Booster jabs may offer good protection against illness from the Omicron variant, scientists behind a major study of the effects of third doses have suggested.
Health secretary Sajid Javid hailed the results, saying it showed boosters ‘massively drive up’ protection against the virus.
The government-funded Covboost trial, led by the University of Southampton, showed that seven different vaccines increased immunity against Covid to some extent.
Pfizer and Moderna, which are being used as boosters in the UK, gave the best overall response.
Researchers also said the findings showed promising signs that third jabs would provide protection against illness and death from the new variant.
“This data clearly shows why it’s so important to get your booster,” Mr Javid said.
“With the possible threat of the Omicron variant, it is more important than ever to get vaccinated.”
How were the booster jabs trialled?
Boosters were given to nearly 3,000 adults about three months after they received second doses of Oxford-AstraZeneca or Pfizer BioNTech.
Researchers gave participants third doses of AstraZeneca, Pfizer, Moderna, Novavax, Janssen, Curevac and Valneva – the latter two of which are no longer being produced.
What do the results show?
All seven jabs increased immunity after two doses of AstraZeneca. Six were effective following two doses of Pfizer, but some worked better than others.
They were all found to be safe, with some recipients generally only experiencing mild side effects including headaches and pain around the injection sites.
Researchers also found the jabs had a strong response to variants including Alpha and Delta, raising hopes that this will be replicated with the Omicron variant.
Moderna and Pfizer gave the best response, particularly after two doses of AstraZeneca. In those who received two doses of the latter vaccine, there was a thirtyfold increase in antibody levels after a third dose of Moderna, and a 25-fold increase after a third Pfizer jab.
T-cell numbers remained largely the same with all the vaccines.
Professor Saul Faust, trial lead and director of the NIHR Clinical Research Facility, said: “It’s really encouraging that a wide range of vaccines, using different technologies, show benefits as a third dose to either AstraZeneca or Pfizer BioNTech.
“That gives confidence and flexibility in developing booster programmes here in the UK and globally.”
He added that he hoped the Omicron variant would be “handled by current vaccines”.
How do booster jabs increase immunity against variants?
Booster doses produce long-lasting T-cells, which can destroy infected cells and are thought to protect against severe disease.
T-cells can recognise more of the virus’ spike protein than antibodies, meaning they are likely to work better against new variants.
Part of the reason Omicron has caused concern is because of it has 32 mutations on the spike protein, which helps the virus enter cells.
“We don’t understand how T-cell data correlates with real world immunity or immunological memory,” said Prof Faust. “So we think that they’re less susceptible to mutations in the spike protein and that’s what we’ve seen in the study.
“The T-cell data, even though we don’t properly understand its relationship to long-term immunity, is showing us that it does seem to be broader against all the variant strains.”
What has the reaction been from the government?
The findings come as a huge vote of confidence in the government’s booster rollout scheme. The results are understood to have prompted the UK to order another 114m doses of Pfizer and Moderna vaccines which will be used over the next two years.
Early data from the study is also thought to have been key to the decision by the Joint Committee on Vaccination and Immunisations (JCVI) to cut the gap between second and third doses to three months.
As he received his booster jab at St Thomas’ hospital in London on Thursday, prime minister Boris Johnson said: “Whatever Omicron may or may not be able to do it certainly will not negate the overall value of the boosters – so everybody should get your booster as soon as you’re called forward.”
