CSL Ltd (ASX: CSL) shares have gone backwards over the past year.

Shares in the S&P/ASX 200 Index (ASX: XJO) biotech stock closed up 0.99% on Monday trading for $244.29.

Despite that welcome boost, shares remain down 10.61% in 12 months, underperforming the 5.56% gains posted by the ASX 200 over this same time.

Although it's worth noting that those losses will have been modestly mitigated by CSL's dividends. The stock trades on an unfranked trailing dividend yield of 1.7%.

While CSL shares have been under selling pressure since last August, United States President Donald Trump's indication that imported medicines may get hit with tariffs hasn't done shareholders any favours.

But, according to Catapult Wealth's Dylan Evans, the market's reaction to those as-yet undeclared tariffs could make now an opportune time to buy stock in CSL (courtesy of The Bull).

Why CSL shares are a buy

"The share price of this biotechnology giant has been trending down since mid-2024," said Evans, who has a buy recommendation on CSL shares.

Commenting on Trump's tariff warnings, he said, "Threats from the Trump Administration to extend tariffs to imported pharmaceuticals would possibly have a negative impact on CSL, given it generates around half its revenue in the US."

But that isn't dissuading him from buying the biotech stock.

"Despite these risks, we believe CSL represents good value," Evans said. "It remains a high quality company, delivering double digit earnings growth. It looks cheap compared to global peers."

And with the market having already discounted CSL amid expectations of those tariffs, Evans noted, "The impact of US tariffs is factored into the share price, so, in our view, there's upside potential if they are withdrawn, or lower than anticipated."

Also bullish on the ASX 200 biotech stock

Tyndall Asset Management's Tim Johnston also has a bullish outlook for CSL shares (courtesy of The Australian Financial Review).

Atop headwinds from potential US tariffs on pharmaceuticals, CSL has also come under pressure following the confirmation of Robert F Kennedy junior, a vaccine sceptic, as US health and human services secretary.

At the company's half-year results (H1 FY 2025), CSL already reported a 9% decline in revenue at Seqirus, its vaccine division. That was driven by low immunisation rates, especially in the US.

But Johnston doesn't believe these headwinds will persist for CSL shares.

"Common sense will prevail, science will win out," he said of the US vaccination rates.

"And CSL at 21 times earnings for a stock that's probably going to deliver low double-digit earnings growth for the foreseeable future is as cheap as I have seen it," Johnston said.