On Tuesday, Moderna (MRNA -1.22%) held its first Vaccines Day -- virtually, of course -- to give investors and analysts an overview of its pipeline of nine mRNA vaccines that it hopes will provide protection against a variety of viruses, among them SARS-CoV-2, the coronavirus that causes COVID-19. As of 3:30 p.m. EDT, shares of Moderna were up 4.6% on the day, outpacing the Nasdaq, which was up 3.9%.

The company's 259-slide presentation gave a good background on vaccines and how Moderna's vaccine-creation technology is substantially different than older technologies, but what likely drove its shares higher on Tuesday was the release of interim data from its phase 1 clinical trial testing mRNA-1893, a Zika virus vaccine. The 10 microgram dose of the vaccine produced a seroconversion rate -- patients going from not having antibodies to the virus to having antibodies -- of 94.4%. More impressive, all 23 of the patients treated with the 30 microgram dose had a seroconversion.

Moderna also tested the vaccine on patients who already had antibodies to the Zika virus: 50% of those patients receiving the 10 microgram dose and 75% of patients who got the 30 microgram dose demonstrated a four-fold increase in antibodies after the second vaccination.

Gloved hands about to give an injection into a shoulder

Image source: Getty Images.

The data clearly show that Moderna's mRNA technology can create treatments that cause patients to express viral proteins that their immune systems react to, generating antibodies.

The big questions about mRNA-1273 -- Moderna's candidate SARS-CoV-2 vaccine -- are whether the company picked the right coronavirus protein to use to generate the immune response, and whether the antibodies that are produced will actually protect patients from contracting COVID-19.

So far, 15 patients in the phase 1 clinical trial for mRNA-1273 have received the two lower doses, and enrollment for the group of 15 patients who will receive the highest dose started last week. Unfortunately, Moderna didn't release any data from that study during its Vaccines Day presentation.