Influenza vaccination
reduces pneumonia deaths

NEW YORK — Patients hospitalized for community-acquired pneumonia are about 33 percent less likely to die if they are up to date with their influenza vaccinations, even if the effectiveness of the vaccine is suboptimal, results of a four-year study suggest.

Despite its known benefits, many people who have the greatest risk are not vaccinated, Dr. David N. Fisman and associates note in the Archives of Internal Medicine. One reason may be the fact that the vaccine does not prevent all cases of influenza, although it is likely to make the illness less severe.

"Information on protection against death, even in the absence of prevention of infection, could form the basis of an extremely effective public health message promoting vaccination," the authors propose.

To prove their point, Fisman, currently at the Research Institute of the Hospital for Sick Children in Toronto, and colleagues collected data for 38,000 consecutive individuals hospitalized with community-acquired pneumonia at 34 institutions during four influenza seasons starting in November 1999.

The investigators classified the patient’s risk using demographic information, the presence of other illnesses, and various clinical factors, to calculate Pneumonia Outcome Research Team scores. Complete records for 17,393 - about half of the patients – were available for analysis.

The overall mortality rate was seven percent. The 1,590 currently vaccinated patients were less likely to die during hospitalization than the 6,661 who had never received an influenza vaccine, even though the vaccinated patients were older and had higher pneumonia scores.

Vaccinated patients were also more likely to survive than 9142 subjects whose vaccination status was unknown.

"No statistical evidence was found to suggest that influenza vaccination was less effective in preventing death in individuals 65 years or older," the investigators report.