Moderna (MRNA) shares are dropping after the pharmaceutical giant released the efficacy data for its RSV vaccine. Yahoo Finance breaks examine the reported long-term effectiveness of Moderna's latest vaccine in development.

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Editor's note: This article was written by Luke Carberry Mogan.

Video Transcript

- Let's talk about Moderna. Those shares are slipping today after the company presented stats for its experimental RSV shot that was worse than previous data. This has Wall Street analysts concerned over faster declines in the efficacy of this vaccine when compared with rival shots from Pfizer and GSK.

The shares are down some 7%. RSV is that virus that is particularly harmful for the elderly, for example, for infants. There's been some concern over the spreading of it. And indeed, these results seem to show that the further out you get from the shot, the less effective it ends up being at protecting against RSV, although it isn't clear why that happened. And it looks like people are still trying to sift through this data.

- The other headlines I was seeing today with this one this kind of patent fight they're having with Orbitz, which is really interesting, too. And it-- I guess it sounds like it's kind of concerning technology using this COVID-19 vaccine. That was also getting some real interest. And analysts were kind of trying to put some numbers around that.

For example, analysts at Bloomberg, Julie, said they think Moderna actually faces an uphill battle to avoid liability in that patent feud. So I know that was another headline making some news. Moderna, I'm just looking at the stock, down about 10% this year, down about 45% now over the past 12 months.

- Really, yes, investors are looking for more stuff from Moderna, right, more things coming to market and more revenue, which the company has said is coming.