With the exception of BCG and sometimes rabies and IPV,all parenteral vaccines are given by either intramuscular (IM) or subcutaneous (SC) route. The SC route is recommended for measles, MMR, varicella, meningococcal polysaccharide, Japanese encephalitis (JE), and Yellow fever vaccines; either SC or IM route may be used for pneumococcal polysaccharide vaccines, such as IPV; the rest of the vaccines should be given intramuscularly. Generally speaking, there is no harm done if SC vaccines are given IM. However, vaccines designated to be given IM should not be given SC due to risk of side effects (as seen with aluminum adjuvanted vaccines) or reduced efficacy (due to reduced blood supply in SC tissue and hence reduced immunogenicity). The gluteal region should never be used for administration of IM injections due to risk of sciatic nerve injury and reduced efficacy (rabies and hepatitis B vaccines). When used at the recommended sites where no large blood vessels exist, pulling back of the syringe to check for blood is not recommended. The needle should be withdrawn a few seconds after finishing administration of the vaccine (to prevent backflow of vaccine into the needle track) following which the injection site should be pressed firmly for a few seconds with dry cotton. The injection site should not be rubbed following injection.
If multiple vaccines are administered at a single visit, administration of each preparation at a different anatomic site is desirable. For infants and younger children, if more than two vaccines must be injected in a single limb, the thigh is the preferred site because of the greater muscle mass; the injections should be sufficiently separated (i.e. 1 inch or more if possible) so that any local reactions can be differentiated. For older children and adults, the deltoid muscle can be used for more than one IM injection (Table 1). If a vaccine and an immune globulin preparation are administered simultaneously [e.g. Td/ Tdap and tetanus immune globulin (TIg), hepatitis B and hepatitis B immunoglobulin (HBIg)], separate anatomic sites should be used for each injection. The location of each injection should be documented in the patients’ medical record (Figs. 1 to 4).