Influenza vaccination of children is only justified when there is a risk of serious
influenza complications. In 2012, a live
attenuated vaccine for
intranasal administration was authorised in the European Union for
influenza prevention in individuals aged from 2 to less than 18 years. This type of
vaccine has been available in the United States since 2003. Clinical evaluation of this live
vaccine is based on three non-inferiority trials versus an injected
inactivated vaccine. There are no specific trials in children at risk of serious
influenza complications. Only one of these trials was double-blinded. Two trials involved children with a history of respiratory problems. Symptomatic
influenza confirmed by viral culture was less frequent in these three trials after intranasal vaccination than after injection of the conventional
vaccine (about 3 to 5% and 6 to 10%, respectively). There was no difference between the
vaccines in terms of clinical complications of
influenza, especially
asthma exacerbations. Adverse effects attributed to the intranasal
vaccine mainly consisted of local reactions such as rhinorrhoea and nasal congestion, as well as flu-like syndromes.
Wheezing,
respiratory tract infections and hospitalisation were more frequent with the intranasal
vaccine than with the injected
vaccine in children aged less than 1 year and in children with a history of severe respiratory illness. The intranasal
vaccine is contraindicated in these children. The intranasal
vaccine contains live attenuated virus strains and is therefore contraindicated in immunocompromised patients. US pharmacovigilance data suggest that severe
allergic reactions to the intranasal
vaccine,
Guillain-Barré syndrome, and transmission of
vaccine viruses to contacts are very rare.
Intranasal administration seems to be more practical, especially for children. In practice, there is no firm evidence that this live attenuated
influenza vaccine has any clinical advantages over injected
vaccines, including in children at risk of
influenza complications. In addition, this
vaccine is unsuitable for the very children who are most in need of protection against
influenza. It is better to stick with injected
influenza vaccines.