What happened

Shares of pharmaceutical giant Pfizer (PFE -0.19%) fell 10.8% in January, according to data from S&P Global Market Intelligence. The stock closed on Dec. 31 at $59.05 per share and hit its low of $49.82 on Jan. 24. It closed out the month at $52.69 and is down more than 13% this year.

So what

One of the reasons Pfizer's stock dropped was the market itself had its worst month since March of 2020, with the S&P 500 falling more than 5%. Pfizer dropped twice as much, however, because the stock's price had risen so much (more than 46% over the past 12 months), there was further to fall.

A scientist in a lab coat looks at DNA strands on a computer laptop.

Image source: Getty Images.

There were a couple of other factors that help explain the stock's drop. Late in the month, the company announced that it was ending the clinical development of vupanorsen, a drug thought to be a possible therapy to reduce cardiovascular risk from hypertriglyceridemia.

There were also concerns that the biggest drivers of Pfizer's revenue this year -- Comirnaty, its COVID-19 vaccine that it developed with BioNTech, and Paxlovid, its COVID-19 antiviral pill -- would drop once coronavirus cases fell.

Now what

The biotech company released its 2021 full-year and fourth-quarter numbers on Tuesday before the market opened. While some of the numbers came below analyst expectations, there's plenty of reason for optimism in them.

The company reported full-year revenue of $81.3 billion in 2021, up 92%, year over year. Even if you take out contributions from Comirnaty and Paxlovid, revenue would have been $44.4 billion, up 6% over 2020, Pfizer said. It posted earnings per share of $4.42, up 96%, over 2020.

The company issued revenue guidance for 2022 between $98 billion and $102 billion, including $32 billion from Comirnaty, based on contracts through January, and $22 billion from Paxlovid. In other words, Pfizer said it expects its COVID-19 franchise to produce even bigger numbers this year.

The company reported $21.9 billion in net income in 2021, enough to help it focus on developing its large pipeline that includes 89 therapies in trials, including 27 in phase 3 trials, and to look for more revenue through acquisitions. Last year, it spent $6.7 billion to buy Arena Pharmaceuticals and $2.3 billion for Trillium Therapeutics.

The company remains a favorite for dividend investors. It raised its dividend by 2.6% this year to $0.40, the 12th consecutive year it has increased its dividend. As of Tuesday's stock price, the yield was 3.12%, more than double the S&P average yield of 1.27%.