Scientists studying the effects of so-called booster vaccines said the body’s T cell immune response, after a third jab, is such that it may provide protection from hospital admission and death.
The CovBoost study – published in The Lancet – also appears to legitimise the UK’s decision to primarily offer Pfizer-BioNTech or Moderna as a third shot, with mRNA jabs leading to the most significant rise in immunity levels.
Health secretary Sajid Javid announced on Wednesday that the government had bought 114 million more doses of the two vaccines, following advice from the Joint Committee on Vaccination and Immunisation (JCVI) to put them at the top of the list.
However, Professor Saul Faust, trial lead and director of the NIHR Clinical Research Facility at University Hospital Southampton NHS Foundation Trust, said researchers had found that AstraZeneca, Novavax and Janssen were all safe and effective booster doses for people already double-jabbed with Pfizer or AstraZeneca – as most people in the UK are.
No vaccine posed any safety concern, according to the study, with fatigue, headache and a sore arm the most commonly reported issues, which Prof Faust described as “really encouraging”.
“That gives confidence and flexibility in developing booster programmes here in the UK and globally, with other factors like supply chain and logistics also in play,” he said, adding the jabs worked well against existing variants, such as delta, but that omicron was not tested in the study.
It is thought that T cell immunity, which was studied in the trial alongside antibodies, could play a “significant role” in fending off the new variant – first discovered in southern Africa. The cells play a key role and work alongside antibodies in the immune system to target viruses.
Prof Faust said of the development: “Even though we don’t properly understand its relation to long-term immunity, the T cell data is showing us that it does seem to be broader against all the variant strains, which gives us hope that a variant strain of the virus might be able to be handled, certainly for hospitalisation and death if not prevention of infection, by the current vaccines.”
Asked specifically about omicron, Prof Faust added: “Our hope as scientists is that protection against hospitalisation and death will remain intact.”
When looking at antibody levels in the trial, people who had received two doses of AstraZeneca initially had booster responses that were between 1.8 times higher to 32.3 times higher, depending on the booster vaccine used.
After two doses of Pfizer, the range was 1.3 times higher to 11.5 times higher, with the study’s authors warning these ratios should be interpreted “with caution” as they do not relate to real-world protection against disease.
Samples from the CovBoost trial, which involved 2,878 people aged 30 or over receiving a booster 10 to 12 weeks after their initial two-dose vaccination, have now been passed to the UK Health Security Agency (UKHSA) to consider how well omicron can be neutralised by vaccines.
Jonathan Ball, professor of molecular virology at the University of Nottingham, hailed the “fantastic study” as being a “great [way] to finally see the data that was no doubt pivotal in deciding the UK’s vaccine booster approach”.
“The fact that the mRNA vaccine boosts gave a marked increase in both antibodies and T cells is great news, especially now, when our attention has been grabbed by the emergence of the omicron variant,” Prof Ball told the PA news agency.
Researchers noted additional data from the trial will be published next year, including immunity statistics and whether a longer period between second and third vaccine doses improves the response.
Speaking after receiving his own booster jab on Thursday, Boris Johnson once again instructed the British public to refrain from cancelling Christmas plans in the face of omicron, saying there’s “no need”.
“The most important thing you can do in all circumstances is get your booster when you’re called,” the prime minister told Sky News. “We’ve done 18.6 million booster jabs in this country, so we’re building ever higher the wall of protection.”
He added: “Whatever omicron may or may not be able to do, it certainly will not negate the overall value of the boosters.”
Additional reporting by PA
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