Flu Vaccine Doesn't Work For All Children

By Margarita Nahapetyan

Flu vaccine can triple the risk of hospitalization for children, and especially the ones with asthma, when compared with kids who have not received the shot, according to a new study by the U.S. scientists at the Mayo Clinic in Rochester, Minnesota.

The main goal of a new research was to evaluate the effectiveness of the flu vaccine (trivalent inactivated flu vaccine, or TIV) in children, said Dr. Avni Joshi, MD, Fellow at Allergy, Immunology and Infectious Diseases department in Mayo Clinic. Dr. Joshi said that kids with asthma were of particular concern.

The Mayo Clinic study analyzed eight consecutive flu seasons in order to determine whether the flu vaccination was effective in reducing the number of hospitalizations that all children, and especially the ones with asthma, faced over this period of time. The investigators involved more than 250 children with the ages between six months and eighteen years, each of whom had laboratory-confirmed influenza between 1996 and 2006. The experts determined which kid had and which had not received the flu shot, as well as the status of their asthma and who did and did not require to be taken to hospital. Records were examined for each child with influenza-related condition for flu vaccination given before the illness and stay at the hospital during that illness.

They results revealed that children who had been administered the flu vaccine were three times more likely to be hospitalized, compared to the kids who had not received the shot. In asthmatic children, there was a significantly higher risk of hospitalization in patients who received the TIV, when compared to those who did not (p= 0.006). But no other measured factors, such as insurance plans or severity of the condition, appeared to have any effect on the risk of hospitalization.

There is no reason to believe that the flu vaccine necessarily was the cause of hospitalizations, Dr. Joshi stressed out. This could simply mean that the vaccination did not appear to be effective in preventing hospital stays. "The flu shot may be safer in terms of triggering a wheezing episode, but we do not know how effective it is," the expert said and added that much more studies and investigation is needed on this matter in order to determine the effectiveness of different kinds of vaccines. Dr. Joshi hopes that the scientists would come up with something that will have higher efficacy not only in preventing influenza illness, but also hospitalizations. Vaccination should be universal, she said, but the experts may need to find more effective vaccines, Joshi added. "This is a good vaccine. We could have better," she concluded.

The CDC and the American Academy of Pediatrics have recommended to vaccinate all children between the ages of 6 months and 18 years every year. The National Asthma Education and Prevention Program (3rd revision) also recommends annual influenza vaccination of children with asthma older than 6 months.

The new study was presented on May 19, 2009, at the 105th International Conference of the American Thoracic Society in San Diego.