(CNN) — As health experts warn that highly contagious coronavirus variants could soon worsen the spread in the US, the country is about to require masks on public transportation.

The pending order from the US Centers for Disease Control and Prevention comes as the country wraps up its deadliest month of the pandemic.

The CDC announced an order late Friday that will require people to wear a face mask while using any form of public transportation, including buses, trains, taxis, airplanes, boats, subways or ride-share vehicles while traveling into, within and out of the US.

The order goes into effect at 11:59 p.m. Monday.

Masks must be worn while waiting, boarding, traveling and disembarking, it said. The coverings need to be at least two or more layers of breathable fabric secured to the head with ties, ear loops or elastic bands — and scarves and bandanas do not count, the order says.

People can remove their masks briefly to eat, drink or take medication; verify their identity to law enforcement or transportation officials; communicate with hearing impaired people; don an oxygen mask on an aircraft; or during a medical emergency, the CDC’s website says.

The CDC said it reserves the right to enforce the order through criminal penalties, but it “strongly encourages and anticipates widespread voluntary compliance” and expects support from other federal agencies to implement the order.

President Joe Biden signed an executive order last week requiring interstate travelers to wear a mask, and he challenged Americans to wear masks for the first 100 days of his term.

Experts fear variants will worsen case and death tolls

Although vaccines are making their way to the public, health experts say the nation faces many more months of the pandemic, and the spread of highly contagious variants has raised alarm.

Variants such as those first identified in the UK (B.1.1.7), South Africa (B.1.351) and Brazil (P.1) are believed to be more transmissible than previous strains.

And although current vaccines are believed to be protective against them, some research has suggested they may be somewhat less effective against the B.1.351 strain.

The CDC has said the B.1.1.7 strain could become dominant in the US by March.

“The fact is, when you have a virus that has ability to transmit more efficiently than the wild type in the community, sooner or later by pure viral dynamics itself, it will become more dominant than the wild type,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said during a White House news briefing on Friday.

And more-transmissible variants such as this are likely to worsen the spread of coronavirus and add to the death toll, the Institute for Health Metrics and Evaluation at the University of Washington forecast Thursday.

The US Covid-19 death toll currently stands at more than 436,800. The model forecasts more than 594,600 total deaths by May 1 as its most likely projection — 25,000 more deaths than its previous projection.

Rapid variant spread could take that number up to 620,000 by May 1, IHME said. In a worst-case scenario, nearly 654,000 Americans could be dead of Covid-19 by May 1, IHME warned.

More than 400 cases of the B.1.1.7 variant have been reported across the US, according to the CDC. The US has identified at least two cases of the B.1.351 strain, both in South Carolina, and one case of P.1, in Minnesota.

However, experts have said surveillance for these strains has not been robust, and many more cases, especially of the B.1.1.7 variant, could be in the US.

While deaths hover near record level, another vaccine option could be near

For now, levels of daily new cases and Covid-19 hospitalizations are dipping in the US after holiday-era surges, though the number of deaths reported daily is near a record level.

• Cases: The US averaged more than 155,100 new cases a day over the last week as of Friday — 38% lower than the peak of around 249,800 recorded on January 8, according to Johns Hopkins University data.

• Hospitalizations: The number of Covid-19 patients in US hospitals on Friday was at the lowest level since December 3, at 101,003, according to the Covid Tracking Project.

• Deaths: The country has averaged more than 3,200 deaths a day across the last week — not far from the nation’s pandemic peak average of 3,357 reached on January 13, Johns Hopkins says.

Health experts have long said that high numbers of deaths can lag behind surges in cases and hospitalizations, as illnesses can last for weeks.

Meanwhile, Johnson & Johnson is preparing to seek authorization from the Food and Drug Administration next week to distribute its single-shot vaccine candidate in the US. If authorized, it would bring the number of vaccines in the US market to three.

Johnson & Johnson’s vaccine was shown to be 66% effective in preventing moderate and severe disease in a global Phase 3 trial and 85% effective against severe disease, the company announced Friday. It was 72% effective against moderate and severe disease in the US, the company said.

The vaccines already on the market in the US — two-dose products from Pfizer and Moderna — were found to be about 95% effective overall against symptomatic Covid-19, with perhaps even higher efficacy against severe cases.

While it would appear the Johnson & Johnson candidate has lower efficacy rates, it “can’t be compared head to head” against the other two, said Mathai Mammen, head of research and development at Janssen, Johnson & Johnson’s vaccine division.

That’s in part because Johnson & Johnson’s vaccine was tested later, when cases were surging even higher in many parts of the world and new variants were already circulating. And part of the Johnson & Johnson trial happened in South Africa while the B.1.351 strain was dominant there.

Health experts have told CNN that they generally think Johnson & Johnson’s vaccine would be a welcome addition in a country trying to ramp up its inoculations. Besides requiring only one shot, it also boasts potential logistical advantages: It does not have to be stored in freezers; and it can be stored for three months at refrigerator temperatures, unlike the Pfizer and Moderna vaccines.

An authorization for the Johnson & Johnson candidate would be “good news, because we urgently need more vaccine,” Dr. Peter Hotez, dean of the National School for Tropical Medicine at the Baylor College of Medicine, said Saturday.

Johnson & Johnson also is testing a two-dose regimen of the vaccine, and it could be that two doses would increase the efficacy, Fauci, the NIAID director, has said.

Boosters being developed for new strains

Some vaccine manufacturers say they are working on boosters that would address mutations. That includes Pfizer and Moderna, manufacturers of the two vaccines authorized so far in the US.

Biotechnology company Novavax, which recently reported Phase 3 trial results for its vaccine candidate in the UK and South Africa and is still conducting trials in the US and Mexico, also says it is working on a booster to protect against newly emerging strains.

Novavax started developing boosters for the newer variants this month, and said it expects to select its ideal candidates in “the coming days.”

“The company plans to initiate clinical testing of these new vaccines in the second quarter of this year,” Novavax said.

The-CNN-Wire™ & © 2024 Cable News Network, Inc., a Time Warner Company. All rights reserved.

Join our Newsletter for the latest news right to your inbox