Some scientists have called on governments to issue single doses of Covid-19, after preliminary research suggested that they appear to offer some protection, despite producers recommending two doses. But other scientists warn that one vaccination is not enough to grant lasting immunity.
The Food and Drug Administration (FDA) analyzed both the Moderna and Pfizer vaccines and found that a single dose of some degree provides protection against the coronavirus.
The efficacy of one dose of Moderna vaccine was about 80 to 90 percent, researchers found in Phase 3 trials before it was approved by the U.S. regulator in January.
Scientists have found that the Pfizer-BioNTech jab is 70 percent effective with one dose, compared to 95 percent effective with two.
After the Oxford-AstraZeneca vaccine was approved, UK regulators said it was about 70 percent effective in the twelve weeks after the first dose.
Given the limited supply of vaccines worldwide, such findings pose a key question for governments and medical professions: Does it make more sense to vaccinate fewer people with both doses for maximum protection, or is it better to spread and vaccinate more widely? but less complete?
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 in second doses.
Modern was ‘not ashamed to show that a single dose is so effective, and they do the math right’, Chris Gill, an infectious disease specialist at Boston University, told WBUR, Boston’s NPR branch , said.
As a result, governments need to deliver as many doses as possible, Gill argued: “We can save many lives. We can now give two doses to people, but in the meantime a lot of people who could get the vaccine are dying. Is not this an example of where the enemy of the good is still perfect? ‘
In the UK, where a new, more contagious coronavirus acceleration is accelerating transmission, former Prime Minister Tony Blair wrote an opinion piece in The Independent on 22 December, arguing that the British government ‘has all the available doses in January as first doses should be used is, not to withhold half for second doses “in the expectation that” even the first dose will provide considerable immunity “.
But others warn that more research needs to be done, and that until then it makes more sense to administer the vaccines in two separate doses, as designed.
‘If the second vaccine dose was superfluous, we knew [it] “If the protection period had not been extended, the principle would be to protect as many people and save as many lives as possible,” Barry Bloom, an epidemiologist at Harvard University, told WBUR.
Pfizer scientists warned in a statement on Thursday not to be overconfident that one dose would provide enough protection in the long run.
There is ‘no data’ showing that protection is maintained after the first dose after 21 days, they wrote.
The administration of a second dose is important because it increases the chances of getting life back to normal by giving people lasting immunity, said Jean-Daniel Lelièvre, head of the Department of Immunity and Infectious Diseases at the Henri-Mondor de Créteil- hospital near Paris, proposed. “The purpose of a second dose is to prolong immunity, and as it currently stands, there is no evidence that a single dose will provide the same protection,” he told French daily Le Monde.
The French government will continue to give two doses as recommended, Health Minister Olivier Véran told France Info on Saturday. France will follow the manufacturers’ guidelines when administering the Pfizer-BioNTech vaccine, which was approved by France’s national regulator on 24 December. Vaccinations started three days later.
‘No data’ to support UK mix-and-match jabs
Across the channel, the British government changed its vaccination guidelines on 30 December to allow the second dose of Pfizer-BioNTech and Oxford-AstraZeneca jabs to be administered up to 12 weeks after the first, instead of three weeks as originally planned .
The British government also said in guidelines published on 31 December that in rare cases people could get a mixture of two Covid-19 vaccines – despite a lack of evidence on the degree of immunity offered by mixed doses.
Both vaccines are intended to be administered as two shots, with a few weeks apart, but they are not designed to be mixed.
Yet UK health authorities have 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 vaccinations at Public Health England, said this would only happen in extremely rare cases, and that the government did not recommend mixing vaccines.
“We should try everything 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 British guidelines may have been born out of desperation.
“There is no information at all about this idea,” John Moore, a vaccination expert at Cornell University, told The New York Times.
Health officials in Britain ‘have apparently now left science completely and are just trying to guess their way out of a mess’, Moore said.
(FRANCE 24 with REUTERS)