A study led by doctors in Southampton and London has found a nasal spray flu vaccine is unlikely to trigger allergic reactions in children who suffer from egg allergy.
The spray, which is known as live attenuated influenza vaccine (LAIV), was also shown to be safe for those with well-controlled asthma or recurrent wheeze.
Egg allergy is common in early childhood and affects at least one in 50 pre-school children. As influenza vaccines are cultured in hen’s eggs and contain egg protein, they have previously been administered only to ‘high risk’ children, such as those with severe asthma.
However, in 2012, the Department of Health recommended annual vaccination of children aged two to 16 years of age as part of the NHS childhood vaccination programme to reduce the number of severe and life-threatening cases of flu-related illness among young people.
Although LAIV had been available in the United States for a number of years, there was no safety data available on its use in young people with egg allergy and/or asthma and some guidelines recommend against its use in children under five years with a history of recurrent wheeze or asthma.
As a result, clinicians led by Dr Mich Lajeunesse, a consultant paediatric immunologist at Southampton Children’s Hospital, set out to assess its safety in children with the conditions.
In an initial study carried out by the group in 2013, 282 children with egg allergy – 40% of whom had a history of severe reactions, known as anaphylaxis – were immunised and had no systemic or significant allergic reactions to LAIV.
While this research suggested the vaccine was likely to be safe, a larger multicentre trial – SNIFFLE 2 – was required to confirm the findings, with results published today by The BMJ.
A total of 779 young people aged two to 18 years with egg allergy were recruited from 30 UK allergy centres and immunised with LAIV.
Of the participants, 315 (40%) had experienced an allergic reaction to egg in the past 12 months, 270 (35%) had experienced previous anaphylaxis to egg and 445 (57%) had doctor diagnosed asthma or recurrent wheeze.
They were observed for at least 30 minutes after vaccination and followed-up by telephone 72 hours later, while those with a history of recurrent wheeze or asthma underwent further follow-up four weeks later.
No systemic allergic reactions occurred within two hours of vaccination. Nine participants (1.2%) experienced mild symptoms, including a skin rash, sneezing, itchiness and a blocked or runny nose, suggesting a local allergic reaction.
Delayed events potentially related to the vaccine were reported in 221 participants, but no participants were admitted to hospital and no increase in lower respiratory tract symptoms occurred in the four weeks after vaccination.
“This study confirms our previous findings that LAIV is unlikely to trigger a serious allergic reaction in young people with egg allergy,” said Dr Lajeunesse, co-chief investigator of the study alongside Dr Paul Turner of Imperial College London.
“It also provides evidence that, with the exception of children with severe anaphylaxis to egg which have previously required intensive care, children with egg allergy can be safely vaccinated with LAIV in any setting, including primary care and schools.
“Our advice excludes those with most severe egg allergy as this group was not part of the study and we need further work to establish that the vaccine is safe in these children but, fortunately, very few children are admitted to intensive care with anaphylaxis to any food, including egg.”
Dr Lajeunesse, who is a senior lecturer at the University of Southampton, added: “We also found the vaccine is appropriate for use in children at risk of wheeze whose symptoms are well controlled and have had no evidence of active wheezing in the 72 hours before immunisation.
“However, as is always the case in any setting where vaccination is provided, facilities and staff trained to recognise and treat anaphylaxis should be available.”
Posted on Tuesday 8 December 2015