Immunization is highly effective in preventing infectious diseases and therefore an indispensable public health measure. Allergic patients deserve access to the same publicly recommended immunizations as non‐allergic patients unless risks associated with vaccination outweigh the gains. Whereas the number of reported possible allergic reactions to vaccines is high, confirmed vaccine‐triggered allergic reactions are rare. Anaphylaxis following vaccination is rare, affecting <1/100 000, but can occur in any patient. Some patient groups, notably those with a previous allergic reaction to a vaccine or its components, are at heightened risk of allergic reaction and require special precautions. Allergic reactions, however, may occur in patients without known risk factors and cannot be predicted by currently available tools. Unwarranted fear and uncertainty can result in incomplete vaccination coverage for children and adults with or without allergy. In addition to concerns about an allergic reaction to the vaccine itself, there is fear that routine childhood immunization may promote the development of allergic sensitization and disease. Thus, although there is no evidence that routine childhood immunization increases the risk of allergy development, such risks need to be discussed.

Recent clinical trials have demonstrated that new generation acellular pertussis vaccines can confer protection against whooping cough. However, the mechanism of protective immunity against Bordetella pertussis infection induced by vaccination remains to be defined. We have examined cellular immune responses in children immunized with a range of acellular and whole cell pertussis vaccines. Immunization of children with a potent whole-cell vaccine induced B. pertussis-specific T cells that secreted interferon-y (IFN-y), but not interleukin-5 (IL-5). In contrast, T cells from children immunized with acellular pertussis vaccines secreted IFN-y and/or IL-5 following stimulation with B. pertussis antigens in vitro. These observations suggest that protective immunity conferred by whole-cell vaccines, like natural immunity, is mediated by type 1 T cells, whereas the mechanism of immune protection generated with acellular vaccines may be more heterogenous, involving T cells that secreted type 1 and type 2 cytokines.

The mechanism of protective immunity against Bordetella pertussis generated following recovery from whooping cough in childhood has not yet been elucidated. Studies with a murine respiratory infection model have indicated that cellular immunity, mediated by Th1 cells, plays a role in the clearance of a primary infection with B. pertussis and in protection against subsequent challenge. In the present study, the induction of B. pertussis-specific Th cell subsets in children was examined. Peripheral blood mononuclear cells from B. pertussis-infected or convalescent children proliferated and secreted cytokines following antigen stimulation in vitro. In contrast, responses were weak or undetectable in the majority of children who had not been infected or vaccinated. In all cases, responding T cells produced interferon-gamma but low or undetectable interleukin-5. The findings suggest that Th1 cells may play a role in protective immunity generated following infection with B. pertussis in children.

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