LONDON (BLOOMBERG) - The UK will offer under-40s an alternative to the AstraZeneca Covid-19 vaccine because of concerns about very rare blood clots that so far appear to be more common in younger people.
The decision, announced Friday (May 7), follows a recommendation by UK scientific advisory panel the Joint Committee on Vaccination and Immunisation.
The precautionary measure comes as authorities prepare to open up the inoculation programme to people under 40, after those over 40 were invited to book their first shots in the last week.
The AstraZeneca vaccine has been the workhorse of the UK programme to date.
The new strategy means that where supplies permit, people aged under 40 will be offered vaccines by Pfizer-BioNtech or Moderna - the only two other shots with current approval for use in the UK.
The change won't impact plans to offer all adults a vaccine by the end of July and is based on the current rate of infection, the prospect of a third wave, and the pace of vaccine rollout.
The decision comes a month after the UK decided to offer under-30s alternatives to the AstraZeneca shot because of what officials described as "extremely rare" incidences of blood clotting. At the time, 79 cases had been recorded, including 19 deaths out of more than 20 million doses administered.
The risk of the rare clots based on the current data is 10.5 people in every million after a first dose, a number that rises to 17.4 per million in those ages 30 to 39.
"Our position remains that the benefits of the Astra vaccine "outweigh the risks for the vast majority of people," Dr June Raine, chief executive of the U.L Medicines and Healthcare products Regulatory Agency, said in a statement Friday.
"The balance of benefits and risks is very favourable for older people but is more finely balanced for younger people and we advise that this evolving evidence should be taken into account when considering the use of the vaccine, as JCVI has done."
Astra has said it is working to understand the individual cases, epidemiology and possible mechanisms that could explain the events.
More recent data from April 28 shows that after some 28.5 million doses of the AstraZeneca shot had been delivered, there had been 242 cases of the blood clots, including 49 deaths.
The overall risk of death from the clots is 2.1 in every million, a number that increases to 4.5 per million in the 30 to 39 age group.
The UK's vaccine programme is estimated to have prevented more than 10,000 deaths in England alone by the end of March, according to the Department of Health and Social Care.
The European Union's drug regulator issued an analysis of the Astra clot data two weeks ago that showed if virus spread was low, the risk of side effects outweighed potential prevention of death or ICU admission in people under the age of 50.
Still, the vaccine protected against hospitalisation and the overall benefits still outweighed the risks, the European Medicines Agency said.