Pfizer (PFE 3.94%) stock has been in the dumps this year. It is struggling due to declining demand for its COVID products. And it may take some years before its top line starts rising meaningfully again. The company's recent forecast didn't help matters, either. But with the stock losing close to half its value this year, are investors being overly punitive on what's still a top healthcare company?

Pfizer's top line may decline in 2024

On Dec. 13, Pfizer unveiled its forecast for the coming year, and to say it wasn't an exciting one would be an understatement. For 2024, the company projects that its revenue will be within a range of $58.5 billion to $61.5 billion. And this even includes revenue it will generate from its recently closed acquisition of cancer company Seagen, which is no small operation -- Pfizer projects that Seagen will add $3.1 billion in revenue next year.

This year, the company projects its revenue to fall within a range of $58 billion to $61 billion. That means that Pfizer's business would likely experience a decline in revenue next year, if not for its recent acquisition. The best-case scenario for the company is that its revenue stays flat or achieves a modest increase in 2024. A year ago, Pfizer reported a record-breaking $100 billion in sales due to surging revenue from its COVID vaccine and pill.

A slowdown was inevitable

While the forecast is underwhelming, it also shouldn't come as a big surprise to investors. COVID isn't striking fear into people the way it was even a year ago. Demand for vaccines has been diminishing, and Pfizer investors have already been seeing the effects of that on the company's financials.

Year to date, Pfizer's global revenue of $21.8 billion has declined 48% from the same period in 2022. A big part of the reason is that Comirnaty, the company's COVID vaccine, has experienced a 78% decline in sales.

Next year, Pfizer is projecting that revenue from Comirnaty and Paxlovid (its COVID treatment) will still bring in $8 billion. That's the part of the forecast that may be concerning as demand for COVID vaccines and treatments has proven to be difficult to predict. But an overall slowdown in the business shouldn't be surprising for Pfizer investors.

Have investors overreacted?

Pfizer's stock fell by nearly 7% after the company released its forecast. It has bounced back since then, but that may have more to do with the rally in the markets of late. Year to date, it is still down more than 45%. The stock is trading at just 10 times based on its future profits (based on analyst estimates). That suggests investors aren't overly optimistic about the company's future.

However, Pfizer has been planning for growth in the long term. The company plans to add $25 billion in new additional revenue by 2030, with acquisitions such as Seagen playing a key part of that strategy. That will help in offsetting a decline in revenue from drugs losing patent protection and facing increased competition in the years ahead. But it won't be enough to get the company back to generating $100 billion in sales. The important takeaway for investors is that Pfizer is making efforts to grow its business, which means that in the long haul, this could still be a good growth stock to own.

Should you invest in Pfizer's stock?

Pfizer has the potential to be one of the most undervalued stocks heading into next year. With the shares trading at a low multiple of earnings, investors have a good margin of safety with the stock in the event that it does worse than analysts expect next year. The average healthcare stock trades at more than 20 times its estimated earnings.

As long as you're willing to be patient, Pfizer could be a good healthcare stock to add to your portfolio and hang on to for the long term.