Both New York state and Washington, DC reported record infection numbers on Thursday.

With hard-to-find take-home tests and test requirements Creating long lines nationwide, other security measures such as wearing N95 or KN95 masks while on vacation are crucial, said Dr. Esther Choo, Associate Professor at Oregon Health and Science University.

Flying carries an increased risk due to a lack of vaccine requirements and inconsistent mask adherence, so “this could be a much safer activity than it is now,” Choo told CNN’s Laura Coates on Thursday.

“Speak out loud when you see the people around you are not wearing masks. This is not a time to be polite and let people do what they want. It’s really about protecting everyone, ”she said.

For the second Christmas in a row, hospital workers are confronted with the trauma of the death of Covid-19 patientsVaccinations and booster doses have proven to be that best method However, to prevent serious illness, the immune system needs time to respond to the doses given. And unvaccinated people – whether they see others over the holidays or not – are at a much higher risk of developing Covid-19. Approximately 71 million eligible recipients over 5 years of age in the United States have not yet received any vaccine doses. according to Data from the US Centers for Disease Control and Prevention.

More than 500 million doses of the Covid-19 vaccine have been administered in the United States, according to CDC data. Nearly 62% of Americans are fully vaccinated, and more than 34% of fully vaccinated adults have had a booster vaccination.

Travel difficulties expected

According to the Transportation Security Administration, at least 2.08 million travelers were screened at US airports on Wednesday, more than on the same day of the week in 2019. The agency expects 20 million people to fly between December 23 and January 3 which corresponds to the numbers for 2019.

However, several airlines have recently announced canceled flights and postponed flight schedules due to crew members exposed to the Omicron variant. United Airlines canceled 169 flights on Christmas Eve, or 9% of its total number of flights. according to Flight tracking page FlightAware starting Friday morning.

“The nationwide surge in Omicron cases this week has had a direct impact on our flight crews and our operation staff,” said a United memo on CNN.

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

“Delta teams have exhausted all options and resources – including rerouting and replacing aircraft and crews to cover the scheduled flight,” the airline said in a statement.

Alaska Airlines announced that it canceled 17 flights on Thursday due to Omicron and that additional cancellations are possible on Christmas Eve.

Covid-19 not only affects airport traffic. A Royal Caribbean cruise ship was recently Entry denied to Aruba and Curaçao after 55 fully vaccinated crew members and passengers – just over 1% of those on board – tested positive for Covid-19, the company told CNN. the Odyssey of the Seas has no longer scheduled ports of call and will have sea days until its regular scheduled return on December 26, Royal Caribbean said.

Researchers show that boosters and masks work

In one new paper Published Thursday in Science magazine, two infectious disease experts recommended more booster vaccinations and more mask-wearing to protect people.

The vaccine’s effectiveness wears off over time, the researchers wrote, but it can be restored with a booster dose to protect against breakthrough infections.

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“Time seems to be the number one cause of reduction in effectiveness after vaccination,” write Ravindra Gupta of the University of Cambridge in the UK and Dr. Eric Topol of the Scripps Research Translational Institute in California.

“The continued transmission in heavily vaccinated populations underscores the need to extend vaccination to all age groups while maintaining non-pharmacological measures such as wearing masks,” they write.

The researchers find that nations that were spaced apart when administering the first and second doses of the Pfizer / BioNTech and Moderna mRNA vaccines early on in vaccine adoption had longer-term persistence compared to nations like the United States and Israel immunity from the vaccinations where the vaccine doses were given three to four weeks apart.

“Giving two doses of mRNA vaccine closely spaced 3 to 4 weeks apart could have acted as a primary immunization – which induces maximally neutralizing antibodies but impairs lasting immunity,” the paper says. This suggests that the two doses of the vaccine together likely worked as the primary immunizations, rather than the first dose alone being the primary as intended.

Deflated health workers and desperate patients argue over alternative Covid treatmentsAnd while Israel has started providing a fourth dose of the Covid-19 vaccine to the elderly, said Paul Burton, chief medical officer of Moderna, in the US it will take more time to determine this waning immunity“We’ll have to wait a few more months to see how this data evolves and matures to understand when to give that extra booster dose, if necessary,” said Burton CNN’s Wolf Blitzer on Thursday, adding that he doesn’t want to downplay the importance of boosters right now.

“I think we can be confident, Wolf, that a booster vaccination will provide protection over the Christmas period and during these winter months,” he said.

Regarding a variant-specific booster that Moderna is developing, Burton confirmed that the company would begin clinical trials in early 2022, but the continued presence of two different variants could change plans.

Contributors to this report were Jacqueline Howard, Deidre McPhillips, Amanda Sealy, Michael Nedelman, Pete Muntean, Sharif Paget and Andy Rose of CNN.