Some people who have received the monkeypox vaccine are noticing a small, raised bump that appears at the injection site. If this happens to you, and the mark lingers for days or even weeks, there’s no need to be alarmed: It’s called a wheal, a totally normal reaction that should be expected. And, yes, there’s a reason you’re only hearing about this now, months after the monkeypox vaccine rollout began.
In early August, the Biden administration declared the monkeypox outbreak a public health emergency to increase efforts in curbing the climbing case count, which has topped 16,900 at the time of publication, per the Centers for Disease Control and Prevention (CDC). Prior to the declaration, the preferred monkeypox vaccine, called Jynneos, was given subcutaneously; this means it was injected into the fatty tissue directly under the skin, similar to the flu shot or the COVID vaccines, per the US National Library of Medicine (NLM). As long as monkeypox is considered a public health emergency, though, the vaccine can be given via an intradermal injection, which isn’t a very common method.
“Most vaccines are given as shots into the muscle or subcutaneous fat,” Kaitlyn Rivard, PharmD, infectious disease residency director at Cleveland Clinic’s pharmacy department, tells SELF. “The monkeypox vaccine is unique in that it is given as a shot under the first layer of skin.” Basically, the needle is injected closer to the surface of your skin, in between the outermost layers. This injection method should cause that raised, blister-like bump at the injection site.
So why change how Jynneos is administered now? Giving the monkeypox vaccine via an intradermal injection rather than subcutaneously is one way to help preserve the country’s supply of the vaccine, which is struggling to keep up with demand due to the pace of the spread. “This approach could increase the number of available Jynneos vaccine doses by up to five-fold,” a CDC statement says. Administering it subcutaneously requires 0.5 milliliters of the vaccine whereas an intradermal injection requires just 0.1 millimeters, a difference that should ultimately help get vaccines to the most vulnerable people.
So what is a wheal, anyway? And when can you expect it to go away? Ahead, experts explain what you need to know about this vaccine side effect.
Why does a wheal develop after the monkeypox vaccine?
The wheal is caused by the actual contents of the vaccine, Dr. Rivard explains. “The liquid from the vaccine creates a bubble under this shallow layer of skin, which is why it is noticeable,” she explains. “The bubble should look like a pale elevation of skin,” and so it will be similar to the color of your skin tone. While you may understandably be curious about it, there’s no need to fret over this side effect, per Dr. Rivard: “A wheal is a normal occurrence after an intradermal injection, and there is no need to worry.”