What happened
Shares of Moderna (MRNA 0.51%) were falling 4.7% lower as of 11:55 a.m. EDT on Wednesday. The decline came after the company reported that the first participant has been dosed in a phase 1/2 study evaluating its quadrivalent flu vaccine. However, the more likely reason for the stock slipping is that investors remain concerned about the potential impact of the coronavirus delta variant on sales of Moderna's COVID-19 vaccine.
So what
Moderna's announcement about the first patient dosing with its experimental flu vaccine is good news. This could easily have served as a positive catalyst for the vaccine stock were it not for other worries on investors' minds.
Image source: Getty Images.
There really hasn't been any bad news for Moderna itself with respect to new coronavirus strains, including the highly contagious delta variant. However, Israel's Health Ministry recently reported significantly lower efficacy for the COVID-19 vaccine developed by Pfizer (PFE 0.21%) and BioNTech (BNTX 2.35%), with this decline likely due to the delta variant.
Both the Pfizer-BioNTech vaccine and Moderna's vaccine use messenger RNA (mRNA). Because of the similar approach, it's possible, if not probable, that Moderna's vaccine could also be less effective against the delta variant.
It's important to note, though, that the Pfizer-BioNTech vaccine still had an efficacy of 64% in the real-world data compiled by the Israeli government. That means that the vaccine can still prevent the spread of COVID-19. Also, the vaccine was 93% effective in preventing hospitalizations and severe disease.
Now what
Moderna is evaluating a variant-specific booster vaccine in a clinical study. With the rise of the delta variant, the results from this study could be key to the company's fortunes going forward.
