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Up 73% year to date, this stock in my SIPP is suddenly on fire!

After three years of wealth-destroying losses, this S&P 500 stock’s suddenly roared back into life in our writer’s SIPP. What’s going on?

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Every time I click on my phone’s Self-Invested Personal Pension (SIPP) app, a particular stock stands out like a sore, throbbing-red thumb.

That holding’s Moderna (NASDAQ:MRNA), the mRNA vaccine pioneer whose share price fell 45% in 2023, 58% in 2024, then 29% last year.

XXX

In 2026 however, it’s like a switch has been flipped. Year to date, Moderna’s up 73%, making it the second-best-performing S&P 500 stock so far this year. Only SanDisk, which was also the index’s best-performing stock in 2025, is doing better.

So what’s going on with Moderna? And more to the point, might the stock be worth considering today?

Slumping sales

If Moderna sounds like a blast from the past, it’s due to its indelible associations with the global pandemic. Or, more specifically, its mRNA vaccine (Spikevax) that was rapidly rolled out to millions of people worldwide.

This single product created an eye-popping $19.3bn in revenue and $8.4bn net profit in 2022. Since then though, sales have collapsed, with revenue of just $1.9bn generated last year (and a financial loss).

Naturally, sales were always going to decline significantly once the pandemic subsided and normality returned. However, they’ve fallen far faster than anticipated, while President Trump’s selection of vaccine sceptic Robert F Kennedy as health secretary hasn’t helped.

Millions more Americans are now extremely wary of vaccines, especially experimental mRNA ones. Research funding has also been pulled, leaving investors very bearish on vaccine makers.

This political development/risk was something I didn’t anticipate. But with hindsight, I should have done, as Trump had a history of vaccine scepticism predating his re-election campaign.

Why’s the stock spiking higher?

That said, I didn’t invest in Moderna just for its Covid vaccine. I did so because I thought there was a strong chance that its cutting-edge mRNA technology could be extended to other diseases, including cancer.

Developments here have put a rocket underneath the stock recently. Because Moderna and partner Merck have announced that their experimental personalised vaccine cuts the risk of death or recurrence of melanoma by 49% five years after the start of treatment.

This was consistent with data released in 2023. And it obviously bodes well for the forthcoming phase 3 data, as well as Moderna’s other eight mid- and late-stage studies in bladder, kidney and lung cancer.

Cases of melanoma, which is the most serious form of skin cancer, are rising worldwide. Analysts at Jefferies reckon this cancer vaccine has the potential to generate multi-billion-dollar peak sales in melanoma alone.

An mRNA flu vaccine should also be approved this year.

A high-risk stock

As exciting as this sounds, it’s important to not get carried away. Late-stage melanoma data isn’t expected till the end of 2026 at the earliest, and successful phase 3 clinical trials are never guranteed.

In the meantime, Moderna’s investing heavily in its large pipeline and doesn’t expect to reach cash flow breakeven till 2028.

Another thing worth mentioning is that before this news, the stock was heavily shorted, so we could be witnessing an unsustainable short squeeze. Investors should therefore be careful chasing this stock higher.

Moderna’s potential is significant, but so are the risks, and it might take years for its promise to translate into actual earnings. I’m not selling my shares, but neither am I buying more.

Ben McPoland has positions in Moderna. The Motley Fool UK has recommended Moderna. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

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