The UK is preparing to become the first big country to administer “mix and match” coronavirus vaccines for its booster programme, according to senior government figures. Many Britons are expected to have a third, booster dose that is different to their first two jabs, on the basis that it would provide better protection against Covid-19, said the government insiders. Ministers want to press ahead with an autumn booster campaign after separate studies from Oxford university and the team behind the Zoe Covid app found that the protection against symptomatic infection provided by the BioNTech/Pfizer and the Oxford/AstraZeneca vaccines waned four to six months after second doses. A final decision by the government on its booster plan will be made once the Joint Committee on Vaccination and Immunisation, an advisory body, has made a recommendation. The UK’s vaccination programme has been dominated by AstraZeneca, which has been found to have lower effectiveness against infection with the Delta variant of coronavirus compared with Pfizer. However, some studies have suggested that AstraZeneca’s effectiveness declines more slowly than Pfizer’s. The JCVI has been preparing its guidance for the government about the booster programme.
Members of the JCVI met on Thursday to analyse data from the University of Southampton’s Cov-Boost trial. It has looked at antibody responses among people who were initially given AstraZeneca or Pfizer jabs when they are subsequently given one of seven different vaccines as a third dose. Previous research has suggested benefits in mixing and matching vaccines. An Oxford university study, published in June, showed people who received a first jab of AstraZeneca followed by a second of Pfizer experienced a nine-fold increase in antibody levels compared with those who had two doses of AstraZeneca. Danny Altmann, professor of immunology at Imperial College London, said a combination of AstraZeneca and a vaccine using mRNA technology such as Pfizer “may give better, longer-lasting protection when used together”. Government officials said it was expected that many people would receive a booster vaccine different to the one used for their first two doses. One senior Department of Health insider said: “We’ll be giving Pfizer to those who had AstraZeneca the first time, and AstraZeneca to those who had Pfizer. It’s the best combination to get as much protection as possible.” Another senior Whitehall official confirmed that mixing doses was “how we’re going to do the autumn booster programme”.
The Department of Health said in response to a request for comment: “Our independent regulator, the MHRA, has confirmed the AstraZeneca and Pfizer vaccines are safe and effective to be used as booster jabs and third doses for people who are immunosuppressed. “We continue to prepare for an autumn booster programme . . . Any booster programme — including which vaccines might be recommended for use — will be based on the final advice of the independent Joint Committee on Vaccination and Immunisation.” Israel, the country furthest along with its booster programme, relies on Pfizer, which has been mainly used for initial vaccine doses. The US is likely to stick to giving the same vaccines, based on trial data for third doses provided by manufacturers.
But other countries have administered mix and match doses for first and second jabs. In Europe some governments approved mixing after concerns about a very rare side effect from AstraZeneca involving blood clotting led them to allow people who had been given it as a first dose to then have a different second vaccine. In Turkey and Thailand, where there were concerns about efficacy of the Sinovac Chinese vaccine, some were offered an additional dose of Pfizer. Clive Dix, former head of the UK government’s vaccines task force, said it was well known in scientific circles that “heterologous boosting” was more effective in increasing people’s immune response than giving another dose of the vaccine the individual had originally received. “The science of vaccinology has shown . . . that if you boost somebody with a different vaccine construct you tend to get a stronger response than if you give them the same one again,” he added.