UK government scientific advisers are split on whether to recommend that all under-40s should be offered an alternative to the Oxford/AstraZeneca vaccine, as cases of the rare blood-clotting condition linked to it continue to rise.
Britain abruptly changed tack last month on the AstraZeneca jab, the mainstay of its vaccination programme, after the Joint Committee on Vaccination and Immunisation (JCVI) advised that all healthy individuals under the age of 30 should be offered an alternative, if available.
The move followed growing evidence that the shot could trigger a blood disorder in extremely rare cases and an assessment of the risk it posed in various age groups compared with the benefits.
A study by the Winton Centre for Risk and Evidence Communication at Cambridge university released at the time showed that only for those adults under 30 were the risks posed by Covid-19 and the jab comparable, depending on infection rates.
The JCVI is now debating whether the same advice to offer an alternative to the AstraZeneca jab, if possible, should be extended to the healthy cohort under 40, when the mass vaccination programme begins for them next month.
Some scientists on the committee are calling for the effective restriction to be extended to those aged 30 to 39, while others argue there is still insufficient evidence to make a decision that could risk denting confidence in the vaccine.
The JCVI is expected to make a decision as early as next week, according to one of its members, but is waiting for more data, including the analysis of blood samples from some of those affected by the blood disorder.
“I would for sure support giving people who are 30 to 40 another vaccine,” said Maarten Postma, professor in pharmacoeconomics at the University of Groningen in the Netherlands, and a member of the JCVI. “There are alternative [vaccines] so we can be careful.”
The latest data from the UK’s Medicines and Healthcare products Regulatory Agency on Thursday showed 68 new cases of the blood disorder in people who had received the AstraZeneca shot were reported in the last week.
The clotting condition has led to 32 deaths in 168 affected people aged between 18 and 93 in the UK with 21.2m doses of the AstraZeneca vaccine administered so far. One case was reported in an individual following their second shot of the vaccine.
Postma added that the overall risk-benefit balance for all ages was clearly in favour of continued use of the vaccine, given that statistically 1,000 Covid-19 deaths would be prevented for every 1m people inoculated, while scientists would expect one fatal case of the blood disorder.
“But people do not think in terms of risk-benefit,” he said. “We give these vaccines to healthy people so there’s zero tolerance when it comes to severe side effects.”
Another member of the JCVI, who backs an alternative jab for the under-40s, said the risk-benefit calculation of the AstraZeneca vaccine for those in their 30s “doesn’t really square up”.
The incidence rate of the clotting condition for people in that age group who had the AstraZeneca jab appeared to be between 1 in 50,000 to 1 in 100,000, the person said. While modelling suggests roughly 1 in 30,000 to 1 in 50,000 people need to be vaccinated to prevent a single death in the same cohort from Covid-19, the JCVI member added.
Others on the committee are more sanguine. Robert Dingwall, professor of sociology at Nottingham Trent University and a member of the JCVI, said he believed there was enough uncertainty about the exact relationship between the vaccine and the clotting disorder to justify giving AstraZeneca to those between 30 and 39.
“Offering an alternative to AZ to all under-40s would be a big step in terms of confidence,” he said, adding that any effective restriction would slow the rollout of the UK’s vaccine programme and increase the risk to those who remain unvaccinated.
Analysts at Airfinity have previously estimated the change in guidance for the use of AstraZeneca in the under-30s could set the UK’s inoculation drive back by a month.
Andrew Pollard, director of the Oxford Vaccine Group, said the JCVI had to make the “best decisions on the evidence they have.” AstraZeneca declined to comment.