COVID updates: Secretary of Defense Lloyd Austin tests positive

Mondli Gungubele, the South Africa's Minister in the Presidency, tweeted some promising updates on the country's current COVID-19 surge.

The country's health department saw a 29.7% decrease in the number of new cases detected in the week ending Dec. 25 compared to the previous week.

"All indicators suggest the country may have passed the peak of the fourth wave at a national level," the minister tweeted.

South Africa was one of the first nations to record the omicron COVID-19 variant and saw cases spike in late November.

The health department said that while the omicron variant is highly transmissible, the country's hospitalization rates were lower than in previous waves.

South African officials announced they will lift several restrictions, including its curfew and crowd limits for indoor and outdoor activities.

-ABC News' Christine Theodorou

The Centers for Disease Control and Prevention (CDC) warned Americans to avoid cruises regardless of COVID vaccination status.

On Thursday, the CDC raised the health notice from a level 3 to a level 4, which is the highest level.

"Since the identification of the omicron variant, there has been an increase in the number of COVID-19 cases among cruise passengers and crew reported to CDC," the agency wrote. "Additionally, there has been an increase in the number of cruise ships meeting the COVID-19 case threshold for CDC investigation."

More than 80 cruise ships are currently being investigated or observed by the CDC after reports of COVID outbreaks on board.

In response, the Cruise Lines International Association -- the largest cruise trade association -- called the CDC's new warning "particularly perplexing" and said cases on ships "consistently make up a very slim minority of the total population onboard."

ABC News' Alexandra Faul, Mina Kaji and Sam Sweeney

COVID-19 vaccines are safe and effective in children, three new studies published Thursday by the Centers for Disease Control and Prevention find.

The first study, looking at the Pfizer vaccine in 42,000 kids aged 5 to 11 found that side effects from the shot were mostly mild and resolved within a week.

The second study, which examined data from 243 adolescents between ages 12 and 17, found the Pfizer vaccine was 92% effective at preventing COVID infection.

The final study found less than 1% of eligible children between ages 5 and 17 who were hospitalized with COVID in July and August were fully vaccinated.

"I think these studies taken as a whole confirm what we’ve been saying all along, which is that these vaccines are incredibly safe and effective," ABC News medical contributor Dr. John Brownstein, an epidemiologist and chief innovation officer at Boston Children's Hospital, said.

ABC News' Katie Kindelan

About 75% of people in the U.K. experiencing new cold-like symptoms actually have symptomatic COVID-19, a new study suggests.

Health science company ZOE, which has been conducting the ongoing study with King's College London, said the figure is based on a decline in the number of non-COVID "colds" and a sustained increase in symptomatic COVID cases.

Dr Claire Steves, scientist on the ZOE COVID Study app and Reader at King’s College London, said she wants the U.K. government's list of symptoms to be updated to include headache, runny nose and sore throat.

"The fact that 75% of new cold-like symptoms are COVID, and the classic symptoms are much less common, means the government advice needs to be urgently updated," she said in a release Thursday.

On Wednesday, the U.K. recorded a record-high 183,037 cases of COVID-19, more than double the figure reported at this time last year.