The US Centers for Disease Control and Prevention approved the plan.
This closely follows Celebrity Edge, set to become the first oceangoing cruise ship to begin service from the US mainland, on June 26.
With this announcement, nine of Celebrity's 14 ships are scheduled to be carrying passengers by mid-September in the Caribbean, Europe, Alaska and the Galápagos.
95% vaccination status
At least 95% of crew and passengers carried by Celebrity Equinox will need to be vaccinated for COVID-19. As of Aug. 1, all passengers ages 12 and older must be vaccinated.
Celebrity Equinox will sail a seven-night itinerary to Cozumel, Costa Maya and Nassau.
Celebrity Millennium became first in the fleet to carry passengers when it embarked in St. Maarten on Saturday.