Are younger people at risk of blood clots linked to AstraZeneca vaccine?

UK health regulator reportedly considering proposal to restrict use of jab in some age groups

Decisions taken by European countries to limit the Oxford-AstraZeneca vaccine to older people has contributed to growing interest in any possible risk posed to younger recipients of the jab.

The UK’s health regulator is reportedly considering a proposal to restrict the use of the vaccine in younger people over concerns about very rare blood clots.

“Two senior sources have told this programme that while the data is still unclear, there are growing arguments to justify offering younger people – below the age of 30 at the very least – a different vaccine,” Channel 4 News reported on Monday.

The UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) has said that no decision has been taken and previously stressed that the benefits of the vaccine in preventing people falling seriously ill or dying from Covid far outweighed any possible risk of blood clots.

“Our thorough and detailed review is ongoing into reports of very rare and specific types of blood clots with low platelets following the Covid-19 Vaccine AstraZeneca,” June Raine, MHRA chief executive, said. “No decision has yet been made on any regulatory action.”

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However, earlier on Monday Professor Neil Ferguson, a leading scientist who sits on the government’s New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG), said the development of blood clots in people who had been given the AstraZeneca vaccine raised questions over whether young people should be given it.

“In terms of the data at the moment, there is increasing evidence that there is a rare risk associated, particularly with the AstraZeneca vaccine but it may be associated at a lower level with other vaccines, of these unusual blood clots with low platelet counts,” the adviser, who has had the Oxford jab, told the BBC Radio 4 Today programme.

“It appears that risk is age related, it may possible be – but the data is weaker on this – related to sex.

“And so the older you are, the less the risk is and also the higher the risk is of Covid so the risk-benefit equation really points very much towards being vaccinated.

“I think it becomes slightly more complicated when you get to younger age groups where the risk-benefit equation is more complicated.”

Prof Ferguson said the MHRA and the Joint Committee on Vaccination and Immunisation (JCVI) were “considering this matter very urgently” but added: “No vaccine, no medicine is risk free – it is always about a balancing equation against risk.”

On 30 March, Canadian provinces suspended the use of the vaccine in people aged under 55 after a recommendation by the country’s National Advisory Committee on Immunisation (NACI), which cited reports of “rare cases of serious blood clots” in Europe.

A day later, Germany took the decision to suspend the routine use of the AstraZeneca vaccines for people under the age of 60.

The Netherlands has also temporarily suspended use of the AstraZeneca jab for people under 60 following the death of a woman who had recently received the vaccine.

Rollout of AstraZeneca vaccines continues to be paused or age-restricted in several other European countries, including Denmark, Finland, France and Sweden. Only around a dozen EU nations offer it to all adults, including Spain, Ireland, Italy and Portugal.

The general view has been that since older people are much more likely to become ill or die from Covid, the risk-benefit analysis leans heavily towards taking a vaccine. Whereas younger people have a lower risk of illness or death from coronavirus, making decisons over vaccine risk more nuanced.

Saad Shakir, director of the Drug Safety Research Unit in Southampton, who is conducting a review of the AstraZeneca vaccine rollout in the UK, told the Financial Times that there was a chance younger people who tend to have stronger immune systems would on rare occasions experience immune overreactions to the vaccine.

The situation is further complicated because of the piecemeal way in which various European countries have administered the vaccines.

Germany, for example, initially only offered the AstraZeneca to the under-65s, citing a lack of data on its effectiveness in older age groups, and only later reversing that decision. Experts say the fact that the jab has been administered to only certain age groups at certain times could affect the data.

The European Medicines Agency said in its preliminary review of a possible link to blood clots in people vaccinated with the AstraZeneca jab that the benefits of the vaccine in combating the threat of Covid – which itself results in clotting problems and may be fatal – continue to outweigh the risk of side effects and that the vaccine is not associated with an increase in the overall risk of blood clots in those who receive the jab.

However, the EMA said the vaccine may be associated with very rare cases of blood clots associated with low levels of blood platelets, including rare cases of clots in the vessels draining blood from the brain.

Most of the blood clot cases the EMA analysed occurred in people under 55 and the majority were women.

Overall the number of clotting events reported after vaccination, both in studies before licensing and in reports after rollout of vaccination campaigns, was lower than that expected in the general population.

“However, in younger patients there remain some concerns, related in particular to these rare cases,” the review, dated 18 March, said.

The regulator said that there were a higher number of cases of clotting among the under-55s than would be expected in the general population, while a “similar imbalance was not visible in the older population given the vaccine”.