If you need oxygen or dialysis, you can't cruise with these lines right now

If you need oxygen or dialysis, you won't be able to sail with Carnival Cruise Line, Holland America Line or Princess Cruises right now. The same goes for passengers who are unable (or unwilling) to wear masks.

According to Holland America's Travel Well FAQ and Princess Cruises' Health FAQ, the lines are "... unable to accept guests who use supplemental oxygen or are on dialysis at this time for 2021 cruises. This includes guests who use oxygen concentrators. Our medical experts have determined that, for the guest's own safety, this is the right decision. We've had to make some difficult decisions based on general public health guidelines and the overall health and safety of our guests. We remain optimistic that our approach on future sailings will become more flexible."

Carnival has similar wording on its Have Fun. Be Safe. FAQ page, as well.

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Affected passengers who are currently booked on sailings through 2021 can choose one of three options:

• A full refund of payment.
• A future travel credit worth 110% of payment.
• A rebooking for next year at the same time on the same itinerary at the same price.

Additionally, the lines -- all of which are part of Carnival Corporation -- require passengers to wear masks in indoor public areas onboard, except while eating or drinking.

"All guests will be required to wear a face mask -- with no exceptions -- in elevators and in designated indoor entertainment areas, all retail shops and in the casino except when eating or drinking," the websites state. "Guests will also be required to wear face masks prior to being seated in our main dining rooms and in the buffet area, and occasionally in other designated areas where larger number of guests may congregate."

The lines say passengers who refuse to comply could be denied boarding or disembarked at the first available opportunity, with no refund, and they will be responsible for all expenses incurred as a result.

As for other major cruise lines, Norwegian hasn't changed its policies on mask-wearing. Nor has it limited passengers with existing medical conditions under its Sail Safe protocols. It will, however, require 100% vaccination for all passengers and crew.

Royal Caribbean and Celebrity, both of which are operated by Royal Caribbean Group, have also not barred cruisers with existing conditions.

However, Royal Caribbean has tightened its vaccination policy for cruises departing from Florida. To comply with new Bahamian health requirements, the line will now require vaccination proof for anyone 12 or older who plans to sail, despite an executive order from Florida Gov. Ron DeSantis, which makes it illegal for businesses to demand proof of inoculation.

Earlier this month, a Florida court granted a preliminary injunction to Norwegian, which challenged DeSantis' order, allowing the line to make proof of vaccination a requirement for boarding.

Recently, the U.S. Centers for Disease Control and Prevention updated its cruise guidance to say, "It is especially important for people with an increased risk of severe illness to avoid travel on cruise ships."

According to the CDC, people at increased risk include the elderly and people with medical conditions (including those who require dialysis or oxygen), even if they're fully vaccinated.

The CDC has also issued a Level 3 travel health notice -- the second most severe level -- for cruisers who are not fully vaccinated.