Thursday, December 1, 2022

1 dose of vaccine may be sufficient

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By Dennis Thompson

HealthDay reporter

THURSDAY, February 11, 2021 (HealthDay News) – Could an injection of a coronavirus vaccine be sufficient if you suffered from a case of COVID-19 earlier in the pandemic?

Yes, new research claims.

A pair of new and small studies found that previously infected COVID patients who received their first dose of the vaccine showed the type of robust immune response that people generally tend to have after their second “booster” dose.

“People who have had COVID before, they make antibodies very quickly at much higher levels than those who had no experience with the virus,” said Dr. Viviana Simon, senior researcher on one of the studies and professor of microbiology and infectious diseases at the Icahn School of Medicine at Mount Sinai in New York.

“This led us to the conclusion that a second injection of the vaccine should not be necessary in people who have already been infected,” Simon said. “This would save vaccine doses and also limit the discomfort people experience when getting vaccinated.”

However, these results are likely questionable given the practicalities of the pandemic, other experts said.

The new papers, recently published on the medRxiv preprint server, must be peer reviewed and verified by follow-up research before a one-shot strategy can be implemented in previously infected people. will take precious time.

Future studies to determine whether a single dose of vaccine would be sufficient in any group of people “would take several months to achieve a significant response,” said Dr. Anthony Fauci, director of the US National Allergy Institute and infectious diseases.

“At that point, the amount of vaccine that would be available would almost make this issue a bit moot,” Fauci said in a briefing Monday from the White House COVID-19 response team. The current vaccine shortages are expected to disappear as Pfizer and Moderna ramp up production and other vaccine candidates receive approval from the U.S. Food and Drug Administration.

Measure the antibody response

Researchers from Mount Sinai have been following healthcare workers who have fallen ill with COVID, to see how long a natural antibody response to the new coronavirus will last and to find out if any patients are suffering from reinfection, Simon said.


When the COVID-19 vaccines were launched in December, the researchers extended their study to see how previously infected people would respond to the vaccine.

They found that the antibody response in 41 people with pre-existing immunity was equal to or better than 68 other people who never had COVID, according to the results.

This strong response occurred even in people who had either had no symptoms of their COVID infection or had lower antibody levels before receiving the first dose, Simon said.

“It makes sense if we think of the natural infection as the main one, like the first dose, then the vaccine is like the booster, or the second shot, for someone who hasn’t seen the natural infection. “Simon said.

Another study from the University of Maryland recently came to a similar conclusion: 33 previously infected people responded more strongly to their first stroke than 26 others who were never infected.

“I think there is new evidence that a person who has previously had a COVID infection may be able to achieve sufficient immunity with just one dose of a two-dose vaccine regimen,” said Dr. Amesh Adalja, principal investigator at the Johns Hopkins Center for Health Security in Baltimore. “Prior immunity by natural infection can be enhanced by vaccination to give longer lasting and more robust immunity.”

But Adalja noted that these small studies need to be verified by larger trials, as does Dr Andrew Badley, head of the Mayo Clinic’s COVID task force.

“The concept of preserving the vaccine supply by giving those who have recovered from SARS-CoV2 infection a single dose of vaccine rather than the usual two-dose regimen is a very reasonable idea that may in fact be effective, ”said Badley, a disease specialist. “Today, however, we do not have sufficient data to recommend this approach, but I would personally be in favor of testing the approach under the rubric of a controlled clinical trial.”

Memory B cells vital for immunity

Dr Thad Stappenbeck, president of inflammation and immunity at the Lerner Research Institute at the Cleveland Clinic, is hesitant to take the one-shot strategy because higher antibody levels don’t always protect people from disease serious.


“For me, that’s really the critical data here, right? It’s hospitalizations and deaths. That’s what we’re trying to avoid,” Stappenbeck said.

Clinical trials have shown that two doses are incredibly effective at creating antibodies capable of fighting not only the new coronavirus, but also variants that have emerged in recent weeks, Stappenbeck noted.

The immune system’s memory B cells are most important in this response, which shows the body has learned lessons from the vaccine, Stappenbeck said. Further study would be needed to show that a single vaccine in previously infected people would provide a sufficient boost to their immune memory.

“While the antibody level is important, these B memory cells are really critical,” Stappenbeck said. “Having a finely tuned immune response is the key to long-term immunity.”

More information

US Centers for Disease Control and Prevention has more on Vaccines against covid-19.

SOURCES: Viviana Simon, MD, PhD, professor, microbiology and infectious diseases, Icahn School of Medicine in Mount Sinai, New York City; Anthony Fauci, MD, director, US National Institute of Allergy and Infectious Diseases; Andrew Badley, MD, infectious disease specialist, Mayo Clinic, Rochester, Minn .; Thad Stappenbeck, MD, PhD, President, Inflammation and Immunity, Lerner Research Institute of Cleveland Clinic

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