The big question these days is this: Do we need coronavirus booster shots right now? U.S. health authorities weighed in with a "no" earlier this month. The Centers for Disease Control and Prevention and the U.S. Food and Drug Administration (FDA) in a joint statement said those who are vaccinated are protected against severe illness -- even illness caused by the highly transmissible delta variant.

At the same time, vaccine leader Pfizer (NYSE:PFE) aims to apply for Emergency Use Authorization of its booster in August. (The booster is a third dose of its authorized vaccine.) Can regulators possibly change their minds and give Pfizer the go ahead? Well, four words from Pfizer CEO Albert Bourla signal the authorization of a booster shot may be right around the corner -- in spite of health authorities' recent statement.

A doctor wearing a mask and face shield vaccinates a patient.

Image source: Getty Images.

January and February vaccinations

"The clock is ticking," Bourla said during the Pfizer earnings call this week. He referred to countries that vaccinated heavily in January and February.

Pfizer considers a booster is needed six to 12 months after full vaccination for maximum protection against coronavirus. Especially considering the presence of the delta variant. This means that for people vaccinated early in the year, the ideal time for the booster is right now.

Israel aggressively vaccinated early on. And the country today is rolling out its booster program. The plan is to offer third doses to everyone age 60 and older.

Now, let's look at U.S. vaccination trends. Vaccine administration peaked on April 8, with more than 4 million doses administered daily. But vaccinations actually were already happening at a healthy rate as of late February. By then, vaccinations had reached more than 3 million doses administered daily.

It's fair to say a good share of Americans went for a jab between February and April. And that means they're due for a booster between now and October.

The data supports that timeline. Israel has relied on Pfizer for its vaccination program. And the country has been carefully tracking performance. Israel's most recent real-world data show the vaccine's efficacy dropped to 39% in coronavirus prevention. Again, it's important to keep in mind that most people received the vaccine early in the year.

The good news

But here's the good news. It looks like the booster can set things right. Pfizer estimates a 100-fold increase in neutralizing antibody levels after the third dose compared to before the third dose. That's in people who received full vaccination more than six months earlier. Neutralizing antibodies are key to blocking the virus. 

The U.S. vaccination timeline and booster data back up Bourla's comment. That means a booster should be imminent. But there is one final factor that enters the mix. And that's the word from U.S. health authorities. As mentioned earlier, they aren't yet ready to recommend a booster.

Should Pfizer and Pfizer's investors worry? Not necessarily. Pfizer hasn't yet submitted booster data to the FDA. Regulators may change their view on the timing of a booster after examining Pfizer's trial results. And the coronavirus situation is rapidly evolving. For example, the seven-day moving average of cases was about 13,400 on June 30. Today, it's at more than 66,000. A statement made in early July might no longer apply a month later.

Of course, it's impossible to predict whether the FDA will give Pfizer the nod for a third-dose booster. But the overall picture supports Pfizer's case.

So, what happens if and when a third dose wins authorization? The potential authorization of a booster isn't likely to add to revenue immediately. The U.S. just placed an order for an additional 200 million Pfizer vaccine doses to be delivered through April of next year. That brings the total U.S. order so far to 500 million doses. If the FDA authorizes a third dose, this existing supply likely will suffice for now.

But, the need for three doses instead of two may lead to bigger orders down the road. And that means Pfizer's days of growing vaccine revenue have only just begun.

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.