Cruise lines dropped COVID-19 rules. How did that affect cases? We got numbers from the CDC.

David Hancock spent his September vacation doing things he'd never done. He went on a cruise for the first time, hugged a sloth at an animal park in Honduras, and at some point during the trip, likely contracted COVID-19.

The 36-year-old firefighter had avoided infection for two years, but tested positive the morning after he and his wife, Melissa, who had been celebrating their 15th wedding anniversary, returned home to Savannah, Tennessee.

But not even COVID-19 could put a damper on their Royal Caribbean International sailing. "I went all that time since COVID began without getting it ... so I went and got it on a cruise ship," he told USA TODAY.

"But because I was vaccinated and boosted, my symptoms were mild," he said, adding that he would definitely go on a cruise again.

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David Hancock got up close and personal with a sloth during his September cruise.
David Hancock got up close and personal with a sloth during his September cruise.

Many recent cruise line policy changes reflect a shifting approach to the pandemic. Major cruise lines, including Royal Caribbean, Carnival Cruise Line, and Norwegian Cruise Line International dropped their vaccine requirements for many sailing in early September and eased testing rules, about two weeks before Hancock left for his seven-night voyage.

However, after the Centers for Disease Control and Prevention ended its COVID-19 Program for Cruise Ships in July and stopped updating its related webpage, COVID-19 spread amid the more relaxed approaches has been a relative mystery.

But data from the CDC obtained by USA TODAY through a Freedom of Information Act request shed some light on the numbers cruise lines reported to the agency after the rules were changed.

What COVID-19 case numbers did cruise lines report to the CDC?

The numbers also only represent new COVID-19 cases identified by positive viral tests on cruise ships entering or leaving from the U.S. The data does not show the test positivity rate or the number of passengers on the sailings.

►Norwegian began welcoming all passengers regardless of vaccination status on Sept. 3 and dropped all pre-cruise testing requirements for vaccinated passengers 12 and older. In the weeks that followed, the cruise line reported similar numbers to the weeks leading up to the rule change. The week beginning Sept. 4, the cruise line reported 138 new cases, and reported another 161 the following week. For the week of Sept. 18, two weeks after dropping requirements, Norwegian reported 204 new cases, and just 25 the following week.

The cruise line had previously reported 234, 164 and 184 cases in the three weeks leading up to the change, respectively.

►Carnival made similar changes on Sept. 6, scrapping its requirement for unvaccinated passengers to apply for a vaccine exemption and further easing its pre-cruise testing rule for vaccinated passengers on many sailings.

The cruise line reported 193 new cases for both the weeks of Sept. 11 and the following week and another 144 during the week beginning Sept. 25.

Carnival had previously reported 214, 265, and another 214 new cases in the three weeks leading up to the change, respectively, including the week of Sept. 4.

►Royal Caribbean also began welcoming all travelers regardless of vaccination status and further eased pre-cruise testing for vaccinated passengers for many sailings on Sept. 5.

The line reported 341 new cases the week of Sept. 11, and 306 the week after. The line then reported another 237 new cases for the week of Sept. 25. In the weeks preceding the change, Royal Caribbean had reported 448, 311, and 348 new cases, respectively, including the week of Sept. 4.

Dr. Peter F. Rebeiro, an assistant professor of medicine in the Division of Infectious Diseases at Vanderbilt University Medical Center, said, generally speaking, if unvaccinated passengers who test negative – as they were required to at the time – are mixed in with a mostly-vaccinated group, the "overall risk is not going to spike a huge amount," he said. However, he noted that vaccinated passengers can still spread the virus.

Rebeiro also noted that if transmission among the general population is lower at the time a passenger boards a cruise, the likelihood they will spread the virus is lower.

Anne Madison, a spokesperson for the Cruise Lines International Association, the industry's leading trade group, emphasized the safety of cruise travel.

"CLIA-member cruise lines have a strong track record for effectively managing COVID-19 by making science-driven and medically informed decisions – and continue to have health protocols in place that exceed those of nearly any other venue or travel sector outside of healthcare settings," she said in an emailed statement.

Madison added that as a condition of their membership, cruise lines must keep up certain protocols, including "maintaining elevated public health measures to mitigate the introduction or spread of COVID-19 on board ships" and sailing with high vaccination levels among passengers and crew members, among others.

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What does that mean for passengers?

The data did not show a consistent pattern in new cases for other major cruise lines, including Celebrity Cruises, Princess Cruises, or Holland America Line, either. Celebrity made similar changes on Sept. 5, while Princess and Holland America did so on Sept. 6.

During roughly the same period, the weekly COVID-19 case rate per 100,000 people steadily declined in the U.S., from 209 the week of Aug. 17 to 96.5 the week of Oct. 5, according to CDC data.

The "CDC has determined that the cruise industry has access to the necessary tools to prevent and mitigate COVID-19 on board," CDC spokesperson Tom Skinner said in an emailed statement. "While CDC provides guidance for cruise ships operating in U.S. waters under CDC’s jurisdiction, individual cruise lines will determine their own specific COVID-19-related requirements for cruise travel. Any decrease in the volume or frequency of routine screening testing of crew by cruise lines may result in lower counts of asymptomatic cases."

Victoria Alvarez knew Carnival had eased its protocols by the time she got on her Caribbean cruise in late September. Living in Florida, she said, she was used to more relaxed rules.

But the risk of getting COVID-19 did cross her mind during the trip. The 27-year-old business administration manager said the ship was crowded, particularly in the dining and entertainment venues.

Alvarez, who is vaccinated and boosted, said she and her friends took some extra precautions of their own, such as eating outside when they could and avoiding the pools, which were packed. "We just saved our swimming for the islands," she said.

"I don't know if I just haven't been in crowds like that in a while, but it was just, like, it's a lot," she added of the experience.

What precautions can people take?

Anna Bershteyn, an assistant professor in the Department of Population Health at New York University Grossman School of Medicine, said that there may be other factors the data does not reflect, "but it doesn't seem that this policy (change) had any consistent effect across cruise lines."

While there are still many COVID-19-related deaths across the country each day, she said, many people have been assessing their own risk tolerance. "It comes to this decision, what are the precautions that people should take versus going back and living life?" Bershteyn said.

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While not all passengers have felt completely safe on cruises since many lines relaxed their rules, Hancock said he and his wife are planning on taking another cruise with Royal Caribbean, even as it has further rolled back requirements.

"I feel as though COVID's not going to be going anywhere," Hancock said "It's kind of with us for the long haul. It's just a matter of preparations people take and what risks they're willing to take."

Bershteyn recommended travelers take steps to protect themselves, first by staying up to date on all the vaccine doses they are eligible for. She also recommended they make a plan with their doctor in case they do get sick, and contact the cruise line to see what options they would have.

If travelers have taken those steps, she said, she would advise travelers who want to take a cruise to go ahead. "We can't put our life on hold indefinitely, but we do want those safety nets in place in case something happens," she said.

Bershteyn also recommended travelers look for opportunities to take extra precautions when doing so "is not going to take away" from the experience, which she noted may be different for each traveler. In her case, she wears a face mask when she is in crowded places such as airports, while others may opt to eat outdoors when possible.

Have you gone on a cruise recently? What was your experience like?

This article originally appeared on USA TODAY: CDC data shows COVID-19 numbers on cruises after vaccine rules dropped