A health certificate showing proof of immunity from COVID-19 will be required to enter the Vatican as of Oct. 1, the city state said Monday.

Residents, workers and visitors will have to carry the co-called "Green Pass" that is already widely used in surrounding Italy, the Holy See said in a statement.

An exception will be made for those attending mass "for the time strictly necessary for the rite."

The Green Pass — originally conceived to ease travel among European Union states —- shows that someone has been vaccinated, has tested negative or has recently recovered from the coronavirus.

On Thursday, the Italian government made it obligatory for all workers to show the certificate as of Oct. 15, in an effort to boost its vaccination campaign.