Pfizer's stock (PFE) surged more than 4% Monday morning after reports that activist investor Starboard Value had taken a $1 billion stake in the pharma giant.

The investor wants to help turn around the company's lackluster performance in recent years, according to reports late Sunday evening. Pfizer declined to comment.

Pfizer's stock has been stagnant despite its COVID revenue windfall. Investors have instead been focused on an underwhelming portfolio, several blockbusters facing patent expiry in the next few years, and reduced revenues since the end of the pandemic.

"The stock has been held in check over the past year, trading between the mid $20s to low $30s and not doing much outside of a pretty tight range. Longer-term, this is one of the most disappointing names in large-cap healthcare with an uninspiring chart over almost any duration dating back to the 1990s," wrote Mizuho's healthcare expert Jared Holz in a note to clients Monday.

CEO Albert Bourla has attempted to put a spotlight on the company's aggressive strategy, from betting his entire pension on the company's stock earlier this year to the $43 billion Seagen deal and launching a dozen new products in the second half of 2023.

No COVID reward

During the pandemic, when other COVID players saw their stocks spike, Pfizer's barely budged. Despite being the lead vaccine in the US and in some countries around the world, Pfizer's stock was not similarly rewarded.

Bourla remained optimistic then, telling Yahoo Finance, "We do think our stock is undervalued, but we do not worry that investors cannot see it."

By 2023, Bourla sounded weary. "Although I'm not happy, all we can do is to execute on our strategy so that investors will see that this is a good growth opportunity," Bourla told Yahoo Finance.

In 2021, then CFO Frank D'Amelio, who has been reportedly tapped by Starboard as a consultant, told Yahoo Finance, "There's a lot more value to unlock. Investors will start to warm up more to the story."

That hasn't happened. Despite meeting its target of 6% growth in the top line over the last few years — even after steep COVID declines — investors haven't warmed up.

The stock peaked at $60 per share in December 2021 when the company filed jointly with partner BioNTech (BNTX) for FDA approval of its COVID vaccine in teenagers — a year after adults had access.

Aggressive M&A

Bourla has struggled to convince Wall Street of Pfizer's value since taking the helm in 2019. At the time, Pfizer was pivoting away from its consumer healthcare business with a GSK (GSK) joint venture and had spun off its generics business Upjohn. The company was just starting to contend with the idea that it had products facing a patent cliff by the end of the coming decade.