The letter says two in five high risk Londoners have not come forward to get the vaccine despite evidence it will save lives.
It explains that London can only re-open if case numbers remain low and is signed by Sir David Sloman, regional director of the NHS in London, Dr Vin Diwakar, medical director of the NHS in London, Mr Khan, Cllr Georgia Gould, chair of London Councils, and Professor Kevin Fenton, the London Regional Director of Public Health England.
“The capital has been profoundly affected by Covid-19,” the letter states.
“We have seen more than 700,000 confirmed cases, and we have tragically lost more than 18,000 family members, friends, neighbours and colleagues.
“The virus has exacerbated health inequalities with our Black, Asian and minority ethnic communities disproportionately affected.
“Almost 12 months on from the first national lockdown, we remember those who are no longer with us, and pay tribute to those who have sacrificed so much in the battle against this virus.”
The letter explains that there are currently more than 200 jab centres in the capital, including large sites like Crystal Palace and the Science Museum, as well as pop-up clinics in churches and mosques.
“Hope is on the horizon, and this March looks very different to last year,” the letter said.
“Soon, we could be meeting friends and families in gardens. By mid-April outdoor dining and gyms could re-open. And, by the summer, London life could return to near normal as we manage life with the coronavirus.
“This all rests on cases remaining in low numbers and on uptake of Covid-19 vaccination, which has now reached more than 22 million people in England.”
The Oxford jab had been temporarily suspended in a number of European countries over fears it caused blood clots.
But after the European Medicines Agency confirmed the vaccine was “safe and effective” on Thursday European countries have resumed their rollouts.