Last week, the merger between health care giants CVS and Aetna overcame its first hurdle: the US Justice Department gave permission for the $69 billion deal to proceed. Now leaders at both organizations face the challenge of blending the two companies.

A change of this magnitude undoubtedly stokes fear among employees and raises many internal questions. Research shows that employees going through a merger look for trust, stability, confidence and empathy in their leaders. So what should CVS and Aetna executives due to make this merger as seamless as possible? We have some tips.

Think about culture.

Too often leaders ignore company culture, both before the deal is signed and throughout the integration. We know that a single culture is extremely difficult to shift. Combining the cultures of two organizations is even more challenging.

CVS and Aetna executives should first assess their current cultures. (We suggest using the PRIDE method.) Assessments would create detailed pictures of CVS and Aetna’s cultures to fuel a post-merger integration plan that focuses attention on the most critical success factor – the people.

Communication is key.

During any big change, it’s natural to want to delay messaging until there is perfect alignment and all facts are in order. But if CVS and Aetna don’t start communicating quickly, they run the risk of rumors and falsehoods spreading amongst employees. That’s why we recommend getting leadership aligned on a message cascading it through their organizations as soon as possible. Remember: during uncertain times, employees crave trust, stability, confidence and empathy in their leaders. A single, solid message is what they need.

Accept resistance.

Not every employee is cheering as CVS and Aetna merge. Most change initiatives have hecklers; how do you confront them? You don’t. Leadership should focus their energy on their “sweet spot” – those who are open to the idea and who can influence the outcome. Leaders should educate and engage them as project advocates. These grass-roots change agents can create momentum toward a successful merger.

As CVS and Aetna travel toward happily merged bliss, there will be bumps along the way. If leaders consider culture, communicate quickly and create agency within the workforce, they will pave the way to success.