(CNN) – With holiday travel returning to pre-pandemic levels, a health expert is giving advice to those planning to visit loved ones at Christmas, given the spike in COVID-19 cases in many parts of the country.

New York and Washington state both set infection records on Thursday.

Given the difficulty of finding tests to take home and the demand for tests creating long queues across the country, other safety measures such as using N95 or KN95 masks while vacation travel will be necessary, said Dr. Esther Chu, associate professor at Oregon Health University. and science.

CNN’s CNN’s Laura Coates said Thursday that flying is more risky due to a lack of vaccine requirements and a lack of consistent commitment by some to fully maintaining their masks, so “this could be a much safer activity than it currently is.”

He said, “Report when you see people around you not wearing masks. This is not the time to be polite and let people do what they want. It’s really about keeping everyone safe.”

Vaccines and booster shots have proven to be the best way to prevent serious diseases, but immune systems take time to respond to the doses given. And people who haven’t been vaccinated, whether or not they see other people on vacation, are at high risk of getting seriously ill from COVID-19.

About 71 million people age 5 and older in the United States have not yet received any doses of the vaccine, according to data From the US Centers for Disease Control and Prevention (CDC).

More than 500 million doses of the COVID-19 vaccine have been administered in the United States, according to data from the Centers for Disease Control and Prevention. Nearly 62% of Americans have been fully vaccinated, and more than 34% of fully vaccinated adults have received a booster dose.

Travel difficulties are to be expected

At least 2.08 million passengers were screened at US airports on Wednesday, up from the same day of the week in 2019, according to the Transportation Security Administration. The agency predicts that 20 million people will travel by air between December 23 and January 3, which rivals 2019 figures.
However, several airlines have recently announced flight cancellations and schedule changes due to the exposure of crew members to the omicron variant.

United Airlines has canceled 169 flights on Christmas Eve, or 9% of its total, according to flight-tracking website FlightAware as of Friday morning.

“The increase in Omicron cases across the country this week has had a direct impact on our flight crews and the people who run our operation,” says a US memo obtained by CNN.

Delta Air Lines canceled 118 flights on Christmas Eve, according to FlightAware, about 5% of its total schedule.

“Delta teams have exhausted all options and resources, including changing the route and replacing aircraft and crew to cover scheduled flights,” the company said in a statement.

Alaska Airlines announced that it canceled 17 flights Thursday due to Omicron and there may be more cancellations on Christmas Eve.

But the coronavirus doesn’t just affect flights to the airport. The company told CNN that a Royal Caribbean cruise ship was recently denied entry to Aruba and Curaçao after 55 fully vaccinated crew members and passengers (slightly more than 1% of those on board) tested positive for covid-19.

Royal Caribbean said Odyssey of the Seas no longer has scheduled ports of call and will have days at sea until its regular return on December 26.

Researchers have shown that masks and masks work

In a new article published Thursday in Science, two infectious disease experts are recommending more booster injections and more use of masks to protect people.

The effectiveness of the vaccine decreases over time, according to the researchers, but it can be restored with a booster dose to help protect against last-minute infection.

“Time appears to be the main factor in reducing efficacy after vaccination,” wrote Ravindra Gupta of the University of Cambridge (UK) and Dr Eric Topol of the Scripps Institute for Translational Research (California).

“Continued transmission in a heavily vaccinated population underscores the need for increased vaccination across all age groups, while maintaining non-pharmacological interventions, such as the use of masks,” they wrote.

The researchers noted that early in the vaccine introduction, countries that diverged between the first and second doses of Pfizer/BioNTech and Moderna mRNA vaccines experienced greater robustness of injection immunity, compared to countries such as the United States and Israel, where doses of the vaccine were given three to four intervals weeks.

The research paper notes that “administering two doses of mRNA vaccine, 3-4 weeks apart, may act as a primary immunization, increasing neutralizing antibodies but detrimental to long-term immunity”. This indicates that two doses of the vaccine together are likely to serve as the initial immunizations, rather than the first dose alone being the primary dose as intended.

As Israel begins providing a fourth dose of the COVID-19 vaccine to elderly people, Moderna’s chief medical officer, Paul Burton, said more time is needed in the United States to determine the decline in immunity.

“We still have to wait two months, until we can see how this data develops and matures to understand when the additional booster dose should be given, if needed,” Burton told CNN reporter Wolf Blitzer. Thursday, adding that he did not want to downplay the importance of reinforcements at this point.

“I think we can be sure, Wolf, that getting a booster shot will provide protection during the holiday season and during the winter months,” he said.

As for the specific enhancement of the variant that Moderna is developing, Burton confirmed that the company will begin clinical trials in early 2022, although continued presence of two different variants could derail plans.

CNN’s Jacqueline Howard, Deidre MacPhillips, Amanda Seely, Michael Needleman, Pete Montaigne, Sheriff Paget and Andy Rose contributed to this report.