Six more U.S. states confirmed infections of the Omicron variant of COVID-19 on December 3, but the Delta strain likely remains a greater threat as winter sets in and Americans gather for the holidays, experts said.

The U.S. Food and Drug Administration approved Merck’s anti-PD-1 therapy Keytruda for the adjuvant treatment of adult and pediatric (12 years and older) patients with stage IIB or IIC melanoma following complete resection. Additionally, the FDA expanded the indication for Keytruda as adjuvant treatment for stage III melanoma following complete resection to include pediatric patients (12 years and older).

Less than three months after Swedish Orphan Biovitrum AB (Sobi) agreed to be acquired by Advent International and GIC Special Investments for nearly $8 billion, the deal fell through after AstraZeneca withheld the company’s 8 percent stake from the buyout offer.

The Omicron variant of the virus that causes COVID-19 likely acquired at least one of its mutations by picking up a snippet of genetic material from another virus – possibly one that causes the common cold – present in the same infected cells, according to researchers.

The U.S. health regulator added the FDA’s strictest warning to the labels of drugs from Pfizer, Eli Lilly and AbbVie belonging to a class of anti-inflammatory treatments called JAK inhibitors, citing risk of serious health issues and death in patients 50 and over, the drugmakers said on December 3.

COVID-19 vaccine makers have contingency plans to deal with the Omicron variant that include a combination vaccine against the original version and the variant as well as a variant-specific booster dose, a top U.S. health official said on December 3.