Flu season is nothing to sneeze at for you and your employees. Each year the flu blues cost businesses billions of dollars. Though experts say much of that cost and personal hardship could be avoided if workers got flu shots, motivating them to do so is a major challenge.

Giving them a simple nudge may be the answer, according to a new study.

Each year on average, 200,000 Americans are hospitalized with seasonal flu, costing businesses more than $10 billion in hospital and outpatient costs and an additional $76.7 million from absenteeism and other indirect expenses, according to the Centers for Disease Control and Prevention.

Employers across the nation pull out the stops to encourage, cajole, assist, incentivize and beg employees to get their flu shots. Yet only about 20 percent of workers will receive one, even when it is offered at no cost.

Simple messaging that prompts employees to "make a plan" by writing down the specific date and time when they intend to complete a health activity can significantly increase the likelihood of follow-through, according to new research conducted by academics at the University of Pennsylvania, Stanford, Harvard and Yale along with Evive Health, a health-engagement technology company.

In a controlled study of 3,272 employees, a simple planning prompt message increased employee flu shot participation by 7.9 percent.

"Employers have a vested interest in reducing sick days at the worksite, and flu shots are an important preventive tool to achieve that," said Peter Saravis, CEO of Evive. "Fortunately, breakthrough studies in behavioral science are helping us understand new ways to motivate employees to participate in healthy behaviors such as getting a flu shot.

"Our research found that prompting people to simply write down the specific date and time for when they planned to get a flu shot was a highly effective and zero-cost method for increasing flu shot compliance. We believe that similar prompts can be used to increase employee engagement in many other healthy behaviors that people often intend to follow through on but end up overlooking due to competing demands on their time."