The fourth booster jab gives protection that is "over and above" what people who have had three jabs receive, a study suggests. Research is ongoing to find out how long protection lasts, and what levels of protection people have following the Covid vaccine.
The CovBoost trial keeps track of the side-effects following a fourth jab. Blood samples were taken from 166 people for scientists to examine antibodies at various time points - including 28 days after the third jab, before the fourth jab was given - on average, 200 days later, and then a fortnight after the fourth jab.
The levels of antibodies - necessary for protection - decreased between the jabs, according to the University of Southampton, but after the fourth was given, they rose higher than after the third jab. There were large boosts compared with levels seen on the day they had the fourth jab, with people having 12 to 16 times higher levels of antibodies a fortnight after their jab compared to the day they had it.
According to the study, heightened protection was also seen at a cellular level.
The study has been published in The Lancet Infectious Diseases journal. Data was examined from 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. People who had three doses of Pfizer, followed by a fourth Pfizer shot or a half-dose Moderna jab were also looked at.
There were no severe side-effects, although some people reported pain or fatigue. However a small number of people could reach a "ceiling" in terms of how protected they could be from the fourth jab.
Authors said that some people already 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.”
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’re able to live with Covid thanks to the protection provided by our phenomenal vaccine programme and a booster dose will top up your immunity to continue to keep you and your loved ones safe.”
Now, NHS Scotland is inviting certain groups for another round of Covid vaccinations amid the pandemic's third year.
People who are at high risk of the virus are being prioritised according to guidance from the Joint Committee on Vaccination and Immunisation (JCVI).
A spring dose is recommended for adults aged 75 and over (or who will turn 75 by June 30), care home residents, and people who are 12 and over who have a weakened immune system.
Eligible people will be invited by NHS Scotland to arrange their appointments.
For most this will have been a fourth vaccine dose, but for some with a weakened immune system it will have been their fifth.
The new study supports the booster campaign and will also be used by experts who will decide on the future of the vaccination programme, including deciding if those who have weaker immune systems will have more jabs.
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