Coronavirus updates: CDC issues stricter guidance for Thanksgiving

Wales emerged from its 17-day "firebreak" lockdown on Monday, with pubs, gyms, hair salons, restaurants and schools allowed to reopen.

But as the lockdown restrictions ended, new ones went into effect. People cannot travel in or out of the country, including to neighboring England, without a "reasonable excuse." Two households can again join together to form a bubble and meet up inside their homes. People can meet in groups of four inside cafes, bars, pubs and restaurants, which can serve alcohol until 10 p.m.

Businesses that were forced to shutter during lockdown can now reopen, while supermarkets can again sell non-essential goods. People are still required to work from home whenever possible.

Wales' First Minister Mark Drakeford called on people to be "careful and cautious."

"The fact that you can travel is not an invitation to travel and it's certainly not an instruction to travel," Drakeford said at a press conference Monday.

Drakeford said it's still too early to know whether the "firebreak" was a success but there were "tentative positive signs," including a plateauing case rate.

"We cannot go back to the way we were living our lives and throw away all that hard work," he added.

Wales' lockdown ended just a few days after England entered a month-long lockdown on Nov. 5.

Portugal began a 15-day state of emergency on Monday, with curfews imposed in the areas hit hardest by coronavirus pandemic.

From Monday until at least Nov. 23, some 7 million people across Portugal must stay at home on weekdays between 11 p.m. and 5 a.m., and on weekends after 1 p.m. Meanwhile, restaurants have to close by 10.30 p.m. on weekdays and are only allowed to provide takeaway services on weekends after 1 p.m.

Portuguese President Marcelo Rebelo de Sousa announced on Friday that the country would return to a state of emergency, which grants authorities special powers such as the restriction of movement. The decree can be extended indefinitely in 15-day periods. A state of emergency was in effect in Portugal earlier this year at the beginning of the pandemic.

The move comes as the southern European country of over 10 million people grapples with a rising number of COVID-19 cases and hospitalizations. Although Portugal has reported relatively low numbers compared with other countries in Europe -- over 179,324 total cases with 2,896 deaths -- daily infections hit an all-time high of 6,640 over the weekend.

In a promising development, an initial glimpse at the data from Pfizer's ongoing late-stage clinical trial shows that the American pharmaceutical giant's COVID-19 vaccine is more effective at preventing the disease than placebo.

A press release from Pfizer early Monday morning said the vaccine, being co-developed with Germany's BioNTech, was "found to be more than 90% effective in preventing COVID-19" according to an early analysis that included 94 confirmed cases of COVID-19 in trial participants.

"With today’s news, we are a significant step closer to providing people around the world with a much-needed breakthrough to help bring an end to this global health crisis," Dr. Albert Bourla, Pfizer chairman and CEO, said in a statement.

Vaccine experts told ABC News these results are "encouraging."

More safety data is still necessary before the company will apply for a limited authorization for high-risk individuals (i.e. elderly, health care providers and/or first responders) or the more complete Biologics License Application that grants approval for almost everyone.

Pfizer's vaccine won't be rolled out in any mass immunization campaign just yet. First, the company must demonstrate that the vaccine is not just effective but also safe. According to guidelines from the U.S. Food and Drug Administration, that means at least two months of safety data after the last injection in half the volunteers.

The company plans to submit for FDA authorization in the third week of November. From there, it could take the FDA two to four weeks to make an authorization decision after a public hearing and a recommendation from an independent vaccine advisory committee.

According to FDA guidance, companies are permitted to ask for an emergency authorization based on efficacy data from an interim analysis, plus at least two months of safety data.

This could make Pfizer the first company to have a vaccine available in the United States if given the green light by the FDA. Other companies, like Moderna, are not far behind.

Operation Warp Speed chief advisor Dr. Moncef Slaoui told ABC News that if everything continues to go according to plan and there are no major scientific or manufacturing delays, most Americans could have access to a vaccine by spring 2021 and possibly be immunized by June.

ABC News' Sony Salzman and Eric Strauss contributed to this report.

U.S. President-elect Joe Biden and Vice President-elect Kamala Harris unveiled their transition COVID-19 advisory board on Monday morning, naming the people in charge of making the rubber of the duo’s coronavirus policy hit the road as they prepare to take office in just 72 days.

"Dealing with the coronavirus pandemic is one of the most important battles our administration will face, and I will be informed by science and by experts," Biden said in a statement announcing the board. "The advisory board will help shape my approach to managing the surge in reported infections; ensuring vaccines are safe, effective, and distributed efficiently, equitably, and free; and protecting at-risk populations."

In his first address to the nation as president-elect on Saturday night, Biden said one of his first actions would be putting the panel in place -- a signal of his primary focus on getting the coronavirus pandemic in check when he takes office in January.

As previously reported, the team will be led by three co-chairs: former Surgeon General Vivek Murthy and former Food and Drug Administration commissioner Dr. David Kessler, along with Dr. Marcella Nunez-Smith, a professor of medicine at Yale University.

In total, 13 co-chairs and members comprise the board, including former director of the Biomedical Advanced Research and Development Authority (BARDA), Dr. Rick Bright, who made headlines earlier this year when he resigned from his role at the National Institute of Health and filed a whistleblower complaint over "an abuse of authority or gross mismanagement" at the U.S. Department of Health and Human Services on the COVID-19 response.

Biden and Harris will receive a briefing from the board on Monday morning, according to their transition team -- the first public event for the pair since being projected as the winners of the 2020 election.

ABC News' Molly Nagle contributed to this report.