How the U.S. is stretching the monkeypox vaccine supply

A less common injection method allows a single dose to be split into five

As the monkeypox virus continues to spread in the United States, the Biden administration has adopted a strategy of vaccine-splitting to stretch the nation’s limited supply. A method known as intradermal vaccination allows a single-use vial to be split into five injections.

Subcutaneous

injection dosing

Intradermal

injection dosing

Subcutaneous

injection dosing

Intradermal

injection dosing

Bavarian Nordic makes Jynneos, the only monkeypox-specific vaccine approved in the United States. It was initially approved by the Food and Drug Administration for a single 0.5 milliliter subcutaneous injection, followed by a second 0.5 milliliter dose four weeks later.

Here is a look at the difference between a subcutaneous and intradermal injection.

SKIN CROSS SECTION

Epidermis

Dermis

Subcutaneous

tissue

Not to scale

SKIN CROSS SECTION

Epidermis

Dermis

Subcutaneous

tissue

Not to scale

SKIN CROSS SECTION

Epidermis

Dermis

Subcutaneous

tissue

Not to scale

SKIN CROSS SECTION

Epidermis

Dermis

Subcutaneous

tissue

Not to scale

Epidermis

Dermis

Subcutaneous

tissue

Not to scale

Epidermis

Dermis

Subcutaneous

tissue

Not to scale

Epidermis

Dermis

Subcutaneous

tissue

Not to scale

Epidermis

Dermis

Subcutaneous

tissue

Not to scale

Epidermis

Dermis

45

Subcutaneous

tissue

0.5 ml

of vaccine

injected

Not to scale

Epidermis

Dermis

45

0.5 ml

of vaccine

injected

Subcutaneous

tissue

Not to scale

Epidermis

Dermis

45

0.5 ml

of vaccine

injected

Subcutaneous

tissue

Not to scale

Epidermis

Dermis

45

0.5 ml

of vaccine

injected

Subcutaneous

tissue

Not to scale

The goal of a subcutaneous injection is to inject the vaccine into the subcutaneous tissue below the dermis layers.

A needle is inserted at a 45-degree angle.

This method is relatively easy to do and does not require much training. Vaccines injected into this layer absorb more slowly than other methods.

In contrast, intradermal vaccinations aim to deliver vaccine into the thin layer of the epidermis near the skin surface.

To get the needle into this tight space, it needs to be angled between five and 15 degrees.

Performing this method requires considerable skill and training and is not easily performed. It is rarely used for vaccinations and more often associated with allergy tests.

One benefit of this approach is that vaccines are absorbed much faster and may elicit a higher immune response, so less vaccine may be needed to get the same result as a subcutaneous injection.

When administered, the injected vaccine leaves a small blister, called a bleb, under the skin. Its presence confirms that the needle was properly inserted. The blister eventually scabs over.

The FDA approved intradermal vaccinations of the monkeypox vaccine citing a research study from 2015 on the method’s effectiveness.