He said the move, set to take effect from October, was aimed at protecting the most vulnerable from the virus and would cover all workers employed by a care home provider.
But concerns have been raised by leaders in the care sector that such a “oppressive” approach would lead to staff shortages.
NHS figures show in Buckinghamshire, 1,033 out of 4,806 eligible staff, including agency workers, at older adult care homes had not received a first dose by June 13, 21% of all those eligible for the vaccine.
That proportion has fallen slightly from April 11, shortly after plans for mandatory vaccinations first emerged, when 25% were unvaccinated.
Vaccine hesitancy among care staff in some areas of England has prompted the decision by the Government, according to social care experts within the Scientific Advisory Group for Emergencies (SAGE).
Across the country, the uptake for first doses varies by region with London having the highest proportion of unvaccinated staff – 23%.
By contrast, 14% of care home staff in the South West and the North East and Yorkshire have not had the first jab.
In the South East, that figure is 15%
Nationally, the proportion unvaccinated is 16%.
Back in April a five-week consultation on the proposal was launched by the Department of Health and Social Care.
It has seen the idea extended to cover not only care homes for older people, but all Care Quality Commission-registered care homes providing nursing and personal care.
Making the announcement on Wednesday (June 16), Mr Hancock said “Vaccines save lives and while staff and residents in care homes have been prioritised and the majority are now vaccinated we need to do everything we can to keep reducing the risk.”
But the approach has disappointed some leaders in the care sector.
Nadra Ahmed, chief executive of the National Care Association, which represent care providers, said the Government now risked a staffing shortage.
She said: "I don't know why the Government can't carry on persuading people to have the vaccine rather than creating a legislative pathway which is so oppressive.
"The social care sector already has 112,000 vacancies and we now at risk of being left with more as some overworked, stressed and already anxious care workers have had enough."
Meanwhile, Unison general secretary Christina McAnea said: “The Government’s sledgehammer approach now runs the risk that some care staff may simply walk away from an already understaffed, undervalued and underpaid sector.”
Research published by the London School of Hygiene and Tropical Medicine found black African and mixed black African staff were twice as likely to decline a vaccination as white British and white Irish workers.
Reasons included concerns about a lack of research and distrust in the vaccine, healthcare providers, and policy makers.