The inoculations were administered by a home doctor at Windsor Castle, a royal source said.
To avoid inaccuracies and further speculation, Her Majesty, 94, decided she would let her know she had the vaccine, the source added. Her husband is 99 years old.
The UK has reported more than 3 million cases of Covid-19 and more than 80,000 deaths, according to data from Johns Hopkins University on Saturday.
The UK reported 1,325 coronavirus-related fatalities on Friday, its highest daily increase in deaths.
In the capital, the mayor of London declared a “major incident” on Friday, warning that the city’s hospitals were about to be overrun.
“The situation in London is now critical with the spread of the virus out of control,” Mayor Sadiq Khan said in a statement.
“The number of cases in London has risen rapidly, with more than a third more patients being treated in our hospitals compared to the peak of last April’s pandemic.
“We are declaring a major incident because the threat this virus poses to our city is at a time of crisis,” Khan added. “If we do not take immediate action now, ours [National Health Service] it could overflow and more people will die. “
CNN’s Zamira Rahim and Amy Woodyatt contributed to the information.