Case discussion of an immediate serious reaction to hexavalent vaccine mistaken for anaphylaxis.

Anaphylaxis is rarely associated with vaccination. Clinical presentation may include a variety of non-specific symptoms, making a clinical diagnosis uncertain. Therefore, it is important to distinguish anaphylaxis from other adverse events following immunization (AEFIs), particularly in children, to manage subsequent immunizations where necessary. For administration of additional doses a specialist evaluation is recommended to confirm the diagnosis and consider if re-vaccination is appropriate. A post-event evaluation is based on an in-depth history and skin and in vitro testing to identify specific sensitizations. Applying a standardized AEFI case definition,such as the Brighton Collaboration [1], is also helpful for individual cases as well as pharmacovigilance activities. We describe the case of a child with an immediate reaction to hexavalent vaccine which was mistakenly diagnosed as anaphylaxis. The baby, born in the 34th week, reported no perinatal problems and was breast and artificial milk fed. In good health, he received the first dose of hexavalent vaccine (diphtheria-tetanus-pertussis-poliohepatitis B-haemophilus influenzae type B) at 3 months of age. Upon injection he cried, then he manifested atony, pallor,apnoea and flaccidity.Treated with mouth-to-mouth ventilation, he responded by crying, gasping, ocular reversion and generalized hypotonia. He was then treated with intramuscular epinephrine. On arrival in the emergency department. oxygen was admininistered and he became responsive, reactive and began to breathe normally. He was treated with i.m. methylprednisolone. A transient papular skin rash was observed on the trunk. The vaccination schedule was interrupted and he was referred to a specialized consultation service [2] for further vaccination. Serum analysis showed total IgE = 10 kU l-1 and IgE level to tetanus toxoid <0.10 kUA l-1 (Unicap, Phadia, Sweden). Since there were doubts about the anaphylaxis diagnosis, the following hypotheses were evaluated with international vaccine safety collaborators: