Intramuscular injection angle: evidence for practice?

This article presents the findings of a search for evidence to support the 45-60 degree angle of insertion for intramuscular injection of vaccine which is recommended in New Zealand. With the objective of discovering the evidence base for an intramuscular injection angle which differs from that recommended by the World Health Organisation and the accepted practice experienced by the author in the UK, Canada, Malawi and the USA, a comprehensive library and internet literature search was undertaken. As well, information was sought by personal correspondence and contact with a range of immunisation specialists. Both the literature specifically on needle angle and that which includes needle angle within a wider investigation of technique is included. Overwhelmingly the evidence supports a 90 degree angle of needle insertion for intramuscular injection as being that most effective in terms of patient comfort, safety and efficacy of vaccine.