The coronavirus vaccine has been offered to residents at every eligible care home with older people in England, official figures are expected to confirm on Monday.
NHS England said people living at more than 10,000 care homes with older residents had been offered the jab.
A small number of homes had visits deferred for safety reasons during a local outbreak but would be visited as soon as it was safe for NHS staff to do so, a spokesman for NHS England said.
Prime Minister Boris Johnson said: “Today marks a crucial milestone in our ongoing race to vaccinate the most vulnerable against this deadly disease.
“We said we would prioritise and protect care home residents, and that is exactly what we have done.
“There will be difficult moments to come, and the number of cases and people in hospital remains dangerously high.
“But vaccines are our route out of the pandemic, and having protected 8.9 million people with a first dose so far, our rollout programme will only accelerate from here on.”
Staff are also returning to homes to deliver vaccines to any residents who were unable to have it on the previous visit for clinical reasons.
NHS England’s primary care director Dr Nikki Kanani said: “I want to thank my colleagues, and everyone involved in the vaccine rollout for their extraordinary work in recent weeks, as it is because of their tireless efforts that millions of people have already been vaccinated, including hundreds of thousands of care home residents, and as a result we are a vital step further in our fight against Covid-19.
“It has been a privilege to vaccinate some of the most vulnerable people and the wonderful people who look after them.
“Many have had little contact with the outside world throughout the pandemic and so it has been truly humbling for all, giving them hope and importantly protection against the disease.”
Older adult care home residents and staff were made high priority groups by the Joint Committee of Vaccinations and Immunisations (JCVI).
NHS chief executive Sir Simon Stevens said: “This important milestone in protecting the vulnerable is the result of amazing partnership working between our GPs, community nurses and care homes.
“And with over two million more people vaccinated in communities across England this past week, the NHS’s Covid vaccination campaign is off to a flying start – with nearly nine out of 10 people aged 80 and above, and over three-quarters of people aged 75 and over, now having had their first jab.”
Health and Social Care Secretary Matt Hancock added: “This achievement to deliver a safe, effective vaccine has only been made possible by the remarkable scientists, our dedicated care home staff and volunteers and our incredible NHS all working together.
“While we celebrate this success, we will never forget the loss of life and my thoughts are with all those who have lost someone close to them.”
Fiona Carragher, director of research and influencing at Alzheimer’s Society, said it was “great” that the milestone had been meet but remained concerned that staff vaccination rollout “has not been nearly so effective”.
“The most pressing question now is how and when can care homes restart safe, meaningful visits. Combined with PPE and testing, isn’t one jab enough? If not, what else needs to be in place? Another 12-week wait is unacceptable for people dying of loneliness,” she said.
“We need a swifter rollout of the second jab, as well as ensuring all staff receive it. At least 70% of care home residents have dementia, and they are losing their connection to the world, fading away. We must now see a concrete plan in place to reunite families.”
Liz Kendall, Labour’s shadow social care minister, said: “After the appalling loss of life in care homes it is very good news that the NHS has now offered vaccines for all elderly care home residents.
“It is essential that ministers now do everything possible to ensure care home staff take up their vaccines, move swiftly to vaccinate care homes for people with disabilities and crucially, home care staff who care for elderly and disabled people in their own homes.
“We are in a race against time against this awful virus and ministers must leave no stone overturned to vaccinate all social care staff within the next two weeks.”
Vaccinations are now being administered at more than 250 hospitals, 1,000 GP-led services, 117 high street pharmacies and 47 large-scale vaccination centres across the country.