- A single injection of the Pfizer or Moderna vaccine offers high protection for people who have taken COVID-19.
- This is likely to happen because their bodies are responding to a viral threat that they have already seen.
- Giving people who took COVID-19 a second dose is “a kind of missed injection,” said an expert.
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In the race to get coronavirus vaccines to arms as quickly as possible, scientists think they have found a way to speed up the process: give people who have already taken COVID-19 just one dose.
Most Americans eligible for the vaccine are receiving the vaccine from Pfizer or Moderna, both of which require two doses administered several weeks apart. But a growing chorus of researchers now agrees that a single dose of either vaccine will generate a sufficient immune response among people who have already had the coronavirus. Giving the second dose, research suggests, is essentially a waste of a good dose.
“For those who have been infected and recovered, who are tens of millions of people, they will need only one injection, which will make the vaccine go even further,” Dr James Hildreth, president of Meharry Medical College, told Insider . .
Hildreth served on the advisory committee of the Food and Drug Administration, which recommended all three vaccines authorized against coronavirus in the United States. The third, from Johnson & Johnson, is a single-dose vaccine, so people who took COVID-19 would receive a single dose of it, no matter what.
Given that more than 29 million Americans had COVID-19, that could be up to 15 million photos from Pfizer or Moderna that could go to other people.
New research supports the strategy of an attempt
Once a person has had COVID-19, their immune system must recognize the virus if it invades again. Therefore, when a vaccine stimulates the body to start producing antibodies again, it is logical that the immune system builds a stronger and faster defense.
In a letter in the New England Journal of Medicine on Wednesday, 32 researchers from the Icahn School of Medicine on Mount Sinai wrote that a single-dose strategy for people who have already had the virus “requires investigation”.
The team found in a small study that people who had already taken COVID-19 developed 10 to 45 times more antibodies after the first dose of the Pfizer or Moderna vaccine than an ordinary uninfected person. The research is still awaiting peer review.
“The first dose ends up serving as a backup,” said Dr. Jeremy Faust, an emergency physician at Brigham and Women’s Hospital, to Insider. “If you have been infected, it is very likely that a dose will be very good for a long time.”
However, there are a few caveats: people may need to confirm that they still have antibodies if they have been sick for some time, as antibody levels decrease over time. An antibody test would also be necessary for those who suspect they have COVID-19, but have never tested positive. If the antibody test is positive, the second injection is probably redundant.
“What is the point?” Akiko Iwasaki, an immunobiologist at Yale University, told Insider. “It’s kind of a missed shot.”
‘This is where politics falls behind in science’
A paramedic holds a blood sample for a COVID-19 testing program in June 2020.
Simon Dawson – Pool / Getty Images
France started recommending a single dose of vaccine for people who took COVID-19 in February.
By this time, Mount Sinai research was over and another preliminary study had also found high levels of antibodies among health professionals who had taken COVID-19 before receiving their first injection.
Dr. Mohammad Sajadi, a co-author of that study, told Insider that patients with COVID-19 typically develop antibodies about two to three weeks after the initial infection. But health workers showed high levels of antibodies a week after the first injection.
“What this shows is that individuals who have had a previous COVID infection have what we call a memory response or a memory response,” said Sajadi. “For most infections, the second time you see that microorganism, you should get a quicker response.”
Then, in late February, a study in the United Kingdom found antibody levels roughly equal between people who received the first dose of Pfizer vaccine and never received COVID-19 and those who received COVID-19 but have not yet been vaccinated. After people who took COVID-19 received their first injection, their antibody levels were 140 times higher than their maximum levels before the vaccine.
However, most countries, including the USA, still do not recommend a single dose regimen for people who have had COVID-19.
“This is where politics falls behind science,” said Iwasaki.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told NBC News in February that the idea is worth considering.
“The data looks really impressive – if you’ve been infected and you get a single dose, the momentum you get with that single dose is really huge,” said Fauci. “This is something you might want to consider, but we really want to look at the data carefully first.”
Concerns about long-term immunity
ICU nurse Megan Tschacher shows her vaccination card at UC Health Poudre Valley Hospital in Fort Collins, Colorado, December 14, 2020.
Helen H. Richardson / MediaNews Group / The Denver Post / Getty Images
Since scientists have not had much time to follow up with vaccine recipients, there is still no consensus on how long the vaccine-induced immunity lasts. This uncertainty is one of the reasons why experts are hesitant to advocate anything other than the standard two-dose regimens of Pfizer and Moderna vaccines.
Delaying or skipping the second dose puts a lot of pressure on the first dose to provide solid, long-term immune protection, Princeton University researchers wrote on Tuesday. They expressed concern that changing the dosage regimen could lead to a “wide range” of results among vaccinated people.
But Iwasaki said people who took COVID-19 could probably wait months before they get their second injection – if they need one.
“There is simply no need to do this anytime soon,” she said.
Scientists are also optimistic that, while antibody levels are known to decrease over time, T cells will provide long-term protection for those who have had COVID-19. Like antibodies, T cells have impressive memory powers that can help the immune system recognize and attack the coronavirus again.
A recent study found that people who had already taken COVID-19 developed a stronger T-cell response to an injection of the Pfizer vaccine than people who were never infected.