Moderna (MRNA 13.53%) has lost a lot of its luster from a stock performance point of view. The shares have slipped more than 30% since the start of the year. Until recently, that didn't accompany any particularly bad news. Moderna continued to advance candidates in the pipeline. And it continued to report billions of dollars in sales and profit thanks to its coronavirus vaccine.

Recently, though, Moderna said something that isn't exactly the best news for one of its programs. In fact, it may be rather negative. Now, the question is: How bad is this news? And should it prompt you to flee this biotech stock? Let's take a look at what happened -- and what it means for the stock.

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Closest-to-market candidates

Today, Moderna's only commercialized product is its coronavirus vaccine. But the company is working to add others as quickly as possible. And some of its closest-to-market candidates are in Moderna's coronavirus program. It's working on strain-specific boosters, for example. They're in phase 2 trials. Moderna also has its eye on what could become the source of recurrent coronavirus vaccine revenue. And that's a combined flu/coronavirus vaccine. About 50% of Americans went for a flu shot last year. The idea is this population could easily opt for such a product.

Now, to make this type of shot, you need a coronavirus vaccine and a flu vaccine. Moderna has the COVID-19 one in fully developed and commercialized form. But the company's flu program is rather early stage. Moderna must show its flu vaccine candidate is safe and effective in clinical trials -- and then it can combine it with the coronavirus element and start trials on the combination candidate.

Here's where the bad news comes in. Moderna recently reported interim data from a phase 2 study of its flu candidate mRNA-1010. Side effects were much more common in participants who received the Moderna candidate versus those who received approved flu shot Afluria. For example, in the 50 to 64 age group, 31.6% of participants experienced side effects after Afluria -- that's compared to more than 68% for those who took the Moderna jab.

Setting up a challenge

This doesn't mean mRNA-1010 is a failure or won't make it into a potential combined vaccine. But it sets Moderna up for a bit of a challenge. In the combined candidate, Moderna will have to manage the safety profiles of its two components -- so that the resulting coronavirus/flu vaccine doesn't cause too many side effects.

How bad is this safety news for Moderna? Moderna says it's moving ahead to start its combined vaccine clinical trials this year. And Moderna also announced the launch of a combination vaccine program to target three respiratory viruses: flu, coronavirus, and respiratory syncytial virus (RSV). The safety results from the mRNA-1010 trial haven't changed the company's plans. So, right now, I'm not overly worried.

But there's a second reason why I'm not too worried. And that's because Moderna's future won't necessarily be tied to a coronavirus vaccine product. The company today has 31 programs in active development across a variety of indications.

While coronavirus products may be the revenue driver over the next few years, other products may take over farther down the road. Today, Moderna has potential blockbuster vaccine candidates for cytomegalovirus (CMV) and RSV in phase 3 trials. And the company is working on vaccines in other big areas such as HIV. All of this means Moderna has many possibilities for revenue drivers in the future.

Of course, the outcome of the combined vaccine program still is important. And it's an element to watch. But for me, it's not a determining factor to buy or sell Moderna stock. That's thanks to the depth of Moderna's pipeline, as I mentioned above. And over time, if even a handful of these pipeline programs succeed, Moderna and investors should succeed too.