It’s just too soon to say for sure but officials at the US Centers for Disease Control and Prevention (CDC) have evidence that suggests people 60 years old and older may have a natural immunity to the new swine flu virus sweeping the globe that younger individuals do not have.  This suspected immunity comes from long-ago exposure to a swine flu virus that is similar to the new strain now in circulation.

In 1957, the world faced the Asian flu pandemic, which produced many of the viral strains that now cause common, seasonal flu outbreaks every year.  Before 1957, common seasonal flu outbreaks were caused by viruses that, genetically, resemble more closely the current swine flu strain.  It’s the exposure to the pre-1957 viral strains that are thought to be protecting older people today.

Scientists at the CDC analyzed blood samples, taken before the current epidemic began, from individuals in the United States and Europe, looking for antibodies that would indicate immune protection against the current strain.  All samples were taken from people who were healthy, with no flu-like symptoms, at the time their blood was drawn.

Although the number of overall samples is small, one out of every three samples taken from individuals 60 and older indicates significant protection.  Samples taken from younger individuals indicate protection in only one of ten samples.

The findings from this analysis may help explain the high rate of younger individuals getting the current swine flu.  As a rule, older patients are more likely to develop symptoms and have more severe symptoms than younger patients but the current flu seems to be hitting younger adults harder than the elderly.

As many as 100,000 Americans are thought to have been infected with the current swine flu strain although swine flu has been confirmed in just over 5,700 cases.  Of them, 40% of those requiring hospitalization are between 18 and 50 years of age.  Overall, this age group is thought to constitute about 60% of all infected individuals, whether or not hospitalization has been required.  Nine deaths from swine flu have been confirmed in the US thus far but the CDC suggests the number may actually be 10 deaths.

Because the number of samples analyzed is small and the lab tests have not yet been verified, officials at the CDC are still advising older people to take the same precautions as younger people, including getting vaccinated once an effective vaccine has been developed.  Current speculation is that older individuals may need just one vaccination while younger individuals may need a booster shot or to for maximum protection.