Pharma giant Pfizer (NYSE:PFE) released its second-quarter earnings report on July 28, and the  results were impressive. Naturally, the big story surrounded the drugmaker's COVID-19 vaccine, BNT162b2, whose revenue came in at $7.8 billion for the period. BNT162b2 is the gift that keeps on giving, and Pfizer now expects total revenue of $33.5 billion from the vaccine this year, which is up from its previous guidance of $26 billion.

While Pfizer's coronavirus-related news continues to grab most of the headlines, investors should pay attention to the strength of the rest of its business. Here's one key piece of evidence from Pfizer's latest quarterly update that hammers this point home. 

Declining sales of Xeljanz

Xeljanz, a medicine indicated for the treatment of rheumatoid arthritis (RA) and plaque psoriasis, is often touted as a key growth driver for Pfizer. But during the second quarter, sales of this medicine dropped by 8% to $586 million. One of the reasons for the decline is worth noting.

Pharmacist leaning against the wall in a pharmacy.

Image source: Getty Images.

In January, Pfizer reported results from a post-marketing study for Xeljanz. The study pitted the RA medicine against TNF-inhibitors, a class of drugs that treat autoimmune disorders; this group includes AbbVie's Humira. Participants in the study were at least 50 years of age and had had at least one additional cardiovascular risk factor.

The results: Patients on Xeljanz had higher rates of cardiovascular events and higher incidences of cancer. These results did not escape the scrutiny of regulators. The U.S. Food and Drug Administration's (FDA) ongoing review of the data has had a negative impact on the number of new patients taking it, leading to lower revenue for the company's blockbuster drug.

Other avenues for growth

In the worst-case scenario, the FDA would take Xeljanz off the market on the grounds that the medicine's risks far outweigh its benefits. But this seems unlikely to happen. Still, the FDA could increase restrictions on higher doses for the drug, and label expansions are already being delayed, which is affecting sales. Even with these (potential) headwinds, though, the diversity of Pfizer's lineup mean the company's future does not depend on one single drug.

Putting aside revenue from BNT162b2, first-quarter revenue of $11.1 billion was up 10% compared to the first quarter of the previous fiscal year. For a major pharmaceutical company the size of Pfizer, a 10% year-over-year revenue increase is nothing to sneeze at. Pfizer owed this performance to anticoagulant Eliquis, whose sales of $1.5 billion jumped by 16% compared to the year-ago period.

Meanwhile, sales of cancer drug Xtandi jumped by 14% to $303 million. Inlyta, another cancer medicine, recorded $257 million in revenue, 32% higher than the second quarter of 2020. Also worth noting, Pfizer's biosimilar business saw its sales skyrocket by 93% to $559 million. Pfizer's lineup is impressive, and so is the company's pipeline, which boasts more than 50 programs.

The drugmaker had more than a dozen regulatory approvals in 2020, and that's something investors can expect the company to pull off more or less every year. In short, even without its COVID-19 vaccine, and even if Xeljanz's sales growth decreases due to safety concerns, Pfizer's business looks very healthy. 

Why you may want to buy 

Of course, when considering Pfizer's overall prospects, we can't just ignore its vaccine -- after all, the product will rack up more than $30 billion in sales in its first year on the market. The only potential downside here is that BNT162b2 is setting the bar very high. Once the pandemic subsides, don't expect it to generate that much in revenue every year. But there are good reasons to think it will continue to contribute meaningfully to Pfizer's top line. With cases of COVID-19 on the rise again, especially due to the highly contagious delta variant, the need for booster shots looks increasingly likely

That's especially true considering that BNT162b2's efficacy seems to decrease after six months. Pfizer's CEO, Albert Bourla, also thinks COVID-19 is here to stay, and the need for vaccines for the disease will become seasonal. Putting all this together, a clear picture emerges. Pfizer's business minus BNT162b2 looks strong. Pfizer's business plus BNT162b2 looks even stronger. And given that the company's shares have underperformed the market in the past year, now is an excellent time to initiate a position.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.