Older Americans Have Some Immunity to Swine Flu, but It’s Not Absolute

When they do contract a severe case of flu, they face greater risk
By: Katharine Greider | Source: AARP Bulletin Today | November 11, 2009

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One of the most surprising characteristics of the pandemic H1N1 flu virus galloping across the country this fall is the way it tends to spare older people, striking hardest among the young. More than half of U.S. patients hospitalized with the so-called swine flu have been under the age of 25. Small studies have found that people over age 60 have some antibodies to the bug.

But, whatever immunity to H1N1 older people may enjoy, it’s definitely not foolproof. A recent report on H1N1 cases in California injects a note of caution about the risk profile of people age 50-plus. While they were less likely to get a severe case of H1N1 flu, those who did were more likely than younger people to lose that battle and die.

Published Nov. 4 in the Journal of the American Medical Association, the study examined the first 1,088 H1N1 cases in California that required hospitalization or resulted in death, the bulk of them occurring between last spring and early summer. The median age of these sick patients was only 27, with about a third under 18. While those 50 and older were underrepresented in the group, their fatality rate was 18 to 20 percent, compared with only 11 percent overall.

To a large extent, this finding reflects not age alone, but also the fact that older people tend to have more health issues that make it difficult to fight off an infectious attack on the respiratory system. In fact, 88 percent of study cases among people 50 and older also involved some preexisting health condition. These included traditional risk factors for complications such as flu-like asthma, heart disease and diabetes, plus additional risk factors recorded in the study, including high blood pressure and high cholesterol, according to Janice K. Louie, M.D., the study’s lead author and chief of the Influenza and Respiratory Syndromes Section of the California Department of Public Health.

Still, the advice of federal health officials to focus initial H1N1 vaccination efforts on younger people makes sense, says Louie, not only because they’re more at risk, but also “because they are often the spreaders.” Older people frequently contract this virus from young children who don’t have as much immunity and, she says, “who have high levels of the virus when they get sick.”

Other important information emerging from this study of severe cases in the first 16 weeks of the H1N1 pandemic:

• The most common symptoms were fever, coughing and shortness of breath.

• The time of symptom onset to hospitalization was, on average, two days.

• Rapid on-site flu tests produced false negatives in a third of cases.

• One-fifth of the patients never received the antiviral medicine that can alleviate symptoms and even save lives.

The takeaway message, says Louie, is that the new flu isn’t always as mild as it’s often made out to be. People who develop the above symptoms should seek medical attention promptly, and doctors shouldn’t wait for test results to treat hospitalized patients with antivirals.

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Katharine Greider lives in New York and writes about health and medicine.

Comment

Those of us 60 and older have apparently been exposed to a similar virus from the 1970s, so we have some immunity.