Fourth Covid jab can give higher immunity than initial booster, study finds

All participants had initially had either two doses of the Pfizer/BioNTech jab or two doses of the Oxford/AstraZeneca vaccine. Photograph: Kirsty O’Connor/PA

A fourth dose of a Covid vaccine can ramp up the body’s immune defences beyond the peak achieved after a third dose, research suggests.

A second booster – often a fourth dose of a Covid vaccine – is currently offered in the UK to those aged 75 or over, people living in care homes for older people, and those over the age of 12 who are immunosuppressed.