People under the age of 30 will be offered alternatives to the AstraZeneca vaccine after the UK medicines regulator said there was a possible link between the jab and “extremely rare” blood clots.
The Medicines and Healthcare products Regulatory Agency (MHRA) said the benefits of the vaccine still outweigh the risks overall, but while it has not concluded that the vaccine causes rare brain clots, it says the link is getting firmer.
The MHRA said the balance of risk for the AstraZeneca vaccine is very favourable for older people but “more finely balanced” for younger groups, who do not tend to suffer serious Covid illness.
As a result, people aged 18 to 29 will be offered the Pfizer, Moderna or other jabs that come on stream as the vaccination programme rolls out across the UK.
Separately, a review by the European Medicines Agency (EMA) concluded on Wednesday that “unusual blood clots with low blood platelets should be listed as very rare side effects” of the Oxford/AstraZeneca vaccine.
Emer Cooke, executive director of EMA, said its review “confirmed that the benefits of the AstraZeneca vaccine in preventing Covid-19 overall outweigh the risk of side effects”, adding: “Vaccination is extremely important in helping us in the fight against Covid-19.”
Dr Sabine Straus, safety committee chairwoman at the EMA, said: “This vaccine has proven to be highly effective, it prevents severe disease and hospitalisation and it is saving lives.
“Vaccination is extremely important in helping us in the fight against Covid-19 and we need to use the vaccines we have to protect us from the devastating effects.”
Up to March 31, the MHRA in the UK has received 79 reports of blood clots accompanied by low blood platelet count, all in people who had their first dose of the vaccine, out of around 20 million doses given.
Of these 79, a total of 19 people have died, although it has not been established what the cause was in every case.
The 79 cases occurred in 51 women and 28 men, aged from 18 to 79.
Of the 19 who died, three were under the age of 30, the MHRA said.
Some 14 cases of the 19 were cerebral venous sinus thrombosis (CVST), a specific type of clot that prevents blood from draining from the brain.
The other five cases were other kinds of thrombosis in major veins.
The figures suggest the risk of rare blood clot is the equivalent to four people out of every million who receive the vaccine.
Meanwhile, in Europe, the EMA has carried out an in-depth review of 62 cases of CVST and 24 cases of splanchnic vein thrombosis in which 18 people died.
The MHRA’s chief executive, Dr June Raine, said there is a “reasonably plausible” link between the AstraZeneca jab and rare blood clots.
“The evidence has accrued not only in numbers and kinds of cases but the pattern of those cases,” she said.
“So we feel it’s a much more solid basis in our regulatory world to put in the side effect into our product information and that tells us it is a reasonably plausible link.”
However, she said the clots were “extremely rare”, adding: “Based on the current evidence, the benefits of the Covid-19 vaccine AstraZeneca against Covid-19 and its associated risks – hospitalisation and death – continues to outweigh the risks for the vast majority of people.
“Our review has reinforced that the risk of this rare suspected side effect remains extremely small.”
Andrew Pollard, professor of paediatric infection and immunity, and lead investigator of the Oxford University trial of the vaccine, said safety had been a “priority” throughout its development last year.
He added: “We are reassured to see that safety monitoring continues under the close scrutiny of regulators and public health authorities as the vaccine is rolled out around the world.
“The identification of rare cases of blood clots, which might be associated with the vaccine, shows that the safety system works, and has also allowed MHRA and EMA to conclude that the benefits of vaccination continue to outweigh the risks, while putting in measures to help mitigate any possible risk.”
Professor Wei Shen, chairman of the Joint Committee on Vaccination and Immunisation, said the recommendation to prefer other vaccines to AstraZeneca for the under-30s was “out of the utmost caution” rather than because of “any serious safety concerns”.
Meanwhile, Professor Sir Munir Pirmohamed, chairman of the Commission on Human Medicines, said any risks from the jab had to be set against the fact around 30% of people with Covid suffer low blood platelet counts, while Covid also “causes clotting”.
Some 7.8% of people with Covid suffer blood clots on the lungs, while 11.2% will suffer deep vein thrombosis (DVT), he added.
He said there appears to be a “slightly higher risk in the younger age group” of clots after the AstraZeneca vaccine, but the reason is “not clear” with further work required.
On possible explanations for the clots, he said: “The early evidence suggests that this constellation of symptoms is caused by an immune response against platelets which allows the platelets to then lead to clotting in different parts of the body.
“But what we don’t have clearly is the link between the vaccine and how the immune response becomes activated against the platelets.”
England’s deputy chief medical officer Professor Jonathan Van-Tam used a nautical analogy to describe the “course correction” in the vaccination programme.
He told the briefing it was “quite normal” for medics to alter their preferences on how to treat patients.
He said changes were made to the flu vaccine programme a few years ago and “changes in preference for vaccines are business as usual”.
He added: “This is a massive beast that we are driving along at enormous pace with enormous success, this vaccine programme.
“If you sail a massive liner across the Atlantic then it’s not really reasonable that you aren’t going to have to make at least one course correction during that voyage.”
He said it would be “pretty absurd” to withhold the AstraZeneca vaccine from the over-40s.
“The idea of withholding a vaccine where a potential harm, for example in the 40-49 group, is 0.5 harms per 100,000 people versus 51.5 intensive care admissions averted, and that’s not taking into account hospitalisations, long Covid and spreading to others, then the notion that you would clip the vaccine at that point is pretty absurd really.
“So it is very much an independent decision but I think it has been taken in an extremely rational way.”
The MHRA said that those who have had their first dose of the AstraZeneca vaccine should still get their second dose.
Only those who suffered a rare blood clot after the first dose should not get vaccinated.
Anyone 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 jab.
Ms Cooke, from the EMA, defended the decision not to follow the UK in recommending that those under the age of 30 be offered another vaccine.
She said the available data did not allow the EMA to draw any causal link with age groups, or whether male or female, adding: “There is a lot more use in younger age groups in the UK than there is in the EU at the moment and we will take this into account in our further evaluations.”
Prime Minister Boris Johnson said: “We will follow today’s updated advice, which should allow people of all ages to continue to have full confidence in vaccines, helping us save lives and cautiously return towards normality.”