Where Should Vaccines be Given?

Dr. Parang Mehta, MD.

Vaccine injections must be given correctly for full benefit.  The timing, placement, and injection technique are all crucial to successfull vaccination.

Sometimes, vaccine injections are given at sites that have been shown to be associated with poor immune response.  The child suffers a painful prick, without the full benefit due.  The family assumes immunity from the disease in question, when in fact the child may be unprotected, because of faulty injection technique.

What's the correct place?

There are two actually - the shoulder, and the front of the thigh.  The old favorite, the buttock, has been abandoned now because of a higher rate of local side effects and poor immune response to vaccination.

The difference is in the fat and muscle layers.   Muscle layers lie deep, fat layers are just beneath the skin.  Muscles are well supplied with blood vessels, and any drug or vaccine delivered into it is quickly and completely absorbed.  Fat, on the other hand, is poorly supplied with blood vessels, and does not contain the cells required to start the immune response to a vaccine.

For best results, the vaccine must be delivered into the muscle.  This can be reliably done on the shoulder and thigh, but the thick layer of fat at the buttock makes it difficult.  If the vaccine is given into the fat, it is poorly absorbed, and the immunity produced is poor and short lasting.  This has been proved for hepatitis B, rabies, and influenza vaccines, and is probably true for other vaccines as well.

Apart from this consideration, the safety factor is important too.  The buttock hosts the sciatic nerve, which can be damaged by an injection given here, leading to partial loss of function of that leg.  While injections into muscle are safe, injections given into fat often result in abscesses and granulomas.  Vaccines containing aluminium salts (such as the DTP vaccine, hepatitis A, and hepatitis B vaccines) frequently cause local irritation, pain, and swelling when accidentally given into fat.

Last Revision: February 11, 2016