From wikipedia:

On 9 January 2021, Philip and the Queen were vaccinated against COVID-19 by a household doctor at Windsor Castle.[137] On 16 February 2021, Philip was admitted to King Edward VII's Hospital as a "precautionary measure" after feeling unwell.[138] He was visited by Prince Charles on 20 February.[139] On 23 February, it was confirmed by Buckingham Palace that Philip was "responding to treatment" for an infection.[140][141] On 1 March 2021, Philip was transferred by ambulance to St Bartholomew's Hospital to continue treatment for an infection, and additionally to undergo "testing and observation" relating to a pre-existing heart condition.[142] He underwent a successful procedure for his heart condition on 3 March,[143] and was transferred back to King Edward VII's Hospital on 5 March.[144] He was discharged on 16 March.[145]