Several countries have now deployed fourth doses of the Covid-19 vaccine, but the clinical need, efficacy, timing and dose of a fourth dose remain uncertain
Image: Getty Images)
A fourth dose of either Pfizer or Moderna’s Covid shots boosts immunity to the virus “significantly”, UK government-funded research shows.
The study of around 160 Britons aged 50 to 80 found that those who were vaccinated quadruple had up to seven times more T cells, a defensive white blood cell and twice as many antibodies than those who were vaccinated three times.
However, the research also found that people who had high levels of antibodies and T cells before the fourth dose received only a small boost in immunity.
A new study published in The Lancet analyzed the “safety, reactogenicity and immunogenicity” of fourth-dose boosters against Covid, specifically those from Pfizer and Moderna.
In the study, led by researchers from the University of Southampton, 166 triple-vaccinated people between the ages of 51 and 78 received a fourth dose of either the Pfizer or Moderna vaccine.
All study participants had previously received two doses of Pfizer or AstraZeneca, followed by a third dose of Pfizer.
The patients then underwent 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 dose.
The study found that the fourth doses helped boost immunity “similar to and possibly better than the 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 researchers said was a “significant increase.”
At a fourth dose of Moderna, antibody levels were 2.19 times higher.
The research team said T-cell levels were also increased 7.32-fold in Pfizer recipients and 6.22-fold in the Moderna group.
Another study, published in the New England Journal of Medicine, looked in more detail at protecting a fourth dose of a Pfizer vaccine against the Omicron subvariant.
Using the Israel Ministry of Health database, data was extracted from 1,252,331 people aged 60 years or older who were eligible for the fourth dose.
“We estimated the rate of confirmed infections and severe Covid as a function of time starting eight days after receiving a fourth dose (four-dose groups) compared to people who had only received three doses (three-dose groups). and in people who had received a fourth dose three to seven days previously (internal control group),” the study said.
“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 the protection against serious illnesses did not decrease in the six weeks after receiving the fourth dose.
It concluded: “The rates of confirmed SARS-CoV-2 infection and severe COVID-19 infection were lower after a fourth dose of the BNT162b2 (Pfizer) vaccine than after only three doses.
“Protection against confirmed infection appeared to be short-lived, while protection against severe disease did not diminish over the study period.”
The World Health Organization (WHO) has not made an official recommendation for a fourth dose, stating at the time “there is currently no good evidence” that it will be beneficial, according to lead scientist Soumya Swaminathan.
“What we know from immunology is that if you give another booster shot, you’re going to see a transient rise in neutralizing antibodies.
“But what we’ve also seen is that those neutralizing antibodies are going to wear off pretty quickly,” Swaminathan said in an interview with CNBC.
“It happened after the third dose. And it happened again after the fourth dose,” she added.
https://www.mirror.co.uk/lifestyle/health/coronavirus-booster-pfizer-moderna-26936718 The fourth Covid vaccine offers “a significant boost in immunity”, according to a new study.