Pfizer (PFE -0.19%) and Moderna (MRNA 0.89%) both are nearing the finish line with coronavirus booster shots. Big pharma Pfizer said just last week that it's ready to submit its candidate to regulators in the U.S., Europe, and elsewhere in a matter of weeks. Moderna previously has said its potential booster shot may be ready by fall.

The U.S. Food and Drug Administration and the Centers for Disease Control and Prevention are saying fully vaccinated Americans don't need a booster shot right now. But with variants gaining ground, it seems clear these tools to jolt immunity higher may be necessary in the near future. Now, the big question is whether Pfizer or biotech rival Moderna will take the leading position in this new coronavirus market. Let's find out.

A healthcare worker prepares to administer a vaccine.

Image source: Getty Images.

Pfizer's strategy

Pfizer may be ahead in terms of timeframe. The company first focused on testing a third dose of its already authorized vaccine to be used as a booster six months after the second vaccine dose. This third dose isn't strain specific, of course. But it offers the body a push to produce more antibodies -- and the higher the antibody levels, the easier it is for the body to fight off infection.

Pfizer's clinical study of the third dose showed antibody levels five to 10 times higher than they were after the first two doses. The company aims to win authorization for a third dose as a booster. That's the near-term strategy. Here's the long-term strategy: Pfizer also is developing an updated version of its authorized vaccine. That candidate will target the full spike protein of the Delta variant. Pfizer plans to launch a clinical trial in August. The pharmaceutical company said in its latest earnings call that it's developing a 100-day pathway to update its vaccine as needed. This is important, considering the rapid emergence of variants.

Moderna's strategy

Moderna also is testing a third dose of its vaccine. But right away, the biotech company also started clinical trials of a strain-specific booster. In fact, Moderna is testing the following possibilities in clinical trials: a third dose of its authorized vaccine at a lower dosage; a strain-specific booster candidate targeting the South African variant; and a candidate that includes Moderna's authorized coronavirus vaccine mixed with the strain-specific candidate.

Moderna says the third dose and the strain specific booster both increased neutralizing antibody levels in a clinical trial. The company hasn't yet reported data on the combination of its vaccine with the strain-specific candidate. Moderna hasn't said how long it would take to update its vaccine or a potential booster to better tackle new variants. But the company did say the process will be quick thanks to its mRNA technology. And here's more good news from Moderna: In the most recent earnings call, CEO Stephane Bancel said the company already has signed advance purchase agreements for strain-specific boosters next year.

Which one will win?

Both companies sound strong. So, which one will dominate? Pfizer's strategy to focus on a third dose first may give it an edge. The product already showed safety and efficacy as part of a two-dose regimen. So, testing a third dose is less risky than testing a completely new candidate. And it may be easier to win authorization for another dose of a vaccine that's already been given to millions of Americans.

Of course, we still don't know if a third Pfizer dose will be recommended only for those who've already received two Pfizer doses -- or if people who've received other vaccines also may line up for a jab.

Even if authorization covers only those vaccinated by Pfizer, though, the big pharma company still may come out ahead. Pfizer has fully vaccinated more than 84 million people in the U.S. Moderna has fully immunized more than 61 million people.

But Moderna investors shouldn't fret. If all continues to go smoothly in trials, Moderna may indeed bring a booster to market by fall. So, it may lag behind Pfizer only by a few weeks. As we saw with the original vaccine, this hasn't been a problem for sales. Moderna expects orders to translate into $19.2 billion in vaccine sales this year.

So, yes, Pfizer may dominate the market. But it's very likely that Moderna's second spot will ensure it billions of dollars in revenue -- and possibly a strong share performance over time.