I currently have 41 investments in my portfolio, comprising mainly FTSE 100 dividend stocks and growth shares. Many are performing well, some splendidly.

Inevitably though, I’ve got half a dozen that are stinking the place out. Two are really irritating me. Should I get rid of them?

The Nasdaq one

The first one’s my biggest loser: Moderna (NASDAQ: MRNA). The stock’s down 77% over the past year!

During the pandemic, Moderna’s mRNA Covid vaccine was administered into hundreds of millions of bodies. Those hundreds of millions of jabs quickly translated into many billions of dollars of profit.

Of course, that was never going to last, and when I invested in 2023 the share price was already down around 70% from its pandemic peak. Unfortunately, it’s headed even lower since, as declining Covid sales have not been offset by new approvals.

So what possessed me to invest? Well, Moderna’s mRNA technology works a bit like software for the body. As Moderna CEO Stéphane Bancel puts it: “With mRNA, it’s four letters [A, T, C, G], like zeros and ones with software. You code everything.”

In theory, this digital-like platform model gives Moderna huge scalability advantages. It can be adapted for a potentially wide range of uses, from flu and HIV to personalised cancer vaccines.

Management’s targeting up to 10 new product approvals over the next couple of years. Its second mRNA vaccine, for respiratory syncytial virus (RSV), is already on the market.

Meanwhile, it’s vaccine for skin cancer has shown great promise. In a phase 2 study, it demonstrated a 49% reduction in recurrence or death. Moderna has various cancer vaccines in the clinic, including for lung and bladder cancer. They could be game-changers, for both patients and Moderna.

However, while these vaccines have blockbuster potential, there’s no guarantee they’ll get approved by regulators. Moreover, the Trump administration’s ambivalent view on vaccines, to put it mildly, is a challenge. Funding for a potential bird flu vaccine was recently pulled.

Moderna expects to end 2025 with $6bn in cash. And analysts see revenue growth resuming in 2026, rising 16% to $2.4bn. Then up another 25% to $3bn in 2027. No profits though.

I’m hanging on to my shares, but it’s a long way back.

The second struggling stock is JD Sports Fashion (LSE: JD). While the share price has jumped 22% in the past week, I’m still down around 17% after investing last year.

JD’s been hurt by a slowdown in consumer spending. We don’t know when that will improve, and it could even get worse. This is the key risk here.

Yet the company’s still opening stores worldwide, and grew its sales 10% to £11.5bn during the year to 1 February. The shares have been rising because investors are backing a potential return to growth at key partner Nike.

JD shareholders will hope so, as Nike’s products account for around 45% of total sales. And the two share prices tend to move in lockstep.

However, the sportswear retailer also sells trend-driven brands such as On and Hoka. While Moderna’s more of a speculative moonshot, I reckon JD Sports deserves further attention from investors.

The stock’s trading at just 7 times forward earnings, which still appears far too cheap to me.