AstraZeneca has begun the worldwide withdrawal of its Covid-19 vaccine due to a “surplus of available updated vaccines” since the pandemic.
The company said it would proceed to withdraw Vaxzevria's marketing authorisations within Europe.
Regulator, the European Medicines Agency, has confirmed the vaccine is no longer authorised for use.
“As multiple, variant Covid-19 vaccines have since been developed there is a surplus of available updated vaccines,” the company said, adding this had led to a decline in demand.
The Anglo-Swedish drugmaker's decision came after a statement to the High Court in London in February confirmed that its vaccine “can, in very rare cases, cause TTS” (Thrombosis with Thrombocytopenia Syndrome), a form of blood clot.
Cases were found in people with a low blood platelet count.
It is estimated that between two and three per 100,000 people who were vaccinated had this adverse effect.
Adam Finn, professor of paediatrics at the University of Bristol and head of the Bristol Children's Vaccine Centre, said the the withdrawal is likely not related to the rare side effect.
He told Radio 4's Today show on Wednesday: "It's turned out that this virus is very agile, and it's evolved away from the original vaccines. So they have in a sense become irrelevant and only the reformulated vaccines are likely to be being used now.
"And of course, we're in a very different place, with almost everyone at the population immune to Sars-CoV-2. So the need for this vaccine I think has evaporated now."
Nevertheless, the relationship between the vaccine and TTS has been known for some time, he said.
AstraZeneca vaccine - in pictures
He added: "It's completely clear that this vaccine and the other one [using] this platform, a viral vector from Johnson & Johnson, was associated with this thrombocytopenic thrombosis syndrome. I think that's been clear for a long time, although perhaps only recently acknowledged.
"But I don't think that's really relevant to this withdrawal. I think the withdrawal of the vaccine is simply reflects the fact that it's no longer useful and so not going to be being used anymore."
The firm's application to withdraw the vaccine was made on March 5 and came into effect on May 7, according to the UK's Daily Telegraph.
Patients who say they were left with permanent health problems and are suing the drug maker, though some cases were recently dropped after being told the presence of a small print warning means their case would probably fail.
Gareth Eve, whose BBC radio presenter wife Lisa Shaw died three weeks after receiving her first dose, is among a number of parties who have pulled out of the High Court legal action.
They were told their claim was unlikely to succeed because a leaflet, handed out at vaccination centres, warned of “extremely rare cases of blood clots with low levels of platelets” after vaccination with the AstraZeneca shot.
It is believed the warning, issued on April 7, 2021, could protect AstraZeneca from cases in which relatives died after receiving vaccines beyond that date.
A dozen families have now dropped out of the legal action as a result.
But more than 50 of relatives of people who received the vaccine before the warning was added are continuing with the lawsuit.
The vaccine, developed with scientists from the University of Oxford, was seen as pivotal given its low cost and the fact it could be stored in a normal fridge rather than super-cold storage.
London-listed AstraZeneca began moving into respiratory syncytial virus vaccines and obesity drugs through several deals last year after a slowdown in growth as Covid-19 medicine sales declined, Reuters reported.
Scientists are still learning much about the effects of Long Covid, which is thought to affect millions of people.
Great hope
The launch of the AstraZeneca vaccine was seen as a milestone in the battle against the Covid-19 pandemic.
The first clinical trial for the vaccine started in January 2020, around the same time when reports of the first cases emerged in China.
It built on previous work to create an adenovirus-based vaccine against the Middle Eastern Respiratory Syndrome (MERS) coronavirus, making it a case of ‘copying and pasting’ the genetic code for the spike protein for the virus that causes Covid into the platform's harmless chimp adenovirus to create the ChAdOx1 nCoV-19 vaccine.
By early February, the lab had tested a lab version of the vaccine in mice, which revealed strong immune responses, suggesting the vaccine would work.
Human volunteers received their first doses in April 2020.
On 23 November 2020, it was announced the vaccine was successful, with 70.4% efficacy in preventing symptomatic Covid more than 14 days after receiving two doses of the vaccine.
"We were involved in Bristol in collaboration with Oxford a number of other centres in doing research on this vaccine and I very clearly remember the day in November 2020, when the results came through. And it turned out that it worked," said Prof Finn.
"And we were able to see very early on that even just one dose of this vaccine was saving many, many lives.
"It was a very remarkable period and we really didn't know what to expect, as it came through. Of course, we've never had the experience of developing a vaccine in such a short period of time. But the truth is, it made an enormous difference. It was what as you said at the beginning was what lifted us out of the catastrophe that was unfolding at the time, combined with the other vaccine from Pfizer."
