Fourth Covid vaccine boosts immunity ‘over and above’ third dose, official study finds

According to research funded by the British government, a fourth dose of Pfizer or Moderna Covid injections provides a “significant” boost to immunity against the virus.

The study of nearly 160 Britons aged 50 to 80 found that vaccinated quads had seven times more T cells and twice as many antibodies as people with triple needle stings.

Also, there were no clear signs of weakening of the vaccines with each dose, dispelling fears that “over-vaccination” might cause the lancing device to lose power.

The discovery paves the way for millions of Brits to receive a fourth dose by the end of the year.

While countries like Israel and Germany have distributed the fourth dose to their entire population since March, only people over 75, nursing home residents and critically ill patients are currently invited to the UK.

While UK health chiefs have yet to decide which groups will be eligible, they have confirmed that the Covid vaccination program will continue in the fall.

However, the study revealed that people who had high levels of antibodies and T cells before taking a fourth dose had only a small increase in their immunity.

These people may have been recently infected or have recently received the third dose; this means that their immunity should not be reduced for that long.

Professor Saul Faust, principal investigator of the Cov-Boost study, said this suggests that there is a “ceiling effect” on “how high you can go” with immunity that needs further investigation.

The researchers said they were still unsure whether the fourth dose should be distributed to younger groups, as their risk of contracting the virus is lower.

As part of the most recent study, the team led by researchers at the University of Southampton gave a fourth dose of Pfizer or Moderna to 166 people, with triple doses between 51 and 78.

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

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

Their results were compared with a blood test taken four weeks after the third dose.

Results, published in the scientific journal Lancets Infectious Diseases of the Lancets, show that fourth injections boost immunity to levels “comparable to, and perhaps better than, the peak response after the third dose.”

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

Antibody levels were 2.19 times higher among those who received the fourth dose of Moderna.

T-cell levels also increased 7.32-fold in the Pfizer recipients and 6.22-fold in the Moderna group, the team said.

But the scientists insisted on not comparing vaccine brands. They say that because participants were initially given two courses, results could be affected.

The graphs show that a fourth Covid vaccine made antibodies (top row) and T lymphocytes (bottom row) “comparable and perhaps better than the highest response after the third dose.” Each graph shows the levels of antibodies or T cells at four locations: the day of the third injection, 28 days after the third injection, the day of the fourth injection, and 14 days after the fourth injection. The graphs on the left show the levels among those receiving the fourth dose of Pfizer, and the graphs on the right show the immunity among those using the Moderna booster.

Antibodies work to prevent an infection from spreading by attacking the virus, preventing it from attaching to and infecting cells.

But if the virus breaks this defense, T lymphocytes can identify and kill infected cells to prevent them from spreading further.

These white blood cells are believed to provide longer-lasting protection against the virus than antibodies that subside within a few months. It is also more difficult to measure and quantify.

Although vaccines’ immunity against infections declines over time, they still provide a high degree of protection against serious diseases.

Professor Faust, a specialist in pediatric immunology and infectious diseases at the University of Southampton, said people of all ages got a boost in the study, but the benefits are greater for older people, whose protections wear off more quickly.

However, the researchers noted that some study participants maintained high levels of antibodies and T cells even before they received a fourth dose.

The team said that if found in other studies, this finding could be related to long-term vaccine protection or a new infection.

The researchers suggested that this group had only a small increase from a fourth hit in their immunity to the virus, suggesting a “peak” in the amount of protection a person can have against Covid.

This finding is important to policymakers because it shows that some may benefit less from the fourth blow, he added.

Meanwhile, the results showed that arm pain and fatigue were the most reported side effects of the vaccine.

Professor Saul Faust said the vaccines gave “an excellent antibody boost” seen after the third shot.

But he said it’s not as simple as saying “we have a vaccine, let’s distribute it”.

He noted that it is unclear which future variants of Covid might settle in the UK, future applications may require modified vaccines, and it may be worth waiting in a future wave and introducing another support program rather than now.

Any timelines for the decision and administration of the vaccine will be taken by the UK Health Safety Agency and the Department of Health.

But Professor Faust said the long-term data “looks really good” and that people retain protection against serious illness and death after just two or three doses.

Health Minister Sajid Javid said: “This is another piece of evidence that highlights the importance of people coming forward to be called back when they become available.

“We can live with Covid thanks to the protection afforded by our outstanding vaccination program, and a booster dose will restore your immunity to continue keeping you and your loved ones safe.”

Professor Andrew Ustianowski, clinical leader of the National Institute for Health and Care Research, which funded the study, said: is managed.

“We knew at the beginning of the year that it was important to give a fourth dose to the most vulnerable. These new research findings support this decision and give the public confidence that the fourth dose is safe and more effective than the third dose in boosting immunity against COVID-19.

“Through the unending efforts and contributions of study participants and staff in the UK, we can learn more about the use of vaccines, and vaccines continue to play a vital role, just as they did during the pandemic.”