After Royal Caribbean’s (RCL) announcement that it was returning to international sailing in June after a year of suspended operations due to the pandemic for fully vaccinated passengers, several customers have criticized the cruise line for its decision.

Some Royal Caribbean customers are now calling for a boycott of the company on Twitter, as noted by The Daily Mail, saying that the cruise line is forcing them to get the COVID vaccine to board its ships. Last week, Royal Caribbean said it will require all passengers and crewmembers 18 and older to be fully vaccinated to board its upcoming cruises to the Bahamas and Mexico. Guests under age 18 will be required to provide a negative COVID test result.

Several users of the social media platform have slammed the cruise line for requiring the shot. One upset customer wrote they did not “want the experimental gene therapy that’s mandatory to step aboard their ships.”

The Pfizer-BioNTech and Moderna COVID vaccine has shown to be up to 95% effective in protecting against the virus in two doses of the shot, while the Johnson & Johnson vaccine has shown to have at least 66% efficacy in protecting against COVID-19.

Royal Caribbean, along with its sister cruise line Celebrity Cruises, announced the COVID vaccine requirement as it looks to make its cruise ships safer for travelers.

Cruise ships were considered breeding grounds for the coronavirus during the height of the pandemic, with many travelers stuck at sea unable to dock due to passengers and crew members being infected with the virus while onboard ships.

Royal Caribbean, and several other cruise lines, have implemented a series of safety protocols since such as requiring negative COVID tests prior to boarding to prevent infection and to keep travelers safe – all in an attempt to restart operations and to prevent the reoccurrence of superspreader events on its ships.

But some customers don’t agree with the COVID vaccine rules, saying on Twitter that the vaccine requirement goes too far. One user said, “will never sail with you again” while another said, “canceling my cruise now.”

But others applauded Royal Caribbean for its efforts, telling the cruise line “This is Awesome news!” and “I can’t wait to sail again.”

Royal Caribbean International is requiring the COVID vaccine on its seven-night Bahamas and Mexico cruises at this time, which set sail from Nassau, Florida, starting on June 12. Bookings for the cruises start on Wednesday.

The cruise line previously announced that the vaccines were required for passengers booking cruises sailing from Israel to Cyprus and the Greek Isles, starting in May.

Shares of Royal Caribbean were trading at $87.78 as of premarket hours on Tuesday, down $1.12 or 1.26%.

A proposed debt offering by Royal Caribbean Cruises will offer the latest indication of investor appetite for a hard-hit sector A Royal Caribbean cruise ship is pictured. Photo: GETTY IMAGES NORTH AMERICA / JOE RAEDLE