Prince Philip has “slightly improved” and the Royal Family are keeping their fingers crossed, the Duchess of Cornwall has said.
The Duke of Edinburgh is being treated at St Bartholomew’s Hospital in London for a pre-existing heart condition and an infection.
He was moved there by ambulance from the King Edward VII’s Hospital on Monday.
Camilla was asked by a volunteer about the duke’s condition as she visited a vaccination centre in Croydon, south London.
She told Anne Sheehan, who works as a receptionist at the centre, that the duke’s condition has seen a slight improvement.
Buckingham Palace said after Philip was moved that the duke was comfortable, adding “doctors will continue to treat him for an infection, as well as undertake testing and observation for a pre-existing heart condition”.
The 99-year-old has spent 15 nights in hospital now – his longest ever stay.
Prince Charles visited his father on 20 February but it is not known if the duke has had any other visitors since.
Many hospitals in England have put strict rules in place regarding visitors as staff try to prevent the spread of the virus.
The Queen has remained at Windsor Castle where the couple have been spending this year’s coronavirus lockdown, alongside a reduced household of staff dubbed HMS Bubble.
The Queen and duke received their first COVID-19 vaccinations in January.
