"Normally, older adults are generally more susceptible to pathogens like influenza, however, for the pandemic H1N1 strain this does not seem to be the case," said Dr. Scheuermann, who is also a member of the Cancer Immunobiology Center at UT Southwestern. "The antibody epitopes, which provide protection against disease, for the pandemic H1N1 strain are virtually all different from those present in recent seasonal strains, so young people have no built-in protective mechanisms. We speculate that older adults may have been exposed to viruses in their youth in which the epitopes are more similar."

At this point, he said, scientists must continue to be vigilant about tracking the pandemic H1N1 strain as it continues to evolve.

"H1N1 has not mutated in such a way as to make people sicker, but it could happen," Dr. Scheuermann said. "It is important that individuals follow the public health guidelines regarding vaccination as the H1N1 vaccine becomes more widely available."

The Centers for Disease Control and Prevention (CDC) recommendations include: pregnant women, individuals in contact with and caregivers of children younger than 6 months of age, health care and emergency medical services personnel, all individuals from 6 months through 24 years of age, and individuals aged 25-64 with health conditions associated with higher risk of medical complications from influenza.

Source: UT Southwestern Medical Center