Anaphylaxis following immunization rare
MedWire News: Research suggests that anaphylaxis is a rare reaction to childhood immunizations.
"This is extremely reassuring data for the general public and healthcare workers alike," say Michel Erlewyn-Lajeunesse (University Hospital Southampton, UK) and colleagues.
The possibility of putting a child at risk for having an acute anaphylactic reaction to a vaccine has caused concern among parents and healthcare workers, but data regarding frequency of such reactions are sparse.
Erlewyn-Lajeunesse and team followed up children under the age of 16 years with suspected anaphylaxis as a result of immunization. The cases were reported through the British Paediatric Surveillance Unit (BPSU) between September 2008 and October 2009.
The team believes this is a fairly accurate representation of the amount of cases in the UK and Ireland, as all consultant pediatricians in these two areas were sent cards to fill out and send back regarding incidence of rare disorders or reactions to drugs with a "nothing to report" option also included. The return rate of these cards in the UK was 93.2% and in Ireland was 91.8% during the 13 months of the study.
In total, 15 cases of suspected anaphylaxis were reported during the study period, but only seven met full criteria for anaphylaxis (Brighton Collaboration Case Definition [BCCD]). The BCCD has three diagnostic levels for anaphylaxis with 1 being the most sensitive and specific and 3 the least.
Of the seven children with confirmed anaphylaxis, three were BCCD level 1, three level 2, and one level 3. All the children had some form of rash as part of the reaction and symptom onset varied from within 15 minutes (3 cases) to within 120 minutes (1 case).
Regarding vaccination type, the human papillomavirus (HPV), measles, meningitis C, typhoid, hepatitis A, and tetanus/polio vaccines were all implicated.
The investigators say that their results suggest that "anaphylaxis remains a rare adverse event following immunization."
The small number of events made calculating overall incidences difficult, but they estimated that the incidences of anaphylaxis in children given the single component measles vaccine and the HPV vaccine were 12.0 cases per 100,000 and 1.4 cases per 1,000,000 vaccinations, respectively.
"There is a clear need for international surveillance using standardized methodologies and case definitions," write Erlewyn-Lajeunesse et al in the Archives of Disease in Childhood.
"Some children had delayed onset of symptoms and this should be considered in those at higher risk of anaphylaxis," they note.
By Helen Albert