I'm not afraid of receiving a shot, but I haven't exactly looked forward to getting one. Until recently.

Several days ago, I received my second dose of BNT162b2, the COVID-19 vaccine developed by Pfizer (PFE 0.31%) and BioNTech (BNTX 0.86%). I've never been more excited and appreciative to have a needle jabbed into my arm. My hunch is that millions of Americans and people throughout the world experienced a similar feeling.

Pfizer's and BioNTech's vaccine has been a phenomenal success story, from the breathtakingly fast development to the jaw-dropping efficacy. And now there's even more good news. Here's why Pfizer's and BioNTech's COVID vaccine could be even better than expected.

Gloved hands holding a syringe and needle with a vaccine vial

Image source: Getty Images.

A variant victory

Last week, Pfizer and BioNTech announced updated results from their late-stage study that served as the basis for winning Emergency Use Authorization (EUA) for BNT162b2. Probably the most surprising new information from those results was that the vaccine was 100% effective in preventing COVID-19 in South Africa, where a coronavirus variant named B.1.351 is running rampant.

Some health experts have expressed concerns that the currently available COVID-19 vaccines might be much less effective against new variants of concern -- and especially B.1.351. Studies conducted in labs found that the Pfizer-BioNTech vaccine, and the COVID-19 vaccine developed by Moderna, produced much lower levels of neutralizing antibodies with the South African variant than they did with the dominant coronavirus strain.

Pfizer, BioNTech, and Moderna took this threat seriously. The companies initiated new clinical studies to evaluate booster doses of their vaccines in protecting against new coronavirus variants.

The latest results from Pfizer and BioNTech, though, are encouraging. Millions of people vaccinated with BNT162b2 might be more protected from the South African variant than originally thought.

However, the late-stage study conducted by Pfizer and BioNTech included only 800 participants in South Africa. Nine cases of COVID-19 occurred, with all of the cases in the study's placebo group. Six of those nine cases were confirmed to be of the B.1.351 variant lineage. It's possible (and arguably even probable) that in a study including a larger number of participants, BNT162b2 wouldn't be 100% effective in preventing infection by the South African variant.

The rest of the results

Pfizer and BioNTech also reported that BNT162b2 achieved 91.3% overall efficacy up to six months after the administration of the second dose. You might wonder if this should be viewed as bad news, since the vaccine's initially reported overall efficacy was 95%. Actually, it's good news.

The companies' first results evaluated efficacy relatively soon after participants in the late-stage study received their second dose. Based on Pfizer's and BioNTech's updated results, it appears that there isn't much degradation of protection against infection several months later.

Perhaps the best news is that BNT162b2 continued to be highly effective at preventing severe disease. Pfizer and BioNTech reported that the vaccine was 100% effective in preventing severe disease based on the U.S. Centers for Disease Control and Prevention definition, and 95.3% effective in preventing severe disease based on the U.S. Food and Drug Administration definition.

Better-than-expected sales?

With governments across the world concerned about the B.1.351 variant, the latest news from Pfizer and BioNTech could translate to better-than-expected sales for BNT162b2. In February, Pfizer projected the vaccine would generate sales of around $15 billion based on supply deals in place at the time. Since then, though, Pfizer and BioNTech have secured more large supply agreements.

BioNTech stated in its fourth-quarter update on March 30 that its revenue from BNT162b2 this year should total 9.8 billion euros (around $11.5 billion). Pfizer and BioNTech share profits from the vaccine equally, so total revenue of around $23 billion for the vaccine appears to be on the way. Again, though, BioNTech's projection was based on the supply deals in place then.

BNT162b2 doesn't have to ultimately prove to be 100% effective at providing protection against the South African variant. However, if it's highly effective against that variant, there's a pretty good bet that Pfizer and BioNTech will pick up even more supply deals with other countries. They'll probably also receive reorders for next year from the U.S. and Europe.

BioNTech's shares have already soared more than 30% so far this year thanks to the success of BNT162b2. It's been a different story for Pfizer, though: The big pharma stock is down a little year to date. With the company's latest good news potentially pointing to higher sales, I think Pfizer's share price is due for a nice shot in the arm.