Pfizer (PFE 1.59%) delivered plenty of good news in its first-quarter earnings report this week. The company raised its 2021 sales forecast for its coronavirus vaccine by 73%. Pfizer also lifted its annual revenue guidance -- and raised guidance excluding coronavirus vaccine sales. Investors looking for income should be happy too: Pfizer is maintaining its dividend level even after Viatris -- the result of its Upjohn spinoff -- begins paying one.

Among all of these positive points, though, one particular item stands out. Here are two clues. One: It has to do with the company's coronavirus vaccine. Two: It has to do with ensuring future revenue. And the item is...

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100 days

Pfizer is developing a regulatory pathway that would allow it to update its vaccine in a period of 100 days. The company now is testing a version of its vaccine targeting the South African variant. If the potential product and process work, the idea is that Pfizer could use this same "formula" to bring other vaccine updates to market within about three months.

This is key because it addresses one of the biggest threats to today's vaccines. Notable variants have been increasing in different parts of the world since early in the year. Those originating in Brazil, the U.K., and South Africa have drawn the most attention and concern. So far, Pfizer's vaccine has been able to handle each variant, but efficacy is lower than with the original SARS-CoV-2.

Certain mutations -- such as the U.K. one -- have become dominant in various countries. This means vaccine makers must be prepared to deal with these new versions of the coronavirus soon...and quickly.

Pfizer's goal of "100 days" could be a major step forward, especially if the company is eventually able to predict which variant(s) may be most problematic and can get to work early on a vaccine update. In such a scenario, Pfizer could launch an update before those variants gain too much ground. Ideally, we can imagine this as a process similar to that of the flu vaccine: Data is gathered regarding which upcoming influenza strains may pose a problem, and scientists update flu vaccines annually.

The revenue picture

There is a second reason this news is important. Clearly, if Pfizer can master this process and time frame, governments will continue to order the vaccine with confidence. And that represents billions of dollars in revenue for Pfizer. In its earnings report, Pfizer increased its forecast for coronavirus vaccine sales this year to $26 billion.

Even though Pfizer splits vaccine revenue with partner BioNTech, its own portion remains a big contributor to Pfizer's annual sales. The company now expects coronavirus vaccine revenue to make up 36% of its total revenue this year, up from an earlier estimate of 25%. And that's a major chunk -- especially considering that Pfizer is a big pharmaceutical company with many products. The company's ability to maintain coronavirus vaccine sales could be a significant profit driver in the years to come.

In more good news, Pfizer is getting close to making the possibility of quick vaccine updates a reality. The company says it should have immune-response data from its variant-specific candidate in early July.

At the same time, the U.S. Food and Drug Administration is supportive of vaccine developers' efforts to tackle variants of SARS-CoV-2. The regulatory agency earlier this year outlined testing procedures for vaccine updates, which apply to companies with already authorized vaccines. The FDA says it won't require massive trials for these new candidates.

What does this mean for investors? Pfizer's shares haven't been big movers on coronavirus vaccine news; the stock has only gained about 9% over the past year. But over time, the vaccine is likely to be a significant revenue and profit driver for the company -- especially if Pfizer can bring vaccine updates to market quickly.

Over time, this revenue and profit should give the shares a lasting lift. It also should support the company's policy of increasing its annual dividend. And that means long-term investors may benefit from regular income and steady share gains.