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Flu Shots or Intranasal Flu Vaccine for Children?

The cold-adapted live attenuated intranasal vaccine is more effective than the intramuscular flu vaccine.

The current recommendation for controlling influenza is to vaccinate all children aged 6 to 59 months with intramuscular (IM) trivalent inactivated influenza vaccine. However, this adds another shot to the immunization schedule, the vaccine’s efficacy is only modest in young children, and the supply is variable. The cold-adapted live attenuated intranasal influenza vaccine might solve these problems, but it has been associated with postvaccination wheezing. In an international, multisite, industry-supported, randomized, double-blind trial, researchers compared intranasal vaccine and IM vaccine in 8352 children aged 6 to 59 months. Previously vaccinated children received one dose, and those who had never been vaccinated received two doses.

Culture-confirmed CDC influenza-like illness was significantly less common in the intranasal-vaccine group compared with the IM-vaccine group (153 vs. 338 cases; attack rates, 3.9% vs. 8.6%). In both vaccine groups, similar rates of infection were observed for two of three virus subtypes. Nasal stuffiness and low-grade fever were significantly more common in the intranasal-vaccine group. Fever higher than 102°F was uncommon in both groups. Overall rates of medically significant wheezing within 6 weeks of vaccination were similar in the two groups, in children with and without a history of wheezing. However, among children younger than 1 year, the incidence of medically significant wheezing was slightly higher in the intranasal-vaccine group (3.8% vs. 2.1%; P=0.08). Moreover, any-cause hospitalization within 6 months occurred more frequently with intranasal vaccine than with intramuscular vaccine in this youngest age group (6.1% vs. 2.6%; P=0.002) but not among older children.

Comment: Flu vaccine requires yearly administration and has been plagued by availability and efficacy problems. The cold-adapted live attenuated intranasal vaccine appears to be more effective than the IM vaccine, and concerns about vaccine-associated wheezing seem to have been overestimated in children older than 1 year. Time will tell if advisory groups will recommend intranasal vaccine for children.

— Howard Bauchner, MD

Published in Journal Watch Pediatrics and Adolescent Medicine February 14, 2007

Citation(s):

Belshe RB et al. Live attenuated versus inactivated influenza vaccine in infants and young children. N Engl J Med 2007 Feb 15; 356:685-96.

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• Medline abstract (Free)

Cox NJ and Bridges CB. Inactivated and live attenuated influenza vaccines in young children — How do they compare? N Engl J Med 2007 Feb 15; 356:729-31.

• Original article (Subscription may be required)
• Medline abstract (Free)