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Am Fam Physician. 2004;70(7):1392

Influenza is linked to as many as 37,000 deaths annually in the United States, especially among the elderly. It is also associated with elevated rates of hospitalization in children. Recently, there have been recommendations to increase the use of influenza vaccinations among children younger than two years. Ruben reviewed the data on the safety and efficacy of inactivated (“killed-virus”) influenza vaccines in children.

The author reviewed 22 studies of influenza vaccine use in children, published since 1970, for a pooled population of more than 4,600 children. Studies from the 1970s showed increased systemic reaction rates with the use of whole-virus vaccines compared with the split-virus versions. Protective antibody titers (greater than a fourfold increase) were achieved more readily with vaccines against influenza A strains than against influenza B strains. Subsequent studies from the 1980s to the present also indicated that systemic reactions were more common with whole-virus vaccines, although this was not a universal finding. Studies that used two doses of vaccine demonstrated the highest rates of protective antibody titer formation in healthy children.

Efficacy studies of inf luenza vaccine in healthy children and those with increased risks for complications (such as those with asthma) showed that vaccination against influenza A strains conferred protection 31 to 91 percent of the time, with most studies noting protection rates above 65 percent. Efficacy against inf luenza B was somewhat less, varying from 44 to 45 percent.

Two separate studies showed reductions in rates of acute otitis media after influenza vaccination, but one large study found no significant reduction. Population-based data also were reviewed from Japan, where there was a national policy to vaccinate all school-age children for inf luenza in the 1970s (the policy was reversed in 1994). During this 20-year period of widespread immunization, annual mortality related to pneumonia and influenza decreased by 10,000 to 12,000 deaths, and annual all-cause mortality declined by 37,000 to 49,000 deaths. Rates rebounded when vaccination was suspended.

The author also reviewed several cost-effectiveness studies, each of which concluded that influenza vaccination would likely produce an overall cost savings. However, the American Academy of Pediatrics issued a report noting that providing two doses of vaccine during the brief time each fall when vaccination is indicated presents substantial logistic challenges.

The author concludes that extensive studies of influenza vaccine in children indicate that it is safe and effective. The review recommends the use of two vaccine doses to provide maximal protection.

editor’s note: I must confess a certain reluctance to go along with the rising chorus of public and health authority calls for universal influenza vaccination in young children. Vaccine safety is well established, and some efficacy in reducing infection rates is clear. However, the logistic concerns of adding another one or two properly timed immunizations each year for children younger than two years are not trivial, and the overall benefit derived from this substantial investment does not seem as readily apparent as that linked with other widely used preventive health measures. I wonder if the present enthusiasm may wane over time for this recommendation. I think the policy reversal in Japan after some years of widespread use speaks volumes.—B.Z.

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