Shares of Moderna (MRNA -0.81%) were down by 5.3% as of 1:25 p.m. ET Wednesday. The company announced a long-term collaboration with Thermo Fisher Scientific to manufacture messenger RNA (mRNA) vaccines. However, that wasn't the reason why Moderna's stock price slid.
The more likely factors driving it lower were an overall stock market decline and the news that Sanofi (SNY 0.17%) and GlaxoSmithKline (GSK -0.47%) are preparing to file for regulatory authorizations of the COVID-19 vaccine they developed jointly. On Wednesday, the partners reported positive data from booster and phase 3 efficacy studies for their protein-based vaccine.
Sanofi and GlaxoSmithKline reported that the efficacy for two doses of their vaccine was 57.9%. That's well below the initial reported efficacy of 94% for a two-dose regimen of Moderna's COVID-19 vaccine, now being marketed as Spikevax. So why did Moderna's share price fall?
For one thing, Moderna's initial efficacy studies were conducted long before the advent of the now-dominant omicron variant. Sanofi and GSK said that their candidate's efficacy was "in line with expected vaccine effectiveness in today's environment dominated by variants of concern."
Also, some unvaccinated individuals have been reluctant to receive mRNA or DNA vaccines, which are based on newer technology. Protein-based vaccines have been used safely and effectively for many years to combat other viruses, including the flu, so an option of that type could be more appealing to those people.
But perhaps the biggest threat the Sanofi-GSK vaccine poses to Moderna is in the booster market. In its clinical study, participants who received a primary series of one of the already-authorized vaccines plus a Sanofi-GSK booster showed an 18- to 30-fold increase in neutralizing antibodies.
Sanofi and GSK are already in talks with the Food and Drug Administration and other regulatory agencies about submitting data to support the authorization of their COVID-19 vaccine. If the new vaccine is approved, it could negatively impact Moderna's future supply deals.