The Archbishop of Canterbury said on Monday he would miss a national service of thanksgiving for Queen Elizabeth II's platinum jubilee after testing positive for Covid.
Justin Welby, who leads the Anglican Communion around the world, said he was "deeply saddened" at the missing Friday service at St Paul's Cathedral in central London.
He was diagnosed with mild pneumonia on Thursday and developed symptoms of the coronavirus over the weekend and has canceled all events this week.
"However, I will pray for the Queen and thank all of us for the exceptional service of 70 years," said the Archbishop.
"I too am praying for our nation in this time of celebration and thanksgiving. May the Queen's example bring us together in unity and care for one another."
The Church of England's second-highest-ranking cleric, Archbishop Stephen Cottrell of York, will deliver the sermon instead.
Buckingham Palace has yet to confirm whether the 96-year-old monarch himself will attend the Anglican service.
She has restricted her public engagements in recent months after complaining of mobility problems. He contracted Covid-19 in February.
The two figures scheduled to attend Friday are Prince Harry and his wife Meghan, according to his biographer, Omid Scobie.
The Duke and Duchess of Sussex stepped down from royal duties and moved to North America in early 2021. After a series of disputes with the royal family, he has only visited the UK once.