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26-01-2012 | Immunology | Article

Anaphylactic shock after vaccination 'extremely rare'


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MedWire News: Anaphylaxis is a very rare event following immunization, say researchers who detected no cases in a routine infant preschool immunization program that delivered more than 5.5 million vaccines.

Some older children had delayed onset of reactions, however, and this should be borne in mind when vaccinating those at higher risk for anaphylaxis, write Mich Lajeunesse (University Hospital Southampton NHS Foundation Trust, UK) and co-authors in the Archives of Disease in Childhood.

In their study, Lajeunesse and team sought to describe the incidence and clinical presentation of anaphylaxis as an adverse event following immunization (AEFI). This "is a rare adverse event and unlikely to be detected in prelicensure vaccine trials," they explain.

Using data from the British Paediatric Surveillance Unit, the team identified a total of 15 reports of AEFI in children aged 16 years and under in the UK and Republic of Ireland over a 13-month period.

Seven of the 15 reports met criteria for anaphylaxis as an AEFI under the Brighton Collaboration Case Definition, and each case had some form of allergic rash as part of a multisystem presentation. Interestingly, six of these children already carried injectable adrenaline for pre-existing atopic disease, multiple food allergies, and/or idiopathic urticaria with anaphylaxis.

A variety of vaccines were implicated in the reactions: three human papilloma virus vaccines (Cervarix), two single-component measles vaccines (Rouvax), a meningococcal C conjugate vaccine, a school leaver's booster (probably tetanus/inactivated polio virus), an inactivated typhoid vaccine (Typhim Vi), a quadrivalent meningococcal polysaccharide vaccine (ACWY Vax), and a hepatitis A vaccine (Havrix Junior Monodose).

The onset of symptoms was within 15 minutes in three cases and more than 30 minutes in four cases, with the most delayed reaction occurring at 120 minutes.

In terms of management, six children were treated with intramuscular adrenaline, three with intravenous fluids, one with salbutamol nebulisation. Only two received corticosteroids and five an H1 histamine receptor inverse agonist, while one child recovered without treatment.

Three cases attended Emergency Medicine Departments, four required acute pediatric services, and a further two were referred to pediatric outpatients. No child was admitted to intensive care and all children made a full recovery without sequelae.

In a separate analysis, Lajeunesse and co-workers analyzed information on all preschool and infant "routine" vaccines, including measles, mumps and rubella (MMR) and influenza vaccines delivered in the UK and Republic of Ireland over the same 13-month period.

"Approximately 5.5 million infants received routine vaccines without any reported cases of anaphylaxis," they state, adding: "This is extremely reassuring data for the general public and healthcare workers alike."

By Joanna Lyford

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