Monkeypox vaccines are now administered intradermally. What does this mean?

Key exclusions

  • In order to extend the limited availability of Jynneos monkeypox vaccine, the FDA has granted emergency approval for the vaccine to be administered percutaneously.
  • A dose-saving strategy allows providers to immunize five people with a single shot vial.
  • A lower dose is given under the skin, rather than deep into the fatty tissue typical of this vaccine.
  • Other vaccines and tests are given intradermally, and this is a safe and effective method.

Monkeypox is on the rise, and the U.S. does not have enough vaccines to protect everyone at high risk of contracting the disease.

To expand existing supplies of the monkeypox vaccine, known as Ginneos, the Food and Drug Administration (FDA) announced on August 10 that providers can use single-dose vials to administer five vaccines.

A small dose should be applied to the uppermost layer of the skin, not the underlying fatty tissue. This method is called intradermal vaccination.

There are at least 1.6 million people in the United States who are considered to be at high risk for monkeypox. At least 3.2 million doses of the two-dose vaccine are needed to protect this group. Only about half of this amount is expected to be available by the end of the year.

The dose-saving approach allows the government to make thousands of doses available for use by millions of people. But the data supporting the move comes mostly from a single study, and some experts are concerned that the new strategy will adequately protect vaccines.

What to expect from an intradermal vaccine

Most common vaccines in the US are given intramuscularly, or into the muscle layer beneath the skin and fat. For these types of injections, the needle meets your arm at a 90-degree angle. For example, the COVID-19 and flu vaccines are intramuscular injections.

Jynneos was initially approved in 2019 for another route of administration: subcutaneously. The subcutaneous layer of your skin, also called the hypodermis, is made up of fat and other tissues. It is the deepest of the three layers of skin and is an ideal site for injectable drugs such as insulin, epinephrine, and morphine. Since this is not as deep as your muscle, the needle is placed at a 45-degree angle for injection.

Very good / Mira Norian


The new emergency use authorization for monkeypox provides for subcutaneous injection only in minors. Anyone 18 years of age and older who is eligible for the vaccine will receive 0.1 milliliters of Jyneos – one-fifth of the initial dose – subcutaneously.

Jynneos is a two-dose vaccine. The CDC says people who receive a single dose of a standard subcutaneous shot, such as those under 18, may receive a second intradermal injection.

Intradermal injections deliver the vaccine or drug to the dermis, the topmost layer of the skin. This method is relatively rare because it is difficult to do correctly. But you may have had injections into the skin before. It is often used to test for tuberculosis and allergies.

Very good / Mira Norian


Intradermal injections are much shallower than subcutaneous or intramuscular injections. Keeping your skin intact, the healthcare provider inserts the needle into the dermis at a 5- to 15-degree angle. You will feel a quick pinch.

In the video explanation, the CDC says to give the vaccine until there is “noticeable, pale skin.” The resulting small, vaccine-filled hole should disappear within a few days.

Why Intradermal vaccination works with less vaccine

Vaccines work by introducing a foreign substance called an antigen into the body. This antigen prompts the immune system to produce antibodies and other specialized cells that recognize and attack the antigen when it encounters it again, such as a viral infection.

When someone is vaccinated, some cells near the site of vaccination carry the antigen to immune cells deeper in the body. This starts the body’s defense process.

Dendritic cells, abundant in the skin, rapidly deliver antigens to immune cells. Because of the effectiveness of these cells, intradermal vaccination produces an immune response faster than other methods, while using less vaccine, said Paul Offit, MD, director of the Vaccine Education Center and attending physician in the infectious diseases department at Children’s Hospital. From Philadelphia.

But does it work enough?

The FDA’s decision to switch to a dose-saving strategy was largely based on a 2015 study of approximately 523 participants, in which 191 participants received Jynneos intradermally.

This study measured the levels of neutralizing antibodies produced by different vaccination methods. Antibody levels are a key indicator of how well a vaccine is working. But these types of studies don’t always predict how well a vaccine will work in real-world settings.

Offit said researchers need to see how protective the dose-saving strategy is in people who receive the vaccine intradermally.

There is also a high probability of making a mistake when injecting the vaccine into the skin. If the needle is too sharp, the low-dose vaccine will be delivered too deeply and its effectiveness will be reduced.

“The FDA recommends studies conducted under controlled conditions,” Offit said. “Once you put it into the real world, there are people who are better and people who are not so good at skin grafting.”

Bavarian Nordic, the manufacturer of Jynneos, said it was somewhat hesitant about the data supporting the intradermal approach.

Bavarian Nordic President Paul Chaplin wrote a letter to the FDA commissioner and the Secretary of Health and Human Services following the decision to distribute the doses. The company, he wrote, “fully supports dose-saving approaches such as delaying the second vaccination,” but it has “some reservations” about the intradermal approach.

Still, Chaplin said the company would work with U.S. officials to pursue approval and continue to conduct research on the safety and effectiveness of various vaccination methods.

How side effects compare

According to the FDA, the side effects of Jynneos were similar in people who received the injection subcutaneously and those who received the injection intradermally, and none of the reported side effects were severe.

In a 2015 study, fatigue was the most common side effect regardless of whether Jynneos was administered. Each group reported similar levels of muscle pain, chills, headaches, and other side effects.

Participants who were injected with Jynneos intradermally had more itching and redness that lasted for two weeks.

“We don’t really know what that means for long-term protection, and we don’t really know what that means for safety,” said Ellen Carlin, DVM, assistant research professor at Georgetown University’s Center for Global Health Science and Security. , said a statement to Verywell. “We know that there have been more injection reactions here [intradermal] group of people”.

Is a small dose better than a single dose?

In mid-July, some countries delayed the second dose of Jynneos to get at least one shot of as many weapons as possible with their limited supply.

The FDA said the method was “unacceptable.” But research shows that a single dose can induce a strong and long-lasting immune response.

Scientists don’t know much about how well any of the vaccination strategies work in the real world. This is because Jynneos is licensed based on data from animal experiments and human immune response studies. However, due to logistical and ethical concerns in conducting monkeypox clinical trials, there have been no large-scale studies of the incidence of disease in vaccinated individuals compared to a placebo group.

If the vaccine regimen primes the immune system to mount a strong defense against the monkeypox virus, scientists expect it to protect against severe disease.

science The National Institute of Allergy and Infectious Diseases says it will begin a randomized control trial in September to test how well two-fifths of a dose compares to two full doses. But this study only examines the immune response, rather than how well vaccines protect against disease.

Offit says that once people are vaccinated, they may believe they are protected against monkeypox and be less cautious about behaviors that spread the virus, including sex. If a lower dose proves ineffective, such as a subcutaneous shot, the disease may continue to spread at a higher rate.

What does this mean for you?

If you’re eligible for the monkeypox vaccine, be aware that it may be different from other shots you’ve received in the past. This is because the vaccine only penetrates the top layer of your skin, not the muscles or deeper layers of skin that are targeted by other vaccines and injectables. Scientists are not sure how effective this intradermal method will be.

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