A Pfizer's pill called Paxlovid is manufactured in Ascoli, Italy, in this handout photo.
The companies are making news in midday trading.
Pfizer shares jumped 1.9% after British regulators approved the use of Paxlovid, the drugmaker's Covid-19 antiviral pill, for people over 18 with mild to moderate illness. Paxlovid can be used for patients 12 and up with mild to moderate Covid who are most likely to end up hospitalized or not survive.
The CDC said Americans should not travel on cruises, regardless of vaccine status. Royal Caribbean dipped, as did Norwegian Cruise Line.
JMP Securities lowered the stock's rating to market perform from outperform. Consumer interest in the at- home fitness company is waning.
The oil company fell on the last day of the year. Kevin William Smith, vice president and chief technology officer, sold nearly 40,000 shares earlier this week.
Novavax's shares fell more than 2% after news that it extended manufacturing agreements with a Korean company. Emergency use authorization was granted to Novavax for its Covid-19 vaccines.
Didi fell more than 9% on Friday, continuing its decline into the end of the year. Didi went public in June, but the stock has since sunk as Chinese regulators have cracked down on the company.
CNBC's Jesse Pound and Yun Li were involved in the reporting.
