Jefferies reduced its price target to $76 from $86 and reaffirmed its hold rating for CVS Health shares, telling its clients to stay on the sidelines until the uncertainty passes.
Despite the report, CVS' share prices were up 1 percent Tuesday morning.
CVS reported better-than-expected third-quarter earnings Monday morning. The company also revealed a next-day and same-day prescription drug delivery service in select markets. Its stock declined 3.5 percent Monday, closing at $66.80 after the announcements.
"Based on recent trading patterns (including yday's reaction to CVS's introduction of same-day/next-day Rx delivery that some viewed as a defensive move against a supposed Amazon's entry into Rx), it is evident that overhangs related to speculation of an Aetna purchase and Amazon's supposed pharmacy plans are the more relevant drivers of [near term] stock performance," analyst Brian Tanquilut wrote Tuesday.
"Since it is difficult to refute either overhang, we believe investors will continue to put a discount on CVS shares until some clarity emerges on these issues."
The company's shares have underperformed the market this year due to concerns Amazon is considering selling prescription drugs online. CVS Health stock is down 15 percent in 2017 through Monday, compared with the S&P 500's 16 percent return
Reports last month said CVS Health is in talks to buy health insurance company Aetna in potential health-care megadeal. Some analysts have speculated CVS Health may be considering the acquisition of Aetna to protect itself from potential Amazon disruption.
"They needed to defend the business from encroachment by Amazon," RBC Capital Markets analyst George Hill told CNBC on Oct. 26. "Amazon's ability to impact the business over the near to mid term is low, but the ability to impact the stock is high."
CVS Health did not immediately respond to a request for comment.