Chief Rabbi Ephraim Mirvis added: "May Almighty God bless our Prime Minister as he battles against Covid-19 in hospital. May he be strengthened and granted a swift and complete recovery, together with all those who continue to suffer at the hands of this terrible virus."
Former Labour MP Luciana Berger wrote: "My thoughts are with Boris Johnson , his loved ones and his team at this tortuous time. I sincerely hope he makes a full and speedy recovery."
Reform Senior Rabbi Laura Janner-Klausner added that she wished the PM "a thorough recovery - from the Jewish communities."
Reports said Mr Johnson remains conscious and was moved to intensive care as a precaution should he require ventilation.
A Number 10 spokesman said: "Over the course of this afternoon, the condition of the prime minister has worsened and, on the advice of his medical team, he has been moved to the intensive care unit at the hospital.
"The Prime Minister has asked Foreign Secretary Dominic Raab to deputise for him where necessary, a request that was made before Mr Johnson was moved to intensive care."
