Many people around the UK have had three separate Covid jabs in a bid to boost their immunity against the virus, and discussion is being had over whether a fourth would be necessary.
Research is continuing to assess the levels of protection people have after vaccination, and for the length of time that this protection lasts.
People aged 75 years and over, those in care homes and those aged 12 years and over with a weakened immune system have already been offered a fourth (or fifth in some cases) jab in the form of the spring booster.
The question might remain for some people about if a fourth jab is needed for them.
Will I need a 4th Covid jab?
A team of academics led by the University of Southampton have been tracking a group of people and their levels of antibodies and T cells, both measures which indicate a person’s level of protection against a virus.
The CovBoost trial also examined side effects after a fourth jab.
Some 166 people took part in the study and offered blood samples, which means that scientists could examine the concentration of antibodies in the blood.
These were examined at various time points, including 28 days after the third jab was given; again just before their fourth boost was administered – which took place, on average, just over 200 days later; and then 14 days after they had their fourth jab.
The levels of antibodies waned in the period between third jabs and fourth boosters.
But a fortnight after the booster jab antibody levels rose even higher than the levels seen after the third jab.
There were significant boosts compared with the levels seen on the day they were given their fourth booster – participants had 12 to 16 times higher levels of antibodies in the blood a fortnight after they got their fourth shot, compared with the day it was delivered.
Boosts were also seen in the cellular level, according to the study, which has been published in The Lancet Infectious Diseases journal.
Researchers examined data on people who had two doses of the AstraZeneca jab, followed by a Pfizer booster, who then received either a Pfizer jab or half dose of a Moderna jab for their fourth vaccine.
They also looked at people who had three doses of Pfizer, followed by a fourth Pfizer shot or a half-dose Moderna jab.
No severe side-effects were recorded among participants, with some reporting pain or fatigue.
Immunity better for some after 3rd jab
A different outcome was seen for some of the participants in the study which provided a “hint” that a small number of people might reach a “ceiling” in terms of the amount of protection that they could get from a fourth jab.
The authors said that some people had high levels of immune response “even before the fourth dose and had limited boosting from the fourth dose”, including people who had just been infected with the virus.
Trial lead Professor Saul Faust, director of the NIHR Southampton Clinical Research Facility, said: “These results underline the benefits of the most vulnerable people receiving current spring boosters and gives confidence for any prospective autumn booster programme in the UK, if the Joint Committee on Vaccination and Immunisation considers it needed at that time.”
When can I have my 4th Covid jab?
Currently, you can't get a fourth Covid jab unless you are over the age of 75, live in a care home or are over the age of 12 and have a weakened immune system.
A wider group of people will be offered an autumn booster, although the details of that programme haven't yet been confirmed.
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