Vaccine injection technique and reactogenicity--evidence for practice.

There are inconsistencies in recommendations and practice with regards to how best to administer vaccines. This review evaluates the literature on intramuscular vaccine administration technique in primarily paediatric populations and concludes from available evidence which aspects of vaccine administration are associated with reactogenicity. Variables with best evidence to support practice to reduce reactogenicity were: Site of injection--less reactogenicity has been noted when the buttock is used rather than the thigh; tissue (muscle or subcutaneous)--less reactions are noted when vaccine is administered intramuscularly rather than subcutaneously; length of needle--longer needles are associated with less reactogenicity. Angle of injection--a 90 degrees angle is associated with less reactogenicity than a reduced angle. Despite a need for more empirical studies, there appears to be several vaccine administration techniques relating to needle angle, length, site and depth of injection that result in fewer reactions and these could be considered for public health policy, in conjunction with immunogenicity.