- Some experts believe that people who have had COVID-19 should receive only one dose of two-dose coronavirus vaccines.
- This would provide protection for these people while releasing vaccine doses to others, they say.
- However, other experts warn the approach can be logistically difficult and scientifically ‘risky’.
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Experts are divided on whether people who have already had COVID-19 need a complete coronavirus vaccination course to protect them from re-infection.
Early studies show that these people produce robust immune responses after just one dose of two-dose COVID-19 vaccines, such as those made by Pfizer and BioNTech, AstraZeneca and Oxford University and Moderna.
Some experts argue that it would be safe to give up the second shot for these people, and it would free up vaccines for others. They effectively say that a previous COVID-19 infection could act like the first shot. France made this position its official policy on 12 February.
Other experts, including dr. Anthony Fauci, the leading expert on infectious diseases in the US, said it was still too early to make this call – but even he says the results of these early trials are ‘very impressive’.
According to Johns Hopkins University, more than 115 million people worldwide are infected with COVID-19. The figure includes more than 28.8 million people in the US, more than 4.2 million in the UK and more than 3.8 million in France.
“If you could save a dose for every person who had COVID-19, it would be a lot of doses,” Lawrence Young, a virologist at the University of Warwick in the UK, told Insider.
Fauci, President Joe Biden’s chief medical adviser, told NBC on February 21 that the immunity boosted a single COVID-19 vaccine shot to people who had the virus was ‘enormous’, and that the data ‘was really impressive. “
The US government therefore looked ‘very nicely’ to see if one dose was enough – but it was still too early to make a change, Fauci said.
Johnson & Johnson’s COVID-19 vaccine, which was approved in the United States in February, requires only one shot.
Evidence is increasing for the protection of single shots for those who have had COVID-19
A U.S. study of more than 100 people showed that those previously infected with COVID-19 had an antibody response to one dose of vaccine 10 times higher than people who were not infected and received two doses.
The authors of the study, from Mount Sinai, New York, also said that those who had previously had COVID-19 experienced more side effects after vaccination – such as a more painful or redder injection site – than those who were not infected. . By giving just one shot, they can reduce the side effects.
The study, published on February 1, was a preview and has not yet been reviewed by other peers in a peer review.
Another U.S. group from Maryland Medical School found that health workers who were previously infected had a 500-fold increase in antibody response from baseline at 14 days, after a single shot. “The response was greater and faster than those who did not have COVID-19,” Mohammad Sajadi, an associate professor of medicine at the Institute of Human Virology at Maryland University, told Insider. The study was published March 1 in the Journal of the American Medical Association.
Initial clinical trials did not see this phenomenon because volunteers at the time probably did not catch COVID-19, Sajadi explained.
A study in the UK among 51 health workers published in a February 25 correspondence with the medical journal Lancet reported a 140-fold increase in baseline antibody levels in people previously infected with COVID-19 after a single dose – more than those who have caught the virus before.
Another study in the UK among 72 health workers in London, published in the same journal on the same day, showed that those who had a previous COVID-19 infection produced 25 times more antibodies against COVID-19 as people who have not yet been. previously infected, and their T cell responses – another important part of the immune system – were about ten times higher, 21 days after the first dose.
The Mount Sinai researchers said that changing policy around individuals who had COVID-19 could promote one dose of vaccine, which could release many “urgently needed” doses.
Sajadi also said that it is a solution to the shortages of vaccines that will not require many resources.
“In the US, 9% of people were diagnosed with PCR or antigen tests, which would free up a 4-5% increase in vaccine supply without examining extra antibodies,” Sajadi said.
Assuming the total vaccine supply in the US by the end of June was 500 million doses, it could release thousands of millions of doses.
A health care worker up front gets a vaccine against Modern COVID-19 at the Park County Health Departments store clinic on January 5, 2021 in Livingston, Montana.
Photo by William Campbell / Getty Images
Sajadi said we did not yet know how long people would be protected after their first shot if they had COVID-19 before, but he said there was evidence that antibody reactions could take up to nine months. Immunity to other coronaviruses decreases over time.
He said isolating the second dose would not work for everyone. People with a weakened immune system, or low antibody levels after COVID-19 infection – like older people – would be in a different group. This is the case in France.
The authors of the UK study among 75 health workers, who do not advocate a change in vaccine policy, said their study suggested that people over 50 and those not previously infected with COVID-19 had a weaker immune response to ‘ have a single dose of vaccine. .
Sajadi said it was also not yet clear what advice would be given to people with ‘long COVID’, that is, people with COVID-19 symptoms that last longer than a few weeks, because the single-dose approach has not been tested here. not group.
Cannot guarantee protection
Other experts are skeptical. “We do not know what kind of immunity, duration of immunity, or strength of immunity that dual-dose vaccine provides, compared to a single dose on top of past infection,” Jonathan Ball, professor of molecular virology, told the University of Nottingham, said. , Insider said.
“While you would argue that this is a way to save a dose of vaccine, you can not guarantee that it has as much protection as someone who receives both.”
Ball said that, according to the serious side effects, no one appeared to his knowledge for those previously infected with COVID-19 and who received two vaccine shots.
“Scientifically it’s not crazy, we do not have the same amount of data as for clinical trials [that tested two doses]”Ball said.” It would be a brave decision to suddenly introduce it as a policy. ”
Ball said that where there was a serious issue, there might be new ways to meet the demand, such as prioritizing those who did not have COVID-19 for the first doses, but we still need to take care that everyone eventually gets two doses.
Professor Paul Morgan, director of the Systems Immunity Research Institute at Cardiff University, told Insider that only giving a shot to those who already had COVID-19 was “a good idea, but risky”.
Morgan said immunity differs between individuals. “Some are better prepared to defend themselves than others,” he said.
Morgan said it would be “cumbersome, time-consuming and a lot of money” to determine who would be eligible for such a scheme.
Young also said the mass vaccination effort was already a logistical challenge, and changing the approach could slow the explosion of the vaccine.
“People will not know if they had COVID-19, and we will also have to find out how much immune response they had,” he said.
It is also not yet clear whether science contains other, more contagious coronavirus variants.
“It changes the equation,” Sajadi said. “The vaccine may play a role in boosting or altering the immune response in those who have had COVID-19 before, but more information is needed.”