Since the start of the monkeypox outbreak, many people have reported side effects of the Jynneos vaccine, including a red bump that forms at the injection site and lingers for several weeks—but experts have said that this "super common" reaction is not "weird" or "permanent," Patrick Ryan reports for USA Today.

The 'super common' reaction to the monkeypox vaccine

A growing number of social media users have reported a red bump that appears at their Jynneos vaccine injection site, which typically lasts two to three weeks.

The lump from my monkeypox vaccine continues to grow and I'm beginning to fear that it is learning. pic.twitter.com/YI2xpivqDg

— No Blaine No Gain (@Whataboutblaine) July 27, 2022

:( monkey pox vax bump :( pic.twitter.com/tkiai0SVEO

— The Gay Hashira ⚔️ (@Lux_ternity) July 21, 2022

In addition, some people have experienced tenderness, itching, pain, or bruising on or around the bump.

Given the global shortage, I am very grateful to have been able to get my monkeypox vaccine. This is my 2nd dose, which was given intradermally (1st was given subcutaneously). 1st shot resulted in a small bump, about the size of a nickel; this one is about the size of an egg lol. pic.twitter.com/wbLBwl8J1x

— Kenneth Gavina, PhD (@KennyGPhD) August 20, 2022

"So many people are having inflammation at the site for many weeks," said Anthony Fortenberry, CNO at Callen-Lorde Community Health Center.

Should you be concerned about side effects?

Experts have reassured Jynneos recipients that this common complaint is not a "weird" or "permanent" reaction.  The Jynneos vaccine has produced side effects that "are comparable to most other vaccines," with reactions that are "generally far milder than what some experienced with the COVID-19 vaccines," said Aditya Chandorkar, an assistant professor in the division of infectious diseases and international medicine at the University of Minnesota.

According to Fortenberry, a temporary lump forming at the injection site is normal for many vaccinations, however "it is particularly expected with the Jynneos vaccine … This is a super common side effect" and should not deter people from getting their second doses.

"The original (Jynneos) vaccine studies reported some degree of local swelling in over half of the people who received the vaccine," said Chandorkar.

"The body recognizes the viral material as foreign and sends immune cells to react against it," Chandorkar added. "One of the consequences of this reaction (is) some degree of local reaction, leading to a lump/swelling."

"For inflammation to occur for up to four weeks is such an expected side effect that clinical guidance (at vaccination sites) addresses that, by asking nurses to administer the shot on the other arm," Fortenberry said.

However, "It's important to note that the presence or absence of the swelling is not a marker for how well the person is going to be protected by the vaccine," Chandorkar said.

Regarding the itching, pain, or tenderness around the injection site, "That generally does resolve on its own," Fortenberry said. "You do want to avoid scratching it because that can cause further inflammation, delay healing and also cause infection, so you want to be cautious. And if it's causing pain, the recommendations are over-the-counter Tylenol or Motrin" to ease inflammation. 

According to Chandorkar, "[o]ther side effects [of the Jynneos vaccine] include muscle pain, headache, fatigue and nausea … Although fevers and chills are reported, they are not the norm. They are only seen in 1 to 10% of patients," he noted.

Still, Peter Hotez, co-director of the Center for Vaccine Development at Texas Children's Hospital and dean of the National School of Tropical Medicine at Baylor College of Medicine, said people should reach out to a medical professional if they experience fever or chills that persist more than one to two days after getting vaccinated.

According to Hotez, "if the pain [from the bump] becomes problematic, or if you see the redness worsen or spreading, including streaks of redness, you should contact your doctor."

While severe reactions to Jynneos are "extremely rare," Fortenberry urged individuals to call 911 immediately if they have trouble breathing, hives, swelling of the face or throat, a fast heartbeat, dizziness, or weakness after getting Jynneos. (Ryan, USA Today, 8/24)