CDC suggests that older adults may have pre-existing antibodies to combat H1N1

ATLANTA A study published last week in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report determined that older adults might have some pre-existing antibodies against the novel H1N1 virus, which would explain why this new virus is more prominent among younger, healthier populations.

Those antibodies may have come from past flu shots.

“The presence of preexisting antibody may be due to previous exposure through infection or vaccination to an Influenza A (H1N1) virus that more closely related to this novel H1N1 virus than the contemporary seasonal H1N1 strains that we had,” stated Anne Schuchat, director of immunizations and respiratory diseases. "We don't know yet what that will mean in terms of actual immunity or clinical protection. It's interesting that the laboratory findings we're reporting seem to correlate with the epidemiologic data that we have so far that suggests most of the illnesses we're seeing have occurred in younger people and have spared the elderly, who are at great risk for seasonal influenza.”

Of the cases reported to the CDC that have undergone laboratory testing, 64% are occurring in people between 5 and 24 years of age. Conversely, just about 1% of cases are in people over 65. “So the vast majority are in younger persons, and the biggest proportion of those are people in the 5- to 24-year-old age group,” Schuchat said.

The results presented in the study found that the current seasonal influenza vaccine provides little or no immune benefit against the novel H1N1 flu virus. Further, the laboratory results, while interesting, do not necessarily indicate that seniors may have some level of immunity to the H1N1 virus currently circulating, Schuchat said.