Are there differences in immunogenicity and safety of vaccines according to the injection method?

Objective. - A literature review was made to answer the following question: are there differences in immunogenicity and safety of vaccines according to the administration route (intramuscular or subcutaneous) and the length of needles used for injection? Design. - The search strategy included electronic searching (Medline database via PubMed) and cross-references. Articles were selected by reading abstracts, guided by the clinical question. A total of 18 articles were selected and analyzed; 13 answered the question. Results. - Nine articles compared the immunogenicity and/or the safety of a given vaccine administered via both intramuscular and subcutaneous routes. All the results showed that immunogenicity and systemic safety of the intramuscular route was at least as good as that of the subcutaneous route. Local tolerance was usually better via intramuscular route (lower risk of developing erythema or edema). Four articles compared the immunogenicity and the safety of vaccines administered with short (16mm) and long (25mm) needles in children. Long, needles induced fewer local reactions, probably because they can reach more vascularized muscle, especially in overweight and obese patients. Conclusions. - Immunogenicity and safety results are in favor of intramuscular vaccination. The appropriate needle length must to be adapted according to the morphological aspects (subcutaneous tissue and muscle thickness). (C) 2008 Elsevier Masson SAS. Tous droits reserves.