Anaphylaxis and the Influenza Vaccine

More than a dozen studies over the past few decades have undermined the once common fear that influenza vaccines containing egg proteins could induce reactions such as anaphylaxis in people with egg allergies.

More than a dozen studies over the past few decades have undermined the once common fear that influenza vaccines containing egg proteins could induce reactions such as anaphylaxis in people with egg allergies.

But a new paper published in the Journal of Allergy and Clinical Immunology: In Practice may provide the final piece of missing evidence that dispels remaining worries.

All prior studies had investigated the effects of injectable inactivated influenza vaccines (IIV) rather than intranasally administered live attenuated influenza vaccine (LAIV), which is also grown in eggs and contains a small amount of residual egg protein (<0.24 μg/dose).

The new study; however, tracked the effects of LAIV on both 55 children with no history of egg allergy and 68 children (median age, 6.5 years) who had already suffered allergic reactions within one hour of egg ingestion and tested positive for specific IgE antibody to egg protein.

All of the patients received a normal dose of LAIV and remained under observation for the next hour. No patient from either group exhibited any sign of reaction during that period, and, when researchers followed up by telephone 24 hours later, they found again found no sign of any allergic reactions.

“Thus, it appears that the use of LAIV in children with egg allergy is safe,” wrote John M. Kelso, MD, in a review piece that accompanied the study. “This is particularly important because this year, for the first time, for the 2014 to 2015 influenza season, LAIV is preferred over IIV for children ages 2 to 8 years due to its superior efficacy”.

Kelso’s piece noted that influenza vaccines were specifically contraindicated for people egg allergies until just a few years ago, simply because it seemed logical that the small amounts of egg protein might be enough to trigger attacks.

“As recently as 2010,” he wrote, “the notion that patients with egg allergy could be given the influenza vaccine as a single dose without prior vaccine skin testing was so controversial that a ‘Clinical Pearls’ article in the Journal of Allergy and Clinical Immunology that proposed this had to be relabeled an ‘Editorial.’ “

However, public research never indicated that vaccines created problems. Indeed, a recent review found 28 studies that examined the effects of influenza vaccination on a total of 4,315 subjects with documented egg allergies. Among all those people — including 656 with a history of egg-induced anaphylaxis — no serious reactions occurred.

Such consistent results began shifting policy in 2011, when the Advisory Committee on Immunization Practices recommended that people with mild egg allergies receive a normal vaccination from any caregiver and stick around for 30 minutes of observation. Those who suffered severe reactions were advised see an allergist about vaccination.

The committee later decided, and the Joint Task Force on Practice Parameters agreed, that the evidence of safety had become so overwhelming that all people with egg allergies could safely get vaccinated anywhere without any subsequent observation.

Still, many vaccine creators continue to list egg allergies as a contraindication on product labels, and recent research suggested that some patients (or their parents) and some doctors still have reservations despite the very real risk (particularly to children) of neglecting such vaccines. Influenza sends 20,000 American children to the hospital each year and kills more than 100 of them.