The latest on the coronavirus pandemic and vaccines

Facing a surge in Covid-19 cases, Cuban officials Tuesday night said they are implementing new restrictions, including shutting schools in much of the capital Havana and other parts of the island.

Cuban health officials on Tuesday reported 487 new Covid-19 cases, topping the previous record set the day before.

Schools will be shut in 34 municipalities hard hit by the pandemic starting on Thursday, officials said.

Cuba has recorded more than 15,000 coronavirus cases, including 155 deaths, according to Johns Hopkins University.

For much of the pandemic Cuba had managed the outbreak more effectively than many other countries in the region but since reopening borders in late 2019, the communist-run island has seen a sharp increase in infections.

Officials said Tuesday more restrictions would be put into place soon on transportation and commerce.

China recorded its highest daily increase in Covid-19 cases in more than five months on Tuesday, following a recent cluster of infections in the northern Hebei province.

The National Health Commission said in a statement that the country reported 115 new confirmed cases Tuesday, which is the highest daily rise since July 30.

Hebei's vice governor Xu Jianpei announced Tuesday that a second round of mass testing programs would kick off in the cities of Shijiazhuang, Xingtai, and Langfang. The first saw 17 million people tested in the province in a program that ended on Sunday.

The number of new asymptomatic cases, which China does not classify as confirmed cases, was 38.

China has recorded a total of 87,706 confirmed cases during the pandemic and at least 4,634 people have died.

A Covid-19 vaccine developed by China’s Sinovac Biotech was just 50.38% effective in late-stage trials in Brazil, significantly lower than earlier results showed, according to a statement published by the government of São Paulo Tuesday.

While the number meets the threshold required by global regulators for approval, it falls far below the 78% figure announced last week.

It's raising questions as to the veracity of the data and fueling skepticism over the apparent lack of transparency regarding Chinese vaccines.

The razor-thin results for regulatory approval are likely to lead to concern among scientists, given that last week the Brazilian Institute released partial “clinical efficacy” results celebrating 78% to 100% efficacy in preventing infections. The vaccine was studied in 12,500 volunteers, all of them health professionals, across Brazil.

Why the data changed: In a summary of the clinical study published by the government of São Paulo and the Butantan Institute, data for another group of participants who reported “very mild” cases of infection was included, therefore yielding a lower efficacy rate for the vaccine.

Questions over efficacy: However on Tuesday, high-ranking members of the Brazilian Health Ministry told CNN affiliate CNN Brasil that "the effectiveness is borderline," and that because "it is at the limit" they would need the county’s health regulator agency, ANVISA, to evaluate.

A representative of Sinovac said the company is discussing the result but declined to give further comment. 

Last week, ANVISA told the Butantan Institute that in order to approve the emergency use of a vaccine, the global efficacy rate had to be disclosed to the public -- information the institute did not receive from Sinovac at the time, according to CNN Brasil sources.

Scientists have identified an "escape mutant" that may decrease the efficacy of Covid-19 vaccines.

The mutation -- called E484K -- has been found in a variant of the coronavirus first spotted in South Africa two months ago. That variant has now spread to 12 other countries.

Penny Moore, associate professor at the National Institute for Communicable Diseases in South Africa, called the mutation "alarming."

E484K is called an "escape mutant" because it's been shown it might be able to escape some of the antibodies produced by the vaccine.

"I'm worried," said Alex Sigal, a virologist at the Africa Health Research Institute.

Sigal, Moore, and other scientists who are studying the E484K mutation still have to complete their work in the lab to see if the vaccine is less effective against this new variant.

Based on what they've seen so far, they say they highly doubt E484K will render the coronavirus vaccines useless. Rather, they think there's a possibility the mutation -- on its own or in combination with other mutations -- could decrease the efficacy of the vaccine against the variant.

They also worry E484K might be an indication the novel coronavirus is showing its ability to change before our eyes. If this mutation happened in a matter of months, other problematic mutations could follow.

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Scientists fear the 'escape mutant' in coronavirus variant from South Africa

The US Centers for Disease Control and Prevention said Tuesday it will require a negative Covid-19 test from all air passengers entering the United States -- a move it says may help slow the spread of the coronavirus.

Air passengers will be required to get a viral test within three days before their flight to the US departs, and to provide written documentation of their lab results, or documentation of having recovered from Covid-19, the agency said in a statement to CNN.

CDC Director Dr. Robert Redfield is expected to sign the order on Tuesday and it will go into effect on January 26.

If a passenger does not provide documentation of a negative test or recovery, or chooses not to take a test, the airline must not allow the passenger to board, the CDC said.

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CDC to require negative Covid-19 test for international passengers flying to US

More than 9 million people have received the first shot of their coronavirus vaccine and more than 27 million doses have been distributed, the US Centers for Disease Control and Prevention said Tuesday.

The CDC’s regular report on vaccine distribution and administration shows 27,696,150 vaccine doses have gone to states and territories and 9,327,128 shots have gone into people’s arms. That means one-third of vaccines that have been delivered have been given to people.

The CDC said 951,774 residents of long-term care facilities have been vaccinated, with nearly 4.4 million doses sent out to the facilities -- which were designated to be the first sites covered under vaccine rollout.

Officials of Operation Warp Speed defended the slow rollout of vaccines on Tuesday, saying states were sticking too rigidly to guidance designating health care workers and nursing home residents to be vaccinated first. They said the rollout would speed up soon and asked states to open up vaccination to everyone 65 and older and to younger people with chronic conditions.