Drop in Pfizer's efficacy in Israel against Delta variant is NOTHING to worry ...

Britons under the age of 40 will be offered their second Covid jab after eight weeks instead of 12.

Boris Johnson claimed the new aim was for all adults to be fully inoculated by mid-September, when coronavirus rates are expected to rise and the NHS grapples with seasonal winter pressures.

Last month, the gap was shortened for older people in a bid to protect millions of the most vulnerable amid the rise of the highly-infectious Indian variant.

The Prime Minister announced the change to the dosing strategy at tonight's press conference, where he set out plans for a post-lockdown England from July 19.

Ministers are also considering whether to roll out third vaccines for all over-50s, NHS staff, carers and patients with underlying health conditions this autumn.

Oxford University researchers last week showed antibody levels could be restored to their peak with the use of a 'booster' vaccine months after the second.

But whether or not this would improve on the already near-100 per cent protection against death that two doses provide is still unknown.

No10 is now wrestling with the moral dilemma of whether to run the booster vaccine programme or send the doses to developing countries where supplies are scarce.

Vaccinating children is another contentious strategy being considered by the Government, with some of its advisers warning that Covid itself is less dangerous to youngsters than a jab.