SAN FRANCISCO (KRON) – Long lines waiting for vaccine doses have become one of the most indelible images of this year’s global monkeypox outbreak, which in just a few months has led to over 20,000 worldwide cases ⁠— including 5,811 cases in the United States.

Monkeypox and smallpox, both of the orthopoxvirus family, are so closely related that both licensed vaccines for smallpox prevention are believed to work for both. But smallpox vaccination has not been routine in the U.S. since 1972, when the disease was considered eradicated here.

The vaccine being given to prevent monkeypox, Jynneos, was approved in 2019 for the prevention of smallpox and monkeypox. Danish company Bavarian Nordic is the only one that can produce it.

So what of ACAM2000, the other vaccine that could do the trick?

What is ACAM2000?

ACAM2000 was approved in 2007 by the U.S. Food and Drug Administration, and replaced Dryvax as the nation’s go-to smallpox vaccine. (Dryvax was used to help contain the 2003 U.S. monkeypox outbreak.) ACAM2000 contains live vaccina virus, which is not smallpox, but is closely related.

Just a few years earlier, there were widespread fears that then-Iraqi dictator Saddam Hussein was making or stockpiling smallpox, according to the Associated Press. Though Hussein had used chemical weapons during the Iran-Iraq War and in at least two massacres inside Iraq, no smallpox was found after the U.S.-led invasion in 2003.

Smallpox was eliminated as a naturally-occurring virus in 1980, though there are viral samples in the U.S. and Russia.

According to the FDA website, “The approval and availability of this second-generation smallpox vaccine [ACAM2000] in the Strategic National Stockpile (SNS) enhances the emergency preparedness of the United States against the use of smallpox as a dangerous biological weapon.”

There are about 100 million doses of ACAM2000 in the Strategic National Stockpile, according to a July 1 press release from the U.S. Department of Health and Human Services. In comparison, the U.S. has only secured 1.1 million doses of the two-dose Jynneos vaccine, according to HHS Secretary Xavier Becerra.

Why isn’t ACAM2000 being used for monkeypox?

California State Sen. Scott Wiener mentioned the potential for ACAM2000’s use in an interview with Nexstar’s KRON, saying “that is an option,” but casting doubt on whether it would happen.

“That is an option,” Wiener told KRON. “The challenge with it is it’s very complicated to administer it. It’s numerous shots, it’s not just like one, so you have to do a whole bunch of injections at the injection site, and because it’s a live virus, it could have significant side effects. For healthy people, they’ll almost certainly be fine, but it does have significant side effects, and the site of the vaccination can be contagious for the virus that is used in the vaccine, so people have to cover it, be very protective of other people in their household.”

He continued: “If we really, really needed to, we do have the option of tapping into that stockpile and vaccinating a whole bunch of people with an effective vaccine, and I know that our state and local health authorities have thought about that, but it’s not ideal. It’s more of a desperate, last resort.”

The U.S. Centers for Disease Control and Prevention said the ACAM2000 vaccine “is available under an expanded access investigational new drug protocol sponsored by CDC for vaccination of individuals at risk of monkeypox infection.”

“If there are requests from states or territories requesting the ACAM2000 vaccine, CDC will work to ensure that individuals are fully informed on the benefits and the risks before receiving the vaccine,” CDC spokesperson Kristen Nordlund said.

However, Nordlund highlighted other problems with the vaccine. “ACAM2000 carries greater risk of certain serious side effects than Jynneos and cannot be provided to individuals who are immunocompromised or who have heart disease.”

Particularly, people with eczema have a risk of severe disability or death, according to the FDA, due to the live nature of the vaccine. People with a human immunodeficiency virus infection or eye disease “should be identified and measures should be taken to avoid contact between those individuals and persons with active vaccination lesions,” the FDA states.

The total number of Americans needing vaccination due to exposure or risk factors is estimated by the CDC to be 1.6 million, which means the federal government will need about four times as many Jynneos vaccines as it has already secured in order to fully vaccinate the population at highest risk. With Spain becoming the first country outside Africa to report monkeypox deaths over the weekend, health officials are working against the clock.

What are the symptoms of monkeypox?

Symptoms of monkeypox include onset of flu-like symptoms and distinctive rashes or sores that could look like pimples or blisters. CDC statistics show the most commonly-reported symptoms are rash (99%), malaise (70%) and fever (64%).

While the red, flat spots can be anywhere on the body, they are most likely in the current outbreak to affect the genital or rectal areas, or the fingers, mouth or eyes. The spots become bumps, which break and crust over into a scab. They may be itchy, but not necessarily.

Further, some people only get one or some of these symptoms; it is possible to have a fever but never a rash, or have these symptoms sequentially and not concurrently.

Who can get a monkeypox infection?

Anyone could become infected with the monkeypox virus, San Francisco Department of Public Health spokesperson Noel Sanchez said.

CDC and SF Department of Public Health statistics show the current outbreak is primarily affecting men who have sex with men; though at least 13 U.S. cases as of July 25 have been diagnosed in people who were assigned female sex at birth.

The virus is spread through close skin-on-skin contact, and an adviser on sexually transmitted infections with the World Health Organization stated experts have not determined whether it is a sexually transmitted infection per se, though it is “clearly transmitted during sex.”

“While most cases resolve on their own without pills or treatment, monkeypox can be serious,” Sanchez said. “We are trying to contain outbreaks and reduce transmission to avoid the virus spreading to more people and potentially becoming endemic.”

Sanchez advises people to:

• cover exposed skin in crowds
• avoid sharing bedding and clothing
• talk with close physical and sexual contacts about health, rashes and sores
• be aware of symptoms