Rare blood clots from AstraZeneca vaccine mostly affect younger people
The rare blood clotting disorder linked to the Oxford/AstraZeneca vaccine particularly affects younger adults, the UK medicines regulator said on Thursday as it released the first breakdown by age of the jab’s adverse side-effects.
The Medicines and Healthcare products Regulatory Agency released the figures as government scientific advisers continued to debate whether everyone under 40 should be offered an alternative to the AstraZeneca jab. At present that means either the BioNTech/Pfizer or the Moderna vaccines.
The number of cases in the UK of the rare combination of blood clots with low platelet counts had reached 209, including 41 deaths, up to April 21, the MHRA said. The total reported a week earlier was 168 cases and 32 deaths.
The age breakdown shows 23 cases in people aged 18 to 29, 27 in those in their thirties, 30 in people in their forties, 59 in people in their fifties and 58 in those aged 60 and above. The age was not known in the remaining cases.
This contrasts sharply with vaccination rates. Across the UK some 7m people in their 50s have received a first dose of a Covid-19 vaccine while about 5.5m people aged under 45 have received a first dose.
“The data suggest there is a higher incidence reported in the younger adult age groups and the MHRA advises that this evolving evidence should be taken into account when considering the use of the vaccine,” it said.
The body advising the government on the use of the AstraZeneca vaccine, the Joint Committee on Vaccination and Immunisation, is deliberating over whether its guidance should be changed, so that those under the age of 40 are offered an alternative to the AstraZeneca vaccine.
“People on the committee are struggling not just about the vaccine but about our consciences,” said Robert Dingwall, professor of sociology at Nottingham Trent university, and a JCVI member.
On one side is concern around deaths possibly linked to the vaccine, on the other is the potential of deaths from slowing the vaccination rollout. “Unless you’re on the inside you don’t realise how agonising it is,” he said.
On Wednesday Sir Munir Pirmohamed, chair of the Commission on Human Medicines, which has been advising the UK government on the safety of vaccines, told the Commons Science and Technology Committee that one person in 100,000 who received the AstraZeneca vaccine reported suffering a rare blood-clotting reaction.
He added that the only risk factor for blood clotting identified to date was age, with young people showing a “higher risk” of the rare side effect, which is lethal in about a fifth of cases.
The MHRA said the estimated number of first doses of AstraZeneca vaccine administered in the UK by April 21 was 22m, giving an overall case incidence of 9.3 per million doses.
“No effective medicine or vaccine is without risk,” said Dr June Raine, MHRA chief executive. “These specific kinds of blood clots with low platelets reported following the AstraZeneca vaccine remain extremely rare and unlikely to occur.
“The benefits of the vaccine continue to outweigh the risks for most people,” she added. “It is still vitally important that people come forward for their vaccination when invited to do so.”
Other countries have placed more stringent age limitations on the AstraZeneca vaccine — typically restricting it to people aged over 55 or 65. A few, including Denmark and Norway, have decided not to use it at all.
Scientists are still investigating why vaccines such as AstraZeneca’s, which use another (harmless) virus, an adenovirus, as a carrier, can cause the rare blood clotting disorders, while the mRNA vaccines from Pfizer and Moderna, which inject coronavirus genes directly inside microscopic fatty droplets, do not.