For much of this year, cruise executives touted Covid-19 testing as the most important weapon in the battle against the virus.
The industry has been vocal about being the only travel segment that requires testing of every customer as well as its onboard crews.
And testing, combined with a layered regimen of protocols such as mask-wearing, social distancing and restricted shore excursions, has enabled cruise lines to resume service in small numbers in Europe and Asia.
As recently as early October, MSC Cruises executive chairman Pierfrancesco Vago, whose line was the first to restart big-ship-cruising, said, "vaccines won't be the magic wand. Vaccines will be part of the solution, but testing will be the solution."
But two months later, as vaccines begin to be distributed, some cruise CEOs are modifying their take on that.
With at least one vaccine approved and being administered in the U.K. and U.S., Royal Caribbean Group CEO Richard Fain last week said that the arrival of immunizations would change Royal's return-to-service strategy.
"Previously, we expected cruising to resume based on creating a virtual bubble of safety on a ship, even if the rest of the country was experiencing significant spread," he said in a video message to travel advisors. "Vaccines changed all that. Today we envision that the key but not the exclusive factor will be the vaccines rather than purely the protocols."
And Norwegian Cruise Line Holdings CEO Frank Del Rio said recently that the company is looking at being able to mandate immunity passports indicating either vaccination or the presence of virus antibodies.
Tom McAlpin, CEO of Virgin Voyages, which plans to launch service in May, said that while the line trusts that "we've got a process in place that will work and we can create a limited bubble, a bubble is never perfect."
He added that enforced mask-wearing and testing may be needed in the early stages of cruise resumption, but "when you have a vaccine ... it reduces the amount of controls you have to put in place."
Aside from the obvious reason for this shift -- that the vaccines are finally being distributed -- the cruise lines have perhaps been more tested by the limitations of testing than they anticipated.
When SeaDream Yacht Club became the first line to resume Caribbean cruises last month, the small-ship operator required that guests be tested twice before boarding. It didn't stop what eventually became an outbreak of seven passengers and two crew testing positive for the virus, cutting short the sailing and putting all 53 passengers into cabin quarantine for several days. SeaDream canceled the season.
Testing is not only problematic when it doesn't catch the virus. Uncruise Adventures canceled its summer season after a passenger on its first Alaska cruise tested positive for Covid-19 in August. It turned out to be a false positive, but the damage was done. The same thing happened earlier this month on Royal Caribbean International's third cruise this season out of Singapore, on the Quantum of the Seas. What turned out to be a false positive sent the ship back to Singapore early, where four subsequent tests determined the passenger was negative for the virus. But not before Royal Caribbean canceled the next cruise and had to endure two days of media questioning about the safety of cruising.
The trouble with testing
Cruise lines have carried thousands of passengers safely and without incident in Europe and Asia since August thanks to both testing and safety protocols. Because different countries have different rules, Covid cases onboard some ships in Europe were isolated and contained, preventing larger outbreaks without having to cut cruises short and cancel other sailings.
Cruise officials have been clear that there is an expectation that some Covid cases will find their way onboard, which is why they have a layered protocol approach.
Despite insisting that passengers be tested before the cruise, usually within 48-72 hours, and then are tested again at the terminal, some cases slip through because of the nature of the Covid-19 virus.
Dr. Lin Chen, director of the Travel Medicine Center at Mount Auburn Hospital in Cambridge, Mass., said, "the test is most accurate when someone has symptoms, or maybe a day before they have symptoms. During the early part of the incubation period they may not test positive. So to rely on the test alone is not a good idea."
Covid-19 test results are often described as an indication of a person's viral load at a single point in time, one that can change even hours earlier or later. Because cruise lines and some destinations ask travelers to get PCR tests two to three days prior to traveling, in theory they can be exposed in that time period, prior to leaving home or even en route. If they are, they may not have enough viral load for it to be discovered by a rapid test before boarding, especially because rapid antigen tests are less reliable than PCR tests. Although PCR tests are considered the most accurate, some studies have shown them to have false negative rates of up to 20%, meaning two out of 10 people who have Covid will test negative.
"There could be false negative and false positives, too, but the false negatives are the ones we worry about when people use that negative test to go somewhere," Chen said. "Testing is one of the measures that can help, but it's not good enough by itself."
She recommends that even travelers who test negative wear masks, use hand sanitizer and avoid crowds and large gatherings.
And as exciting as the vaccinations are, Chen said it will still be a while before those other protocols aren't in use.
"We still need to continue to take all these precautions, like wearing masks and some social distancing, until a really large part of the population is vaccinated," she said. "Will it then allow us to travel freely? I think it will have a huge, huge impact in leading us to restart travel again and restarting safely."