A nasal-spray version of the flu vaccine protects some young children better than flu shots, according to a study partially funded by the spray's manufacturer.

Since children get the flu twice as often as adults, and babies and the elderly are at highest risk of dying from complications of influenza, the study was designed to provide information on a vulnerable age group.

A nasal-spray flu shot may lead to fewer tears.
(CBC)

Robert Belshe, of the Saint Louis University School of Medicine in Missouri, and colleagues compared the two types of vaccines on 8,400 preschoolers in 16 countries during the 2004-2005 flu season.

In Thursday's New England Journal of Medicine, the team reported that 8.6 per cent of children getting the traditional shot got the flu, compared with 3.9 per cent among those given the spray.

But for infants between six to 12 months of age or older children who wheeze, the shots seemed safer, the team found. Among children under the age of one, there were slightly more hospitalizations and wheezing in the nasal spray group.

The nasal spray, called FluMist, is squirted up the nose. It is not approved for use in children under five in the U.S., although last month, regulators approved it for healthy people aged five to 49. Health Canada has not approved FluMist.

Protection in the nose

Flu shots use killed viruses and are injected into the muscle, while FluMist uses live, weakened viruses. It's thought that live, weakened vaccines may offer better protection for children who have never had the flu and have few antibodies to fight it.

"The big difference is the induction of antibodies in the nose, which is important because this is where the flu virus usually enters the body. The nasal spray flu vaccine appears to induce a more complete immune response," Belshe said.

Traditional flu shots stimulate antibodies in the blood but not in the nose.

There were also fewer ear infections linked to the flu in children who received FluMist compared with those who received the shot, the researchers found. The complications can occur when the illness damages mucous membranes in the sinuses, ears and windpipe.

The nasal-spray vaccine also helped to prevent the flu when the viral strains in the vaccine did not match the circulating strain.

Safety review

In a commentary accompanying the study, Nancy Cox and Dr. Carolyn Buxton Bridges of the U.S. Centers for Disease control said the live, weakened vaccine may be better for some children, since the youngsters may prefer receiving a spray to a jab, and it may offer more protection than traditional shots.

Although the results are encouraging, safety data for the spray needs to be reviewed carefully by regulators before they consider approving it for use in children under five, the two said.

Since the study did not include unvaccinated children as controls, it is impossible to tell whether the vaccines offer more protection than no vaccine — important information for comparing the performance of the vaccines in relation to safety and cost, the commentary noted.

Between 500 and 1,500 Canadians — mostly the elderly and young children — die annually from flu complications.