Vaccination with two doses of the Pfizer jab stays highly effective against severe Covid — including the Delta variant — for at least six months, an analysis of US patients said.

While previous data from clinical trials has shown jabs protect against hospitalisation, the study published in the Lancet measures one vaccine's effectiveness over time in a real-world setting.

After an average period of three to four months, fully vaccinated people were found to be 73 per cent protected against infection and 90pc protected against hospitalisation, AFP reported.

But while protection against infection from Delta fell by 40pc over five months, protection against hospitalisation involving cases from all variants remained very high for the duration of the study.