Some scientists have called on governments to dispense a single dose of Covid-19 after preliminary research suggested they appear to provide some degree of protection, despite manufacturers recommending two doses. But other scientists warn that one shot is not enough to provide lasting immunity.
Food and Drug Administration (FDA) analyzes of both the Moderna and Pfizer vaccines showed that a single dose of both appears to provide some protection against the coronavirus.
The efficacy of a single dose of Moderna vaccine was about 80 to 90 percent, researchers found in phase 3 studies prior to US regulatory approval in January.
Scientists found that the Pfizer-BioNTech shot is 70 percent effective with one dose, compared to 95 percent effective with two.
After approving the Oxford AstraZeneca vaccine, UK regulators said it was about 70 percent effective in the 12 weeks after the first dose.
Since stocks of vaccines are limited around the world, such findings raise an important question for governments and medical professionals: does it make more sense to vaccinate fewer people with both doses for maximum protection or is it better to distribute vaccines and scale them up? to inoculate? but less complete?
Some have suggested that governments should strive to give as many people as possible a single dose, rather than using half of the vaccines currently available in second doses.
Moderna was “not shy about showing that a single dose was so effective, and they count well,” Chris Gill, an infectious disease specialist at Boston University, told WBUR, Boston’s NPR subsidiary.
That’s why governments should give as many single doses as possible as soon as possible, Gill said: “We can save many lives. We can now give two doses to humans, but in the meantime, a number of people will die who could have received the vaccine. Isn’t this an example of where, again, the perfect is the enemy of the good? “
In the UK, where a new, more contagious strain of coronavirus is accelerating transmission, former Prime Minister Tony Blair wrote an opinion piece in The Independent on December 22 stating that the UK government should ‘use all available doses in January as first doses, that is , do not withhold half for second doses ”in the expectation that“ even the first dose will provide substantial immunity ”.
But others warn that more research needs to be done, and until then it makes more sense to give the vaccines in two separate doses, as intended.
‘If the second vaccination dose was unnecessary, and we knew [it] did not extend the duration of the protection, the principle would be to protect as many people as possible and save as many lives as possible, ”Barry Bloom, an epidemiologist at Harvard University, told WBUR.
Scientists at Pfizer warned in a statement Thursday that they were not too sure that one dose would provide sufficient long-term protection.
There is “no data” showing that protection lasts after the first dose after 21 days, they wrote.
Administering a second dose is important because it increases the chances of returning life to normal by giving people lasting immunity, says Jean-Daniel Lelièvre, head of the Immunity and Infectious Diseases Department at Henri-Mondor de Créteil Hospital near Paris. “The purpose of a second dose is to maintain immunity, and as things stand, there is no evidence that a single dose would provide the same level of protection,” he told French daily Le Monde.
The French government will still dispense two doses as recommended, Health Minister Olivier Véran told France Info on Saturday. France will follow the manufacturer’s guidelines when administering the Pfizer-BioNTech vaccine, which was approved by France’s national regulator on December 24. The vaccinations started three days later.
‘No data’ to support UK mix-and-match jabs
Across the Channel, the UK government changed its vaccine guidelines on December 30 to give the second dose of both the Pfizer-BioNTech and Oxford-AstraZeneca shots up to 12 weeks after the first, instead of three weeks as originally planned.
The UK government also said in guidelines published December 31 that in rare cases, people could be given a mix and match of two Covid-19 vaccines – despite a lack of evidence on the level of immunity afforded by mixing doses .
Both vaccines are intended to be given as two injections several weeks apart, but they were not intended to be mixed.
Still, the UK health authorities said that if “the same vaccine is not available, or if the first product received is unknown, it is reasonable to offer one dose of the locally available product to complete the schedule”.
Mary Ramsay, head of immunizations at Public Health England, said this would only happen on very rare occasions and that the government does not recommend mixing vaccines.
“Every effort should be made to give them the same vaccine, but if this is not possible, it is better to give a second dose of a different vaccine than not at all,” she told Reuters.
Some warned that the new British guidelines may have been born out of desperation.
“There is no data at all on this idea,” John Moore, a vaccine expert at Cornell University, told The New York Times.
Health officials in Britain “now seem to have left science completely and are just trying to guess their way out of a mess,” Moore said.
(FRANCE 24 with REUTERS)