The Vatican said Saturday that the resident of the Domus Sanctae Marthae has moved out temporarily and is in isolation, as are all the people who came into direct contact with him.
The encyclical is expected to stress the value of brotherly relations during and after the pandemic, a theme Francis evoked repeatedly during the pandemic.
A few dozen faithful, wearing masks and sitting one to a pew, attended the ceremony as part of safety measures to avoid spreading COVID-19.
Vatican spokesman Matteo Bruni has confirmed news reports earlier in the week that an official of the Holy See's secretariat of state office tested positive for the coronavirus.
The confirmed case prompted a sympathetic message from the Pope and all but emptied Saint Peter's Square.