The latest Covid-19 shots give people protection “beyond” that given to people who have had three shots, a new study suggests.
Research is continuing to assess the levels of protection people have after vaccination and how long this protection lasts.
A team of academics led by the University of Southampton has been tracking a group of people and their levels of antibodies and T cells, both measures that indicate a person’s level of protection against a virus.
The CovBoost trial also looked at side effects after a fourth injection.
Some 166 people participated in the study and offered blood samples, which means that the scientists were able to examine the concentration of antibodies in the blood.
These were examined at various times, including 28 days after the third injection was given; again just before his fourth booster was given, which was, on average, just over 200 days later; and then 14 days after they received their fourth needle stick.
Antibody levels decreased in the period between the third injections and the fourth booster doses.
But fifteen days after the booster injection, antibody levels increased even more than the levels seen after the third injection.
And there were significant increases compared to levels seen on the day they received their fourth booster: Participants had 12- to 16-fold higher blood antibody levels a fortnight after receiving their fourth shot, compared to the day they received their fourth booster. was administered.
Increases were also seen at the cellular level, according to the study, which was published in The Lancet Infectious Diseases.
The researchers examined data from people who received two doses of the AstraZeneca injection, followed by a Pfizer booster, who then received either a Pfizer injection or half the dose of a Moderna injection for their fourth vaccination.
They also looked at people who had three doses of Pfizer, followed by a fourth shot of Pfizer or a half dose of Moderna.
No serious side effects were recorded among the participants, with some reporting pain or fatigue.
But the authors said the study provided a “hint” that a small number of people might hit a “ceiling” in terms of the amount of protection they might get from a fourth injection.
The authors said that some people had high levels of immune response “even before the fourth dose and had a limited boost from the fourth dose,” including people who had just been infected with the virus.
Trial leader Professor Saul Faust, Director of the NIHR Southampton Clinical Research Facility, said: “These results underscore the benefits of the most vulnerable people receiving the current spring boosters and give confidence for any potential autumn booster schedule in the United Kingdom, if the Joint Committee on Vaccination and Immunization deems it necessary at that time”.
Health and Social Care Secretary Sajid Javid added: “This is further evidence underlining the importance of people coming forward for their booster as soon as they are eligible.
“We can live with Covid thanks to the protection provided by our phenomenal vaccine program and a booster dose will boost your immunity to continue to keep you and your loved ones safe.”
Various groups have been called out for a spring booster, including those over 75, people living in nursing homes for the elderly, or people over the age of 12 who have weakened immune systems.
For most, this will have been a fourth dose of vaccine, but for some with a weakened immune system it will have been the fifth.
The new study supports the booster campaign and will also be used by experts who will decide on the future of the vaccination program, including whether or not people with weakened immune systems should get more injections and whether or not the booster program should be implemented to include other groups.
So far, more than three million people have received their spring booster in England alone, according to NHS England.