CDC's mpox alert for summer puts focus on JYNNEOS vaccine: What to know, who is eligible

Lack of testing, rationed vaccine doses, and weeks of painful quarantine characterized last year's outbreak of mpox, then known as monkeypox.

But a recent cluster of cases in Chicago, which triggered an alert from the Centers for Disease Control and Prevention, was quickly controlled with ample testing and vaccinations.

“The fact that this (Chicago) outbreak did not spread … shows that we’re in a very different place than a year ago,” said Dr. Jason Zucker, an infectious disease specialist at Columbia University.

Health officials urge Americans to protect themselves against mpox this summer, but unlike COVID-19 and influenza, not everyone is eligible to get vaccinated.

Here are some key facts about the vaccine and who can get it.

What to know about the mpox vaccine, JYNNEOS

The JYNNEOS vaccine, developed by Bavarian Nordic, was approved by the Food and Drug Administration to prevent mpox and smallpox in adults in 2019 and authorized under emergency use for people under 18 in 2022.

The vaccine is delivered in two doses that are given 28 days apart.

There are two ways to administer the shot:

• Standard: Injected into the fatty tissue right before the muscle (subcutaneously) with .5mL of vaccine.

• Alternative: Injected underneath the skin (intradermally) with .1mL of vaccine. Because less vaccine is needed, using this method increases the number of available doses by up to five-fold.

While adults can receive either method of administration, teens can only get their shot the standard way.

Both methods elicit similar protection, said Dr. David Diemert, clinical director of the George Washington University’s vaccine research unit and professor of medicine at the university’s School of Medicine & Health Sciences.

Who can get the mpox vaccine?

The CDC does not recommend the vaccine for the general public and instead urges health care providers to offer it to people at high risk for exposure.

Those at higher risk include people who were exposed to someone who tested positive for mpox or people who have had sexual contact in the past two weeks with someone who was diagnosed.

Others at high risk include: People who are gay, bisexual or men who have sex with men and transgender or nonbinary people who have been diagnosed with a sexually transmitted disease in the past six months. People who have sexual contact at commercial sex venues and sex workers are also at risk.

If I got the mpox vaccine last year, should I get it again?

Those who got a full series, or two doses, of mpox vaccine last year do not need a booster, according to the CDC.

For those who may have gotten only one dose last year, Zucker said they can get their last dose now without restarting the series.

So far, data shows people who received a full series of the vaccine still have a “high sustained antibody response” a year later and don't need a booster, Diemert said.

Unlike the virus that causes COVID-19, which requires boosters and vaccine iterations to keep up with mutations, pox viruses don’t mutate quickly enough to escape vaccine-induced immunity.

“We don’t get boosters for every vaccine,” Zucker said. For example, the measles, mumps and rubella (MMR) vaccine “you get in childhood, and you’re considered protected for most of your life.”

The vaccine technology used for the mpox shot, called a live attenuated virus, also “tends to produce more robust immune response and protection,” compared to other types of vaccines where antibody levels typically wane over time, Diemert said.

While data shows sustained antibody levels, health experts are quick to point out that people might still be at risk in the future. Studies suggest the vaccine remains protective for at least two years but experts say more research is needed.

What are mpox symptoms?

Symptoms include a rash, possibly on the hands, feet, chest, face, mouth and near the genitals, the CDC says on its website. The agency says the mpox incubation period is three to 17 days, and during this period, people won’t have symptoms and may feel OK.

Contributing: Saleen Martin, USA TODAY. Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: Mpox alert puts focus on JYNNEOS vaccine: Here's who is eligible