Monday 9 May 2022 11:35 PM Fourth Covid jab boosts immunity 'over and above' third dose, official study ... trends now

A fourth dose of Pfizer or Moderna's Covid jabs provide an 'substantial' boost to immunity against the virus, UK Government-funded research shows.

The study of around 160 Britons aged 50-80 found the quadruple-vaxxed had up to seven times more T cells and two times more antibodies 'over and above' triple-jabbed people.

There were also no clear signs vaccines are getting weaker with each dose, allaying fears that 'over-vaccinating' could cause the jabs to lose their potency.

The finding paves the way for millions more Britons to get a fourth dose later this year. 

While countries like Israel and Germany have been rolling out fourth doses to their entire population since March, currently only over-75s, care home residents and severely ill patients are being invited in the UK.

British health chiefs have confirmed an autumn Covid vaccine scheme will go ahead, although they have not decided which groups will be eligible.

The study did, however, reveal people who had high levels of antibodies and T cells before they were given a fourth dose only got a small boost to immunity.

These people may have recently been infected recently or have had their third dose more recently, meaning their immunity had not had as long to wane.

Professor Saul Faust, chief investigator of the Cov-Boost study, said this suggests there is a 'ceiling effect' on 'how high you can go' with immunity which needs to be further studied.

The researchers said still have doubts about whether a fourth dose should be rolled out to younger groups, as they are at lower risk from the virus.

As part of the latest study, the team led by researchers at the University of Southampton, gave 166 triple-jabbed people between 51 and 78 a fourth dose of Pfizer or Moderna.

All participants had previously received two doses of Pfizer or AstraZeneca, followed by a third dose of Pfizer given around seven months ahead of the fourth dose.

Patients had a blood test two weeks after their fourth dose to check antibody and T cell levels.

Their results were compared to a blood test they took four weeks after their third dose. 

The findings, published in the scientific journal Lancet Infectious Diseases, show fourth jabs boost immunity to levels 'similar to, and possibly better than, peak responses after the third dose'. 

Antibody levels after a fourth dose of Pfizer were 60 per cent higher than four weeks after the third dose, which the scientists said was a 'significant increase'.

Among those who were given a fourth dose of Moderna, antibody levels were 2.19-times higher.

The team said T cell levels were also boosted 7.32-fold among Pfizer recipients and 6.22-fold in the Moderna group.

But the scientists urged against comparing the vaccine brands. They say the results could be influenced by what time of vaccine the participants were originally given two courses of.