What happened

In contrast to the broader stock market and many fellow healthcare companies, Pfizer (PFE 0.91%) stock had a fine Wednesday. The high-profile pharmaceutical giant's shares coasted more than 3% higher while the S&P 500 index slumped by nearly 0.3%. There were several reasons why Pfizer managed to float above the market that day.

So what

Pfizer has numerous tailwinds going for it, not least its continued leading position in the fight against COVID-19. The company's Comirnaty vaccine, developed in partnership with German biotech BioNTech (BNTX 0.29%), remains a go-to jab at a time when the weather is getting colder and case numbers are rising.

A smiling doctor in the middle of a consultation.

Image source: Getty Images.

Meanwhile, on Wednesday Pfizer announced a potentially big advancement in another major segment of healthcare, oncology. The company said it has closed the acquisition of Trillium Therapeutics, a clinical-stage biotech developing several treatments for cancer.

In late August, Pfizer revealed it had struck a deal to acquire the company for $2.26 billion in cash. Many investors welcomed the buy and obviously continue to do so, as Trillium's pipeline meshes very well with Pfizer's current efforts in the oncology space.

Another development for the big pharmaceutical company is that its CFO is retiring. It said on Wednesday that Frank D'Amelio -- who also serves as the company's executive vice president of global supply -- is exiting after nearly 15 years in its ranks. Pfizer said it has launched an external search for a new CFO, and tapped its current president of global supply Mike McDermott to take on the latter position.

Now what

To sum, Pfizer's latest developments include the closing of a deal for a highly complementary asset, and a smooth transition in the upper managerial ranks. It's no wonder investors were bullish on the stock Wednesday.