I would question giving five injections in one sitting. There is no way to tell what is causing an allergic reaction. Yes, the vastus lateralis is the only site that I am familiar with for IM injections of babies.
"The acceptable injection sites for infants include both the vastus lateralis (outer thigh) and the ventrogluteal muscle. Unfortunately, many health professionals are unfamiliar with the ventrogluteal or hip site and confuse it with the dorsogluteal or buttock site. The latter should not be used until the child has been walking in order to develop the muscle mass. The dorsogluteal site is dangerously close to the sciatic nerve and is covered with abundant subcutaneous tissue in many people. Its landmarks, especially the outer boundary, are poorly defined. I do not recommend this site unless no other muscle area is available for an IM injection."
EHS: WOW-Ventrogluteal Site for Intramuscular Injections
This is Donna Wong's site who is the author of well-known peds nursing texts.
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