According to research, the fourth dose of a Covid vaccine can boost the body’s immune system beyond the level reached after a third dose.
In the UK, a second booster – typically the fourth dose of a Covid vaccine – is currently available to people over 75 and to those living in care homes for older people and those with immunosuppression over 12 years of age.
Scientists have discovered a fourth injection can revive immune responses that have waned since a third shot.
Researchers involved in the UK-based Cov-Boost trial reported their findings in the Lancet Infectious Diseases in relation to immune responses in 166 participants who received a fourth Covid vaccine on average seven months after having received a third Pfizer/BioNTech shot. Pfizer/BioNTech or Oxford/AstraZeneca vaccines were first administered to all participants in two doses.
As their fourth vaccination, half of them received a full dose of the Pfizer/BioNTech Covid vaccine, while the other half received a half dose of the Moderna vaccine. The vaccines did not cause any serious adverse events.
A study of 133 participants found that 14 days after receiving the fourth vaccine, the Pfizer/BioNTech group had a 1.6-fold increase in antibodies, and the half-dose Moderna group saw a more than two-fold increase, compared with 28 days after receiving the third dose, when antibodies were at their highest.
There were increases in both the over 70s and under 70s.
Furthermore, both types of fourth vaccination resulted in substantial increases in antibodies and T cells within 14 days of the fourth vaccination.
In addition to our results for immunogenicity, the Israeli observational evidence on vaccine effectiveness indicates that a fourth-dose booster can provide an increased level of protection against symptomatic infection and severe illness, the researchers write.
Fust’s research also shows that those who had a limited decline in their immune response before the booster dose gained only a modest boost after the booster – and similar findings for others with a recent history of infection with Covid. According to him, there may be a ceiling on how high antibodies can be with T-cell response effects.
According to some experts, those yet to reach middle age might never receive another Covid jab in the current climate.
“The fact that our first-generation vaccines falter rapidly and give rather permeable protection today does not mean we should stop boosting them,” he said.
Since many of us, even with high apparent antibody levels, actually, show [very little] protection from Omicron, it is even more important to use [fourth] doses – in all age groups – to boost levels back up to protective levels.