In 2013 the Department of Health introduced a new winter influenza (flu) vaccine for children over two years old. The vaccine uses a nasal spray instead of an injection and is called LAIV (Fluenz, Astra Zeneca). It contains small amounts of residual egg protein so had not been given to children with egg allergy. Egg allergy is one of the most common food allergies in childhood, with an estimated prevalence of at least 2% in preschool children, so this was a significant barrier to successful implementation of the immunisation program.
Recent research had shown that the old injected flu vaccine is safe when it has very low amounts of egg, even in people who have had severe allergic reactions to egg. Researchers from the SNIFFLE study thought that LAIV was also likely to be safe for people with egg allergy but needed to undertake a study to prove it.
The SNIFFLE study enrolled children aged 2 to 17 years old who had been diagnosed with egg allergy, including 186 children with a history of asthma. The children were given at least one dose of nasal flu vaccine between September 2013 and January 2014. The recommended second dose of vaccine was given to 151 of the children. The study found that children with asthma were not more likely to experience adverse events than the other children.
No systemic or severe allergic reactions were seen among 282 egg-allergic children (115 children had experienced prior anaphylaxis to egg) who received the vaccine. Eight children experienced mild reactions and twenty six experienced wheezing or coughing within three days. Findings of the study have been published in The Journal of Allergy and Clinical Immunology.
The study demonstrated that LAIV (supplied during the 2013-2014 influenza season) did not cause systemic allergic reactions in children with egg allergy, including those with a prior history of anaphylaxis, similar to that previously reported for children without egg allergy. The vaccine appears to be well tolerated in children with a diagnosis of asthma or recurrent wheeze.