Parents and physicians would welcome anything that protects children from ear infections. A recent report found some bad news - the flu shot has little effect on the frequency of ear infections. Previous studies found the flu shot reduced the rate of ear infections by a third.
This two year study of nearly 800 children, 6-24 months old, was the largest one so far looking at the possible protective effect of the flu vaccine. Half the children received the flu shot before the 1999-2000 and 2000-2001 flu seasons. The other half received a placebo shot. All the children were examined every two weeks during the flu season. They found no difference between the two groups in the incidence of ear infections.
So how do we reconcile the results of this study with the other three that did find a protective effect? According to Alejandro Hoberman, M.D., the lead researcher, the other studies had serious problems with methodology. These include small sample size, using only certain groups of children that may affect the results, lack of randomization of which children received the vaccine, and inadequate blinding of the investigators. (The investigators who evaluated the children knew which had received the vaccine and which didn't.)
"Our study was designed to overcome the methodologic limitations in the previous reports," said Dr. Hoberman. "We enrolled a large number of children, 6-24 months of age, who are at the highest risk for acute otitis media, instead of limiting enrollment to only those attending day care. Children were evaluated by validated observers every 2 weeks and at any time they had signs or symptoms of acute otitis media or upper respiratory infections."
Another factor that may explain the difference in results is the age of the children studied. This study had a larger proportion of younger children who are less likely to catch the flu.
This dilemma, when one study contradicts the results of others, exemplifies a problem common in medicine. Situations like this explain why many physicians are not quick to advocate "the latest and greatest" treatment. It takes many studies to clarify the results of the initial study. In this case, it may turn out that the flu vaccine does have some effect on the incidence of ear infections - but perhaps only in children of certain ages or who attend day care.
Family Practice News, 8/15/02, p. 30.
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