to the editor: In early March 2011, one-fourth of the attendees at a business meeting became ill with influenza-like symptoms. The meeting organizer sought immediate care from the hotel physician and subsequently the company medical leadership. Several persons were clinically diagnosed with influenza. Anecdotally, many of those who became ill had not received a seasonal influenza vaccination. After obtaining Institutional Review Board approval, we e-mailed a short questionnaire to the meeting participants to better understand the relationship between their symptoms and their vaccination patterns.

We collected information regarding the demographics of the participants; symptoms of influenza, the common cold, and allergies; and their vaccination status. A total of 122 persons responded to the questionnaire, representing 85 percent of the meeting attendees. The respondents represented 10 countries, with the majority from the United States and Germany. One-half of the participants were younger than 31 years, most were men, and most traveled more than three hours to attend the meeting. Forty-seven percent of the respondents had been vaccinated for influenza in the past 12 months.

For the purposes of analysis, influenza was defined as having more than two of the following symptoms: headache, fatigue, aches, or fever. Twelve participants met our definition of influenza and most of these (83 percent) had not received an influenza vaccination. The resulting odds ratio of 5.0 for vaccination was unlikely to be due to chance (95% confidence interval, 1.0 to 23.1).

A vaccination program for the seasonal and the novel influenza A (H1N1) virus is provided free-of-charge to all employees of The Dow Chemical Company and their spouses throughout U.S. locations and with similar programs worldwide. Despite messages from the company and local health agencies about the value of vaccination, there is still room for improvement in vaccination rates. This study of a cluster of influenza-related illness confirms that vaccination is protective. It also demonstrates the disruptive nature of influenza in business. Results of this study are being communicated company-wide to encourage all employees to be vaccinated during the current influenza season.