What happened

Shares of CVS Health Corporation (NYSE:CVS) were down 6.7% as of 3:23 p.m. EDT Thursday. Two factors appeared to be behind the pharmacy services stock's decline.

On Wednesday afternoon, CVS Health announced that it had entered into an agreement with the U.S. Department of Justice (DOJ) that allows it to move forward with its planned acquisition of Aetna (NYSE:AET). Some investors and analysts have expressed reservations about the deal.

Pharmacist with customer holding CVS basket in CVS Health pharmacy.

Image source: CVS Health.

Also, Walgreens Boots Alliance (NASDAQ:WBA) missed Wall Street revenue expectations with its fiscal Q4 financial results announced before the market opened Thursday. The company, which is CVS Health's largest rival, reported that its sales increased 10.9% to $33.4 billion. Analysts, however, expected Walgreens to post Q4 revenue of $33.78 billion.

So what

The more important news for CVS Health was the DOJ agreement that allows the company to proceed with plans to buy Aetna. This is a big bet that CVS Health CEO Larry Merlo is leading his company into -- a $69 billion bet.

Because of its intention to acquire Aetna, CVS Health has already suspended hikes to its dividend. That's usually a sure-fire way to make investors unhappy. The company is also taking on additional debt to finance the transaction on top of assuming Aetna's $8 billion debt.

There are several potential positives associated with the Aetna deal, though. CVS Health will be the only entity with retail pharmacy, pharmacy benefits manager (PBM), and health insurance businesses. The company thinks that this integration will enable it to improve healthcare for customers and more effectively control costs.

As for Walgreens' revenue miss, the most important thing to note was that same-store retail sales fell 1.9% year over year. Walgreens particularly noted weakness in consumables, general merchandise, and personal care products.

CVS Health posted its own year-over-year decline in same-store front-store sales in the second quarter, due largely to the impact of the timing of Easter. Walgreens' lagging retail sales could be a hint that CVS Health could have another anemic quarter of front-store sales when it announces Q3 results next month. 

Now what

The main thing for investors to watch for with CVS Health concerning the Aetna acquisition is how quickly the company lines up regulatory approvals in the remaining states that haven't already given a thumbs-up to the deal. CVS Health expects, though, that the transaction will close relatively quickly.

CVS Health is scheduled to provide its Q3 update on Nov. 6. The company has already lowered earnings expectations for the quarter. Over the long run, investors need to keep their eyes on how effectively CVS Health leverages its integration with Aetna. That will matter a lot more than how well the company performs in one quarter.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.