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Some scientists have called on governments to administer single doses of Covid-19 after preliminary research suggested they appear to offer some degree of protection, although manufacturers recommend two doses. But other scientists warn that a single inoculation is not enough to confer lasting immunity.
Food and Drug Administration (FDA) analyzes of Moderna and Pfizer vaccines found that a single dose of either appears to provide some protection against the coronavirus.
The effectiveness of a dose of Moderna vaccine was around 80 to 90%, researchers said, in stage 3 trials, before its approval by the U.S. regulator in January.
Scientists have found that the Pfizer-BioNTech jab is 70% effective with one dose, compared to 95% with two.
After approving the Oxford-AstraZeneca vaccine, UK regulators said it was around 70% effective within 12 weeks of the first dose.
With vaccine supply limited across the world, these findings raise a key question for governments and healthcare professionals: does it make more sense to vaccinate fewer people with both doses for maximum protection, or better distribute vaccinations, by inoculating more widely but less completely?
Some have suggested that governments should strive to give as many people as possible a single dose, instead of using half of the vaccines currently available on second doses.
Moderna “didn’t hesitate to show that a single dose was so effective, and they do the math right,” Chris Gill, an infectious disease specialist at Boston University, told WBUR, the NPR affiliate in Boston. .
Therefore, governments should distribute as many single doses as possible as soon as possible, said Gill: “We could save a lot of lives. We can now give people two doses, but in the meantime a group of people who could have been vaccinated will die. Isn’t this an example where, once 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 claiming the UK government should use “all available doses in January as the first doses, that is not to withhold half for the second doses “in the hope that” even the first dose will provide substantial immunity “.
But others warn that more research needs to be done and that by then it makes more sense to administer the vaccines in two separate doses, as planned.
“If the second dose of vaccine was unnecessary and we knew [it] did not extend the term of protection, the principle would be to protect as many people and save as many lives as possible, ”Barry Bloom, epidemiologist at Harvard University, told WBUR.
Pfizer scientists warned in a statement Thursday that they were not too convinced that a dose would provide sufficient long-term protection.
There is “no data” to show that protection after the first dose is maintained after 21 days, they wrote.
Administering a second dose is important because it increases the chances of returning to normal life by giving people lasting immunity, suggested Jean-Daniel Lelièvre, head of the immunity and infectious diseases department at Henri-Mondor hospital in Créteil near Paris. . “The purpose of a second dose is to prolong immunity, and as it stands, there is no evidence that a single dose would confer the same level of protection,” he told the French daily. The world.
The French government will continue to distribute two doses as recommended, Health Minister Olivier Véran told France Info on Saturday. France will follow manufacturers’ guidelines to administer the Pfizer-BioNTech vaccine, which the French national regulator approved on December 24. The inoculations started three days later.
‘No data’ to support mix-and-match jabs in UK
Across the Channel, the UK government changed its vaccine guidelines on December 30 to allow the second dose of Pfizer-BioNTech and Oxford-AstraZeneca injections to be given for up to 12 weeks after the first, instead three weeks as originally planned.
The UK government also said in guidelines released on December 31 that in rare cases people could receive a mix and match of two Covid-19 vaccines – despite a lack of evidence on the extent of immunity offered. by mixing doses.
The two vaccines are meant to be given as two shots, several weeks apart, but they were not designed to be mixed.
Yet UK health officials have said that if “the same vaccine is not available, or if the first product received is unknown, it is reasonable to offer a dose of the product available locally to complete the schedule.”
Mary Ramsay, head of vaccinations at Public Health England, said this would only happen on very rare occasions and the government does not recommend mixing vaccines.
“Every effort should be made to give them the same vaccine, but where that is not possible, it is better to give a second dose of another vaccine than not at all,” she told Reuters .
Some have warned that the new UK guidelines could have been born out of desperation.
“There’s no data on this idea at all,” John Moore, a vaccine expert at Cornell University, told the New York Times.
Health officials in Britain “seem to have given up on science altogether now and are just trying to figure their way out of the mess,” Moore said.
(FRANCE 24 with REUTERS)
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