So far, Pfizer (PFE 3.64%) and Moderna (MRNA 13.67%) have fully vaccinated 69 million and 55 million Americans, respectively. That's more than 37% of the U.S. population. The companies also are vaccinating in other countries around the world, so it's fair to say they're today's coronavirus-vaccine leaders.

Vaccination has been progressing, but soon, one particular element may give vaccination rates for these two products an additional boost. And that could result in bigger vaccine orders down the road. Let's take a closer look at the news that's sure to convince many unvaccinated individuals to opt for a jab.

A person takes a selfie while receiving a vaccine.

Image source: Getty Images.

The current situation

First, let's consider the current status of the Pfizer and Moderna vaccines. The U.S. Food and Drug Administration (FDA) granted both companies Emergency Use Authorization (EUA) back in December. This means they can administer their vaccines only during this specific period of time -- when the FDA considers the need great and the situation an emergency. The agency could revoke an EUA at any time.

The FDA granted the EUAs based on early data from the companies' phase 3 trials. This includes follow up on volunteers two months after their second vaccine doses. In these situations, if the benefits outweigh the risks based on available data, the FDA is likely to issue a positive decision.

Still, some individuals have hesitated to take the vaccine without the availability of long-term data -- and full approval. This brings me to the element that could add to demand for the Pfizer and Moderna vaccines.

Both companies recently started the process to gain full regulatory approval. They've initiated rolling submissions, so Pfizer and Moderna will provide data as it becomes available rather than waiting until everything is ready and then submitting a complete file. Both are requesting priority review. That also should speed up the process.

Pfizer and its partner BioNTech say they've submitted data from a six-month follow-up on trial participants. That includes at least six months of safety data on more than 12,000 of the trial's participants. As for efficacy, Pfizer says the vaccine is 91.3% effective.

Pfizer and BioNTech announced their rolling submission in early May, and Moderna announced its submission about three weeks later. If all goes smoothly for both companies, we could imagine the FDA making the two decisions at about the same time.

An increase in vaccine demand

If the FDA grants Pfizer and Moderna full approval, I expect an increase in vaccine demand. People will see that, even after a six-month or longer period, the vaccines were safe and efficacious. This should ease the minds of individuals who worried about side effects months later or quickly waning efficacy.

Does this mean Pfizer and Moderna will see an immediate lift in sales? No. The U.S. already has purchased enough doses to cover all Americans. But an increase in people actually going out to get vaccinated is positive for future sales. If the U.S. uses up its stock of vaccines, it's likely to make another big order for the next round of vaccinations.

The number of Americans getting a jab probably will come into play when the U.S. decides on ordering booster shots. All of the people who received full vaccination will need a booster. Both Pfizer and Moderna are working on candidates. Moderna says its booster may be ready as early as this fall.

If the FDA offers Pfizer and Moderna full approval for their vaccines, the move could indeed lead to higher sales. And that's from a strong starting point. Both companies already are forecasting billions of dollars in sales for the year. Pfizer and BioNTech expect to share $26 billion in vaccine revenue. Moderna says its advance purchase agreements for the year represent $19.2 billion in product sales.

All of this means things are looking bright right now for these coronavirus vaccine companies -- and the situation will only brighten further with potential full approvals of their products.