Pfizer (PFE 1.24%) has become an expert at firsts. The pharmaceutical giant became the first to launch a coronavirus vaccine last year. Since then, it's scored a bunch more: bringing a COVID-19 booster to market, winning authorization for its vaccine in teens, and most recently, winning vaccine authorization for kids.

Massive revenue has followed. In fact, the company recently increased its forecast for coronavirus vaccine revenue this year to $36 billion. And Pfizer also lifted its forecast for total revenue to at least $81 billion because its other blockbusters also are growing.

At the same time, the stock has gained about 18% this year. So now the big question is: Is it too late to buy shares of Pfizer?

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A blockbuster product

First, let's take a look at Pfizer's performance now and what may be ahead. This week, Pfizer reported a 134% increase in third-quarter revenue to $24.1 billion. That includes sales of the coronavirus vaccine.

It's impossible to guess exactly how much sales of the blockbuster will grow post pandemic, but it looks like vaccine sales could remain at blockbuster levels for quite some time. Experts say the virus will be around well into the future, so we'll need protection -- and that means regular vaccinations. As we've seen through recent studies, immunity declines several months following the primary series.

Let's look at clues about future vaccine revenue from Pfizer. In its earnings call, the company said some forecasts for its 2022 vaccine revenue looked "very high," and it offered more moderate guidance. Pfizer forecasts $29 billion in vaccine revenue for 2022, based on the delivery of 1.7 billion doses.

That still is quite an impressive level. And the number could move higher. Pfizer has the capacity to produce 4 billion doses, and the company still is in discussions with governments.

Meanwhile, two elements are helping Pfizer continue to gain coronavirus vaccine market share: its booster and the use of its vaccine in kids and teens. The company's just getting started in these areas, so they clearly can drive higher orders as countries plan the number of doses needed for next year and beyond.

Rival Moderna's vaccine isn't yet available for teens and kids in the U.S. This means Pfizer has an opportunity to dominate in these age groups there.

Moving close to another victory

At the same time, Pfizer is moving closer to winning another COVID-19 market: the treatment market. The company's investigational coronavirus pill currently is in a late-stage clinical trial. The company says a data readout from the trial could come as early as this quarter. The potential pill may be a game changer because it could be prescribed as soon as an individual tests positive for COVID-19 -- and it can be taken at home.

Rival Merck, however, may be first to market with a potential pill treatment. It's already requested the authorization of its candidate. But considering the need for such a product, both companies could make billions in revenue in this area.

I've talked a lot about the coronavirus program. But Pfizer actually has many other revenue drivers today -- and potential ones well into the future. This means that Pfizer can continue to thrive, even if sales of the COVID-19 vaccine stagnate or slip.

Today's revenue drivers come in the form of seven other blockbusters. Two of those -- blood thinner Eliquis and cardiovascular drugs Vyndaqel/Vyndamax -- posted double-digit revenue growth in the third quarter. And Pfizer has 94 programs in the pipeline. Of those, 29 are in phase 3 studies. This is reason to be optimistic about the company's ability to compensate for eventual declines in the sales of its older drugs.

A bargain

As I mentioned earlier, Pfizer stock has gained this year, but the shares are trading at only about 10 times forward earnings estimates. That's a bargain, considering Pfizer's growth prospects in the near term and the long term.

Pfizer's rising return on invested capital and free cash flow are two more reasons to be optimistic about the stock.

PFE Return on Invested Capital Chart

PFE Return on Invested Capital data by YCharts.

Pfizer also is a good bet for investors looking for income. The company just paid its 331st straight quarterly dividend.

So, is it too late to buy Pfizer? Not if you're a long-term investor. Pfizer shares haven't quickly soared like the biotech companies involved in the coronavirus space. And I don't expect them to do so at any point in the future. But Pfizer has plenty of fuel to progressively grow revenue down the road -- and that should translate into steady and lasting share-price gains.