Any way you look at it, the numbers related to coronavirus vaccine candidates in development are impressive. In less than nine months, researchers have advanced 180 experimental coronavirus vaccines at least into preclinical testing. Thirty-five of those candidates are now in clinical studies, according to the World Health Organization.

The field narrows considerably, though, when we look only at vaccine candidates that have made it to late-stage testing. Currently, only three experimental coronavirus vaccines are in phase 3 clinical trials being conducted in the U.S.: 

Here's how these three coronavirus vaccines in phase 3 testing stack up against each other.

Three vaccine bottles that say Coronavirus vaccine next to a syringe.

Image source: Getty Images.

Approach 

Pfizer's and BioNTech's BNT162b2 and Moderna's MRNA-1273 use a similar approach to immunizing against SARS-CoV-2, the novel coronavirus that causes COVID-19. Both experimental vaccines rely on injecting modified messenger RNA (mRNA) into the body.

This mRNA contains instructions that direct ribosomes to build proteins that mirror the novel coronavirus' spike protein. The body's antibodies and T cells then target the spike protein. This prepares the immune system to fight off a future infection by the "real" coronavirus.

AstraZeneca and the University of Oxford took a different path with AZD1222. The vaccine candidate uses a weakened version of a common cold virus that infects chimpanzees -- adenovirus -- to deliver genetic material from the novel coronavirus spike protein. As is the case with BNT162b2 and MRNA-1273, AZD1222 spurs the body's immune system to respond and remember how to attack SARS-CoV-2 in any future infections.

Funding and supply deals

One key way to compare the three late-stage coronavirus vaccine candidates is to look at their funding and supply deals. Big money is flowing to the most promising experimental vaccines.

Moderna has received commitments of up to $2.48 billion from the U.S. government for its mRNA-1273 program. This includes a $955 million award from the Biomedical Advanced Research and Development Authority (BARDA) to develop the vaccine candidate and $1.525 billion from the U.S. government to supply 100 million doses of mRNA-1273. Moderna is also in discussions with the European Commission and the Japanese government to supply doses of its vaccine.

In May, BARDA committed to funding up to $1.2 billion for AstraZeneca's development of AZD1222. The big drugmaker signed a $750 million deal in June with the Coalition for Epidemic Preparedness Innovations (CEPI) and Gavi the Vaccine Alliance to supply 300 million doses of its coronavirus vaccine. AstraZeneca has also inked agreements with the Serum Institute of India to supply 1 billion doses for low- and middle-income countries and with the European Commission to supply up to 400 million doses for undisclosed amounts.

Pfizer and BioNTech made the decision not to accept U.S. government funding for the development of BNT162b2. However, the two companies have lined up several major supply deals. In July, Pfizer and BioNTech agreed to provide 100 million doses of their coronavirus vaccine to the U.S. government for $1.95 billion. The companies also signed deals to supply Canada with up to 100 million doses and Japan with 120 million doses. The financial terms of these agreements weren't disclosed.

Progress

Perhaps the most important criterion to use in comparing the phase 3 coronavirus vaccines is their clinical progress. On this front, one vaccine especially stands out.

Pfizer and BioNTech expect to report efficacy results for BNT162b2 by the end of October. If all goes well, this could lead to the companies becoming the first to win emergency use authorization (EUA) from the U.S. Food and Drug Administration (FDA). The FDA has indicated that it's willing to grant EUA for coronavirus vaccines even before phase 3 testing is complete.

Moderna CEO Stephane Bancel has stated in the past that his company could report interim results from the phase 3 testing of mRNA-1273 in October or November. However, those comments came before the biotech slowed down enrollment of its late-stage trials to increase the diversity of participants.

AstraZeneca was, at one point, rumored to be the lead prospect to win EUA from the FDA as early as October. However, the big pharma company paused its phase 3 trials recently after one participant experienced a severe adverse event. AstraZeneca has since resumed testing in the U.K. but still awaits approval from the FDA to restart its late-stage trial in the U.S. CEO Pascal Soriot, though, still anticipates that the company will report interim results from the phase 3 study of AZD1222 before the end of 2020.

Hot on the heels 

There's also another company that's hot on the heels of the three frontrunners. Johnson & Johnson (NYSE:JNJ) expects to start phase 3 testing of coronavirus vaccine candidate Ad26.COV2.S this month. It's possible that J&J could give the others a run for their money.

J&J is by far the largest player in the healthcare sector, so it has ample financial resources to fund the development and distribution of its coronavirus vaccine. The company already stands to receive $1 billion to supply 100 million doses of Ad26.COV2.S to the U.S. government.

Unlike the coronavirus vaccines being developed by AstraZeneca, Moderna, and Pfizer/BioNTech, J&J's experimental vaccine requires only one dose to be administered. This advantage could be enough to eventually make the healthcare giant the biggest winner of all in the coronavirus vaccine market.