Pfizer’s (PFE) stock has fallen ill since the COVID-19 pandemic waned, and it is still experiencing some aftereffects. The pharmaceutical giant, best known for its COVID-19 products (Paxlovid and Comirnaty), Eliquis, and Prevnar, a pneumococcal vaccine, has been dealing with difficult year-over-year comps due to a withering COVID-19 portfolio. Moreover, many of Pfizer’s products, like Eliquis (2027 to 2029) and Ibrance (2027), face “patent cliffs.” That means their time for market exclusivity is running out. With generic drugs entering the market, revenue generated by these branded drugs drops substantially. Don't Miss Our End of Quarter Offers: Discover the latest stocks recommended by top Wall Street analysts, all in one place with Analyst Top Stocks. Make smarter investments with weekly expert stock picks from the Smart Investor Newsletter. To make matters worse, Pfizer and many other biopharma companies are adjusting to a shakeup at the Food and Drug Administration (FDA), which could have overreaching impacts on drug development and regulation. Pfizer (PFE) Despite its apparently cheap valuation and a healthy dividend yield of 6.7%, these factors make Pfizer stock a difficult Hold in the months ahead, so I am neutral. Regulatory Headwinds and Investigations Last week, The Wall Street Journal reported that Pfizer is being investigated for allegedly delaying positive results from its COVID-19 vaccine trial before the 2020 election. The news could potentially throw Pfizer into the firing line of various U.S. authorities, especially with President Donald Trump so gung-ho for justice relating to the 2020 election aftermath. Trump’s “Operation Warp Speed” is credited for accelerating the development of COVID-19 vaccines when tens of thousands of people were dying. Reportedly, a former Pfizer scientist tipped federal prosecutors shortly after President Trump lost his re-election bid in November 2020. The allegations could have legal, reputational, financial, and stock price implications if they prove true. If Pfizer withheld material information from regulators or investors for political or market timing, it may face action from the Securities and Exchange Commission (SEC) or the Department of Justice (DOJ). Although politically motivated announcement delays will likely be difficult to prove, just the report alone could damage public trust. In the worst case, if investigations expand, it could sour institutional trust and weigh on Pfizer’s stock performance. As if the stock could take any more battering over the past few years.