The latest on the coronavirus pandemic and the Omicron variant

Dean for the National School of Tropical Medicine Dr. Peter Hotez said Monday that a fourth dose of the Covid-19 vaccine would be "too late" to combat Omicron in the United States.

"By the time you get that through and get the FDA and CDC to sign off on it and by the time we get an immune response and vaccinated health care providers and that's the group I suggested that we tried it for it will be three or four weeks from now and by then possibly the Omicron wave will have subsided substantially and we'll be having to worry about the next variant," Hotez told CNN's Poppy Harlow.

Early results from an Israeli study show a fourth dose of the Covid-19 vaccine can increase antibodies, but it still not be enough to prevent Omicron breakthrough cases.

Israel began rolling out a fourth dose of the coronavirus vaccine with immediate effect for people ages 60 and over, medical workers and people with suppressed immune systems last month.

Hotez cautioned that experts in the US still need to review the final data from Israel before any recommendations on treatment.

Pfizer's Covid-19 antiviral drug Paxlovid was approved for use by Canada's health agency on Monday, officials announced during a press conference, and said the drug will be a "new tool" in the toolbox of treatment options.  

Health officials recommend that the drug, which is five-day treatment that can be taken at home, be prioritized for residents in high-risk groups with mild to moderate Covid-19 symptoms. But ultimately, provinces will make their own guidelines for distribution, they said.

Health officials said that this will include those who are moderately or severely immunocompromised and people 80 years-old and older who do not have up-to-date vaccinations, said Dr. Theresa Tam, chief public health officer of Canada. In addition, she said people who are age 60 and older who live in rural or underserved areas or are part of the First Nations are recommended for priority access. 

It will be required that anyone taking the drug have a positive Covid-19 test, either a PCR or a rapid test, and start treatment within five days of symptoms, health officials said. 

Tam said the tests will be distributed on a per-capita basis. Canada ordered an initial quantity of one million treatment doses in December, she said, but officials are still working to firm up an official delivery schedule. Regardless, the antiviral pill will be in short supply when it is first distributed as the drug is in high demand around the world, Tam said. 

Several reporters asked about concerns of long wait times for Covid-19 test results and how that might interfere with getting timely treatment, but several health officials said that they hope that those in high-risk categories are prioritized for test results and will allow quick treatment. 

Tam added that each community is going to be "a little different" in how they roll out the drug and that it is best to pay attention local guidelines. 

Health officials said that ultimately, they hope that the anti-viral will help blunt the severity of the illness and will help keep more people out of the hospital to reduce the strain on the health care system. 

Moderna should have data available on its Omicron-specific Covid-19 vaccine in March, company CEO Stéphane Bancel said Monday. 

“It should be in the clinic in the coming weeks. And we're hoping in the March timeframe, we should be able to have data to share with regulators to figure out the next step forward,” he said in a panel conversation at Davos.

“That’s always been a great partnership between public health experts, the regulators and vaccine makers to figure out what's the best path,” he said.

Many Americans can now get at-home Covid-19 tests at no cost through their private insurance. They can obtain the tests from pharmacies, retailers and online vendors.

The program, which began Saturday, is part of the Biden administration's effort to increase access to testing around the US.

But some people are having trouble getting the free tests and many Medicare enrollees are discovering that they don't qualify.

If you've tried to obtain home Covid-19 tests at no cost, share your story with us. You could be featured in an upcoming story.

Serbian tennis star Novak Djokovic has to comply with Spain's health rules to be able to compete in Madrid Open that kicks off in late April, Spanish Prime Minister Pedro Sanchez said on Monday.

Sanchez lauded Australia’s decision to deport Djokovic, saying he has "total respect for the decision of the Australian government." 

Spain currently requires visitors to show proof of full vaccination, a recent PCR negative test within 72 hours before arrival or a certificate of having recovered from Covid-19, according to its health ministry. 

International sporting events in the country may add additional rules for participants such as Covid-19 testing on a daily basis during the tournament, a senior government official told CNN on Monday.

Hear what Serbian Prime Minister Ana Brnabic had to say about Djokovic getting deported:

A vaccine mandate for those aged 60 years and is now in effect in Greece.

Greek government spokesman Giannis Oikonomou suggested the mandate had helped get that group vaccinated.

“It is important that 90%, nine out of 10, of our fellow citizens over the age of 60, have now been vaccinated. Almost half of those who were unvaccinated, when the mandate was announced, made ... the choice to get vaccinated,” he said during a news briefing.

The mandate, which came into effect midnight Sunday into Monday Greek time, does not apply to those who have exemption approval due to health reasons and does not impose fines on those who need to be vaccinated at home and are awaiting for a slot. 

Chairman of the Joint Chiefs of Staff

Gen. Mark Milley tested positive for Covid-19 Sunday and “is experiencing very minor symptoms,” Joint Staff spokesperson Col. Dave Butler said in a statement Monday. 

Milley “is working remotely and isolating himself from contact with others,” Butler said, adding that the top US general “can perform all of his duties from the remote location.” 

“He has received the Covid-19 vaccines including the booster,” Butler said.

According to the statement, Milley most recently had contact with President Joe Biden on Wednesday, Jan. 12, at Gen. Raymond Odierno’s funeral.

“He tested negative several days prior to and every day following contact with the President until yesterday,” Butler said.

“All other Joint Chiefs of Staff except for one tested negative for COVID-19 yesterday,” he said.

A combined Covid-19 and flu booster shot from Moderna could be available in some countries by fall 2023 at the earliest, CEO Stéphane Bancel said Monday.

Speaking at the Davos Agenda, a virtual event being held this week by the World Economic Forum, Bancel said this date was a “best case scenario,” but that he believed it was possible for some countries next year.

He explained it was a goal for the company to have a single annual booster shot available to avoid “compliance issues” where people are wary about getting multiple shots every winter.

Masks are to be worn outside in certain crowded areas in Paris, the prefecture police announced Monday. 

The new decree imposes obligatory wearing of masks in areas where "the density of people does not guarantee, without the wearing of masks, the proper upholding of barrier measures," the prefecture statement said, referring to acts like social distancing against Covid-19 infections. 

According to the statement, masks should be worn in outdoor markets, at rallies or gatherings of 10 or more people in public, when waiting for public transport or outside stations and malls, as well as outside teaching and cultural institutions. 

This comes after Paris’ administrative tribunal ruled on Thursday that the city-wide outdoors mask mandate was “disproportionate." Courts in the towns of Versailles and Nantes also ruled against city-wide mask mandates last week.