Hypersensitivity and vaccines: an update

Area of Science:

• Immunology
• Vaccinology
• Dermatology

Background:

• Allergic reactions to vaccines are diverse, including true allergies, pseudo-allergic reactions, and atopic symptom exacerbations.
• Pseudo-allergic reactions, potentially linked to hyperimmunization, are more common than true allergies.
• Atopic reactions can be mistaken for the 'flash' phenomenon, a threshold reduction in reactivity post-vaccination.

Purpose of the Study:

• To review and update current knowledge on vaccine-related allergic reactions and side effects.
• To provide guidance on managing specific vaccine reactions, including those to egg-based vaccines, tetanus, hepatitis, influenza, and BCG.
• To discuss adverse events associated with newer vaccines such as H1N1 and human papillomavirus (HPV).

Main Methods:

• Literature review of vaccine adverse events and allergic reactions.
• Analysis of clinical presentations and management strategies for various vaccine-induced reactions.
• Inclusion of updated guidelines and information on novel vaccine side effects.

Main Results:

• Frequent BCGitis has led to modified Bacillus Calmette-Guérin (BCG) vaccination guidelines, reserving it for high-risk individuals.
• Specific reactions discussed include urticaria after hepatitis vaccination, aluminum granuloma, and vasculitis post-influenza and BCG vaccination.
• The review covers assessment following tetanus vaccination reactions and vaccination strategies for egg-allergic individuals.

Conclusions:

• Accurate classification of vaccine reactions is crucial for appropriate management.
• Updated guidelines and awareness of potential side effects are necessary, especially with new vaccine introductions.
• This review offers a comprehensive overview of vaccine hypersensitivity and adverse events, aiding clinical practice.