Nasal Flu Vaccine More Effective in Children (I)

by BETH M. WICKLUND, M.D.

Young children and their parents may soon have less of a reason to cry when going to the doctor.

A nasal spray vaccine for the flu virus has been shown to be more effective in children than the standard intramuscular needle injection currently being used.

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New Mammogram Guidelines | Ask Dr. TimIn a study of nearly 8,000 children released today in the New England Journal of Medicine, children younger than 5 years old who received the nasal vaccine developed 55 percent fewer cases of the flu than those who received the injected vaccine.

"This vaccine will eventually lead to an easier process of vaccination and will substantially change the way pediatricians vaccinate children against the flu," said Dr. Robert Belshe, lead author of the study and director of the Center for Vaccine Development at Saint Louis University Health Sciences Center.

Not only did the nasal spray beat out the injectable vaccine against the strains of influenza actually contained in the vaccines, but it also prevented more infections caused by strains that were genetically drifted, or different, from the vaccine strains.


"It's as though you get a double-bang effect," said Dr. William Schaffner, chair of the department of preventive medicine at the Vanderbilt Medical School in Nashville, Tenn.

"You get protection against the kind of influenza that is in the vaccine, as well as the kind that sometimes occurs out in the community and is a little bit different," Schaffner said.

Should all children now start to receive the nasal vaccine? There are precautions. Children who are 6 months to 1 year of age were almost twice as likely to develop wheezing and other illnesses within six weeks of their immunization if they received the nasal vaccine rather than the injected one.

In addition, all children with a history of wheezing or asthma -- even older children -- were slightly more likely to be hospitalized if they were given the nasal vaccine.

The reason for the rise in other illnesses is unclear, but it is concerning enough that Belshe says, "The nasal spray vaccine should become the vaccine of choice for children over 1 year of age without a history of wheezing [or asthma]. It is easier to use and has greater efficacy."

Flu vaccines are still very important for infants between 6 months and 1 year, and the injected vaccine should continue to be used.

Dr. Kathleen Neuzil, chair of the Pandemic Influenza Task Force of the Infectious Disease Society of America, said, "If the nasal vaccine causes some side effects, then we need to weigh the risks and benefits in each patient."

Future studies may investigate a combination of the injected and nasal vaccines in an effort to balance efficacy and safety in children younger than 1 year old.

The nasal vaccine contains virus that is still alive but disabled, so it doesn't cause the flu itself. In children, the live virus multiplies in the body and causes a stronger immune response than the injectable vaccine, which contains only inactivated virus particles.

This form of the vaccine is not as effective in adults, whose more mature immune systems do not allow the virus to replicate as much.