getting vaccinated. This also applies to people who have already received their first dose.
“The recommendations for receiving a dose of the vaccine are to not get it if you are downright sick at the time,” Dr. Sandra Sulsky, an epidemiologist and director at Ramboll, a global health sciences consultancy, previously told Insider.
But scientists still aren’t sure when vaccines are needed for previously infected individuals. Emerging research suggests that antibodies to the coronavirus can last from a few months to several years – and even then, antibody levels don’t always correlate with immunity.
For example, all participants in the Sajadi study tested positive for antibodies against the corona virus in July and August. By the time they got their shot, he said, some of them had “very, very low levels” of antibodies – but they still seemed to be building a strong response to the vaccine.
“What that shows is that individuals who have previously had a COVID infection are having a so-called recall or memory response,” Sajadi said. “With most infections, you should get a faster response the second time you see that microorganism.”
However, he cautioned that the findings only apply to people with “everyday COVID infection” – patients who developed antibodies and have since recovered from their disease.
An intermediate solution for limited doses
Sajadi said giving just one dose to post-COVID patients is a short-term strategy to address critical vaccine shortages.
With only 32 million Americans vaccinated so far, many states continue to report that they don’t have enough doses to meet demand. In recent weeks, some local health departments have even been forced to cancel vaccine appointments or shut down scheduling websites.
The CDC has now said vaccination sites can delay administering a second dose for up to six weeks – instead of the recommended three to four weeks – in “exceptional circumstances” where it is not feasible to give the second dose on time.
“In times of vaccine shortage, where every vaccine dose counts, we think the data shows that if you had a previous COVID infection, you may only need one dose for the booster,” said Sajadi. In fact, that “could be the ideal scenario” for post-COVID patients when vaccines are widely available, he added.
So far, however, researchers have only examined how post-COVID patients respond to the Moderna and Pfizer vaccines – both of which use the same mRNA technology to elicit an immune response.
Sajadi said it is difficult to know if post-COVID patients will develop a similar antibody response to Johnson & Johnson’s single-dose viral vector vaccine, which plans to file for emergency use this week.
“There is no reason to believe it would work any differently,” he said. “But you just never know until you test it.”
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Originally published