France's top health advisory body in charge of Covid-19 vaccines recommended on Friday that recipients of a first dose of the AstraZeneca shot who are under 55 should receive a second dose with a so-called messenger RNA vaccine.
Reuters reported on Thursday that the Haute Autorite de la Sante (HAS) had opted for the dose-mixing recommendation, which has not yet been evaluated in trials.
The French decision came after European drug regulators said on Wednesday there was a possible link between AstraZeneca’s Covid-19 shot and a very small number of cases of rare blood clots.
The European Medicines Agency still concluded that the overall benefits of this "highly effective vaccine in protecting recipients from severe Covid-19 disease, hospitalisation and death outweigh the risks of this very rare event".
Some countries had already suspended use of the AstraZeneca vaccine as a precaution, but most have resumed using the shot, although some have done so with age restrictions.
“This is a logical choice and one of security,” Dominique Le Guludec, the head of the authority, told reporters.
“Our approach is absolutely not to engage in a gigantic experimentation on the French population ...We actually want to be cautious and not expose people to thromboembolic accidents, even though they are very rare,” she said.
Two mRNA vaccines, one from Pfizer and BioNTech and one from Moderna, have been approved for use in France.
Those vaccines prompt the human body to make a protein that mimics part of the virus, triggering an immune response, while AstraZeneca’s shot uses a harmless, weakened version of a chimpanzee common-cold virus to deliver instructions to generate an immune response and prevent infection.
Germany was the first European country to recommend that people under 60 who have had a first AstraZeneca shot should receive a different vaccine as a second dose.
The World Health Organisation on Friday said there was no data to recommend that countries “mix and match” Covid-19 vaccines.
But Thomas Mertens, head of Germany’s Stiko vaccine commission, defended the decision, saying mixing two different vaccines may prove more effective than giving two doses of the same shot.
“Firstly, I am sure that there is no safety risk for the vaccinated. Secondly, I am personally convinced that the immunity will be just as good in the end, maybe even better,” he told Reuters Television.
Mr Mertens said Stiko expected data from a study in England on mixing vaccines in mid-May.
The HAS also called for real-world studies to assess the immune response triggered by the mixed vaccination scheme.
It said its decision was based on an immunisation strategy known as heterologous prime-boost, in which separate doses of different effective vaccines are used to confer protection.
The HAS said that while there is little data yet available on using different vaccines in a prime-boost strategy for Covid-19, animal studies and evidence from other disease areas is encouraging.
Meanwhile Australia has finalised a deal to buy an extra 20 million doses of the Pfizer vaccine as it rapidly pivots away from its earlier plan to rely mainly on the AstraZeneca jab.
Prime minister Scott Morrison announced the deal just hours after saying Australia would stop using the AstraZeneca vaccine for people aged under 50.
He said the deal means Australia will get a total of 40 million doses of the Pfizer vaccine by the end of the year, enough to inoculate 20 million people in the nation of 26 million.
The pivot represents a significant shift in Australia’s overall approach and is likely to delay plans to have every person in the country inoculated by October.
A major part of Australia’s strategy had been the ability to make its own vaccines at home and not rely on shipments from abroad.
It had planned to manufacture some 50 million doses of the AstraZeneca vaccine, enough for 25 million people. Australia had made no plans to make any other vaccines at home.
The first Irish case of a blood clot in a person after vaccination with the AstraZeneca vaccine was reported this week in a 40-year-old Dublin woman.
The woman is being treated at the Mater hospital for cerebral venous sinus thrombosis (CVST), the blood clot in the brain that the EMA concluded was possibly linked to the jab.
The National Immunisation Advisory Committee met on Thursday to consider the EMA's finding. It is consulting with EU colleagues and is considering whether any further advice on the use of the vaccine should be issued to the Department of Health if warranted. – Agencies