The highly transmissible Delta variant of Covid-19 has rendered the prospect of herd immunity, where the majority of a country’s population becomes immune to a virus, difficult, the head of the UK’s Oxford Vaccine Group has warned.

Professor Andrew Pollard, who led the team behind the Oxford University’s Covid-19 vaccine, told the All-Party Parliamentary Group (APPG) on Coronavirus on Tuesday that the fear of another even more transmissible variant remains a possibility and therefore there is nothing that can completely stop the deadly virus from spreading.