Flu vaccine may not be effective at staving off pneumonia among the very elderly, according to a new report.

Conventional wisdom says that if a flu vaccine does not prevent the flu, it at least hinders the development of some of the complications that arise from the flu, including pneumonia, according to researchers from the Group Health Center for Health Studies in Seattle. Their study found otherwise. Vaccinated seniors between the ages of 65 and 94 developed pneumonia at similar rates to seniors who were not vaccinated over the course of three flu seasons, the study found.

While influenza vaccines may not be as effective among the elderly as previously thought, it’s still a good idea to get the inoculation, researchers say. Having many seniors vaccinated, especially those living together in a community, can build a collective resistance to the virus, according to health experts. Each year, more than 36,000 Americans die from influenza, 90% of whom are elderly, according to the Centers for Disease Control and Prevention.