Young people in the UK will be offered an alternative to the AstraZeneca Covid-19 vaccine due to concerns over rare blood clots.
Britain’s medicines regulator said on Wednesday those under 30 should be offered the vaccines developed by Moderna or Pfizer-BioNTech where they are available.
A review by the Medicines and Healthcare Products Regulatory Agency found 79 people suffered rare blood clots after vaccination, 19 of whom died.
Of those who died, three were under 30.
The regulator said this was not proof the vaccine caused the blood clots, but the link was getting firmer.
Authorities said the benefits of receiving AstraZeneca’s vaccine still far outweighed the risks for most people.
With more than 20 million people receiving the AstraZeneca vaccine in the UK, there was a four in one million chance of developing a blood clot.
MHRA chief Dr June Raine said the clots were “extremely rare” and the benefits of the jab were clear.
But, she said, a risk/benefit analysis of the AstraZeneca shot was more “favourable for older people but it is more finely balanced for younger people”, who were less likely to be admitted to hospital with Covid-19.
“The evidence is firming up and our review has concluded that while it’s a strong possibility, more work is needed to establish beyond all doubt that the vaccine has caused these side effects,” she said.
“The public’s safety is at the forefront of our minds.”
Minutes before the UK advice changed, Europe's medicines regulator listed rare blood clots as a possible side effect of AstraZeneca's vaccine.
But the body continued to stress that the vaccine was safe and effective.
“The benefits of the Astra Zeneca vaccine in preventing Covid-19 overall outweigh the risks of side effects,” European Medicines Agency chief Emer Cooke said.
“Covid-19 is a very serious disease with high hospitalisation and death rate. Every day the disease is causing thousands of deaths across the EU.”
Wei Shen Lim, the Covid-19 chairman of Britain’s Joint Committee on Vaccines and Immunisation, said based on the available data it was preferable for adults aged under 30 with no underlying conditions to be offered an alternative to the AstraZeneca vaccine where available.
“We are not advising a stop to any vaccination for any individual in any age group. We are advising a preference for one vaccine over another vaccine for a particular age group, really out of the utmost caution, rather than because we have any serious safety concerns,” he said.
England’s Deputy Chief Medical Officer Jonathan Van-Tam said the new guidance was a “course correction” after a successful start to Britain’s inoculation campaign.
“We must keep this in context with the enormous success we’ve had so far,” he said.
He said the timing of the UK’s immunisation campaign would remain unchanged unless there was a shortfall of deliveries of the Pfizer-BioNTech and Moderna shots.
“I’m assured that actually because of our supply situation in relation to alternative vaccines, the effect on the timing of our programme should be zero or negligible,” Prof Van-Tam said.
“That, of course, is contingent upon getting the supplies we expect to get of the alternative vaccines.”
People who have had their first dose of the AstraZeneca vaccine should still get their second dose. Only those who suffered one of these rare blood clots after the first dose should not be immunised, the MHRA said.
People with blood disorders that leave them at risk of clotting should discuss the benefits and risks of vaccination with their doctor before going for a shot.
Nearly two thirds of the cases of rare clots were seen in women, while the people who died were aged between 18 and 79.
But it was not possible to identify whether people’s age or sex made them more at risk of the rare blood clots.
On Tuesday, a trial of the AstraZeneca’s vaccine among children was paused to await the findings of the UK review.
The UK began delivering the vaccine developed by Moderna for the first time on Wednesday, bolstering the country's immunisation programme. Britain has ordered 17 million doses of Moderna's two-shot vaccine, enough for 8.5 million people.
One hundred million doses of AstraZeneca vaccine are on order, while 40 million doses of Pfizer-BioNTech’s vaccine are in the pipeline.
The success of the vaccine programme is crucial to Prime Minister Boris Johnson’s ambition to reopen the economy fully on June 21.
Mr Johnson said on Wednesday the overall benefits of vaccines were demonstrated by the drop in hospital admissions and deaths.
“You can really start to see some of the benefits of that – it’s pretty clear that the decline in the number of deaths, the decline in the number of hospitalisations, is being fuelled, is being assisted, the steepness of that decline is being helped by the rollout of the vaccines so it’s very important for everybody to continue to get your second jab when you’re asked to come forward for your turn,” he said.
Concerns are growing that a setback with the AstraZeneca shot could mean the UK misses its target to vaccinate all adults by the end of July, although the government insists it remains on track.
UK ministers have repeatedly said the benefits of the vaccine in preventing coronavirus far outweigh any risks.
“There is no proof as yet that there is any causal links on the very, very rare occasions that there have been talks about blood clots,” Business Minister Paul Scully told Sky News on Wednesday.
“The AstraZeneca vaccine is safe – it has saved thousands of lives.”
But some scientists urged caution while investigations were carried out.
Maggie Wearmouth, a member of the JCVI, suggested that “perhaps slowing things down” might be wise.
"We don't want to cover anything up that we feel that the public should be knowing," she told The Telegraph. "We're not here to blindly follow targets or due dates."
Prof Adam Finn, who advises the government on vaccines, said it was possible that Moderna or other vaccines could be reserved for younger groups in case AstraZeneca’s use was restricted.
“We are seeing another vaccine coming in and further vaccines are approaching licensure, and I know that the UK has made contracts for quite a wide range of different vaccines, so as time goes forward we’ll have much more flexibility as to who can be offered what,” he said.
Vaccination centres and pharmacies are facing a significant reduction in the supply of doses during April, meaning that older people waiting for second doses will be prioritised over younger people receiving their first shot.
A total of 40,744 first doses were given on Monday, the lowest since the government began publishing daily figures.
But Mr Johnson’s official spokesman said the UK remained on track to offer a first dose to all over-50s by April 15, and to all adults by the end of July.
“There will be a slight reduction in April, but the key thing to remember is that that doesn’t mean that we’re not on track to meet our pledges,” he said.
Three in five adults in the UK have been vaccinated so far, with the most recent data showing more than 31.6 million people have received a first dose, and 5.5 million have received a second dose.
This week’s developments are the latest blow for AstraZeneca’s vaccine. Its use is already limited to older people in several large European countries, including France and Germany, amid fears over a potential link between the shot and blood clots.
Germany and France initially approved the vaccine only for young adults because of the lack of data on its efficacy in people older the age of 65.
The shot’s reputation was further undermined by an ongoing row between the EU and AstraZeneca over supplies, leading the bloc to restrict the export of doses.
Prof Finn said any disruption to the immunisation programme could delay the lifting of restrictions.
He said scientists were investigating side effects potentially linked to AstraZeneca’s vaccine.
“What stands out about them is that we see thrombosis in the cerebral veins all the time, but we don’t necessarily see them in association with a low platelet count,” he told the BBC.
“The fact that there’s this unusual constellation of features – of thrombosis, low platelet counts and one or two other things that we measure in the blood as well – make us think that there’s something special going on.”
Calum Semple, another scientific advisor, said he was “not worried one little bit” about the blood clot reports.
“Taking an aspirin is probably more dangerous. Some people will get a stomach ulcer. That’s the thing, nothing is risk-free,” he told LBC radio.
Former health secretary Jeremy Hunt said the public would respect the regulator’s advice because the body was highly trusted.
“People will listen to their advice when it happens today and tomorrow and I think they’ll just have to be British – to keep calm and carry on – and follow that advice,” he said.
“People understand that the vaccine programme is saving lives but they also understand that advice changes.”