When did Antonio Vivaldi begin writing sacred vocal music?

Antonio Vivaldi made his debut as a composer of sacred vocal music in 1713.1

This opportunity arose when the choirmaster at the Ospedale della Pietà—a Venetian institution where Vivaldi served as a violin master—vacated his post, requiring the institution to seek new compositions from Vivaldi and other composers. His success in this field subsequently led to commissions from various other institutions.1