A fourth dose of Pfizer or Moderna's Covid jabs provide a “substantial” boost to immunity against the virus, UK Government-funded research shows.
The study of around 160 Brits aged 50-80 found the quadruple-vaccinated had up to seven times more T cells, a defensive white blood cell, and two times more antibodies 'over and above' triple-jabbed people.
However, the research also revealed that people who had high levels of antibodies and T cells before they were given a fourth dose only got a small boost to immunity.
In a new study published in The Lancet, the "safety, reactogenicity, and immunogenicity" of fourth-dose boosters against Covid was analysed, in particular Pfizer and Moderna.
In the study, which was led by researchers at the University of Southampton, 166 triple-jabbed people, aged between 51 and 78, were given a fourth dose of either the Pfizer or Moderna vaccine.
All the study participants had previously received two doses of either Pfizer or AstraZeneca, followed by a third dose of Pfizer.
Patients then had a blood test two weeks after their fourth dose to check their antibody and T cell levels, which were compared to a blood test they took four weeks after their third one.
The study found that the fourth jabs helped to boost immunity levels “similar to, and possibly better than, peak responses after the third dose.”
Antibody levels after a fourth dose of Pfizer were 60% higher than four weeks after the third dose, which the scientists said was a “significant increase.”
When it came to a fourth Moderna dose, antibody levels were 2.19-times higher.
The research team said T cell levels were also boosted 7.32-fold among Pfizer recipients and 6.22-fold in the Moderna group.
Another study, published in the New England Journal of Medicine, delved further into the protection of a fourth dose of a Pfizer vaccine to protect against the subvariant Omicron.
Using the Israeli Ministry of Health database, data was extracted on 1,252,331 people who were 60 years of age or older and eligible for the fourth dose.
“We estimated the rate of confirmed infection and severe Covid as a function of time starting at eight days after receipt of a fourth dose (four-dose groups) as compared with that among persons who had received only three doses (three-dose group) and among persons who had received a fourth dose three to seven days earlier (internal control group),” noted the study.
“The number of cases of severe Covid-19 per 100,000 person-days was 1.5 in the aggregated four-dose groups, 3.9 in the three-dose group, and 4.2 in the internal control group.”
The study found that protection against severe illness did not wane during the six weeks after receipt of the fourth dose.
It concluded: “Rates of confirmed SARS-CoV-2 infection and severe COVID-19 were lower after a fourth dose of BNT162b2 (Pfizer) vaccine than after only three doses.
“Protection against confirmed infection appeared short-lived, whereas protection against severe illness did not wane during the study period.”
The World Health Organisation (WHO) hasn’t given an official recommendation on a fourth dose, and at this point stated “there isn’t any good evidence at this point of time” that it will be beneficial, according to chief scientist Soumya Swaminathan.
“What we know from immunology is that if you give another booster, you will see a temporary increase in the neutralising antibodies.
"But what we’ve also seen is that these neutralising antibodies will wane quite rapidly,” Swaminathan told CNBC in an interview.
“This happened after the third dose. And it’s happened again after the fourth dose,” she added.
