A large international study suggests that giving infants and young children live flu vaccine in a nasal spray is more effective than injecting them with the more traditional inactivated vaccine.
The study is published in the New England Journal of Medicine.
Health advisory bodies in the US have recently recommended that children from 6 months to 5 years of age should have an annual flu shot based on the trivalent inactivated influenza vaccine.
The nasal spray form of live vaccine is not approved for this age range.
The motive for this study was to compare the effectiveness of the inactivated vaccine form with the live nasal spray form.
8,352 children in 16 countries were enrolled in the study, which took place in October 2004, and 7,852 of the records fulfilled the protocol criteria for inclusion in the analysis.
The children were randomly put into two groups, where one group had the live nasal spray form of flu vaccine and the other had the inactivated injection form. Children who had recently had a wheezing illness or sever asthma attack were not included in the trial.
The product used as the vehicle for the live form was the FluMist brand of nasal spray manufactured by MedImunne Inc who also paid for the study. The inactive form of the vaccine was administered using either Fluzone or Vaxigrip, both of which are manufactured by Aventis Pasteur.
To guarantee the “blindness” of the trial, the group that was given injections was also given a saline nasal spray and the group that was given the live nasal spray had saline injections.
The researchers found that 153 cases of flu (confirmed by culture sampling) occurred in the FluMist group, compared with 338 cases in the group that received the injected inactive form of vaccine. This translates to 55 per cent fewer cases in the FluMist group, and a highly statistically significant result.
In the FluMist group there were also 89 per cent fewer cases of A/H1N1 type flu and 79 per cent fewer cases of A/H3N2 type flu, compared with the injected inactive vaccine group. This was also a statistically significant effect. However, although there were 16 per cent fewer cases of type B flu in the FluMist group, this was not found to be statistically significant.
The study did find that among very young children, aged between 6 to 11 months, there was an elevated risk of wheezing occurring within 42 days of having the FluMist vaccination.
Also, although the rate of adverse events was much the same in the two groups, the FluMist group had a significantly higher rate of hospitalization, for any cause, than the injected inactive vaccine group.
The researchers concluded that “Among young children, live attenuated vaccine had significantly better efficacy than inactivated vaccine. An evaluation of the risks and benefits indicates that live attenuated vaccine should be a highly effective, safe vaccine for children 12 to 59 months of age who do not have a history of asthma or wheezing.”
FluMist, which has been approved in the US for people 5 to 50 years old, should now be approved for most children from 1 year onwards, said the study leader, Dr Robert Belshe, who is Director of the St. Louis University Center for Vaccine Development, in Missouri.
Representatives of the Centers for Disease Control and Prevention (CDC) wrote in an editorial accompanying the article that these results are encouraging, but they would want a closer examination of the safety data before issuing any further advice on the use of FluMist with younger children.
“Live Attenuated versus Inactivated Influenza Vaccine in Infants and Young Children.”
Robert B. Belshe, Kathryn M. Edwards, Timo Vesikari, Steven V. Black, Robert E. Walker, Micki Hultquist, George Kemble, Edward M. Connor.
NEJM, Volume 356:685-696, February 15, 2007, Number 7
Written by: Catharine Paddock
Writer: Medical News Today