Three Catholic doctors, including Deacon Timothy Flanigan, authored this piece, published online on the site Real Clear Science: 

Catholic churches across the country have been open for up to four months since shelter-in-place orders were lifted. With approximately 17,000 parishes in America typically holding three or more weekend masses – and a greater number of daily masses – for the last 14 or more weeks – over one million public masses have been celebrated following guidelines to prevent the spread of the virus: in sum, follow the three W’s – watch your distance, wear your mask, and wash your hands.

The Good News: for Catholic churches following these guidelines, no outbreaks of COVID-19 have been linked to church attendance, even though we have examples – some described below – of asymptomatic, unknowingly infected individuals attending mass and other parish functions. Their attendance could have led to an outbreak if appropriate precautions were not followed, yet in each case, we found no evidence of viral transmission.

…We reviewed recent public health and media reports regarding COVID-19 dissemination and found no reports of disease transmission, let alone outbreaks, in a Catholic church following such guidelines.

These findings are not surprising since wearing masks prevented all 139 clients served by two COVID-infected hair stylists from acquiring COVID-19, and these individuals were much closer to each other than socially-distanced participants at a Catholic Mass. Furthermore, a report of a mask-wearing COVID-infected individual who developed a dry cough just before a 15-hour flight with 350 passengers resulted in no other infections, even in the 25 individuals within six-feet. This demonstrates how a mask can protect those near someone who is infectious even when they have a cough.

There’s much more. Read it all. 

But the conclusion:

The data suggest that when a community follows proper guidelines, as Catholic dioceses have, people can receive the spiritual comfort of church attendance while preventing the spread of the virus.