Exposed to monkeypox? The smallpox vaccine can help


Note: On Nov. 28, 2022, the World Health Organization announced it will begin transitioning from the term "monkeypox," to "mpox," referring to the disease as both for a year while it completely phases out "monkeypox." "WHO will adopt the term mpox in its communications, and encourages others to follow these recommendations, to minimize any ongoing negative impact of the current name," the organization said. WHO is responsible for assigning names to new diseases.

The vaccine for an old scourge also protects against a newer threat

Monkeypox, a rare disease caused by a virus, is grabbing headlines lately. The first case in humans was identified in 1970. Since then, monkeypox has been found mainly in central and western Africa. Recently, however, cases have been reported in several countries, including the United States, where the virus does not normally circulate.

“Typically, we don’t see as many cases and as much person-to-person transmission in the United States as we are seeing with the current outbreak,” says Annabelle de St. Maurice, MD, MPH, an infectious diseases expert. Dr. de St. Maurice is Co-Chief Infection Prevention Officer for UCLA Health.

“The risk is still very low, however,” she notes. “If you do get exposed to monkeypox, treatment is available. One option for individuals with high risk exposures is vaccination with a smallpox vaccine.”

A vaccine with two-for-one benefits

How can one vaccine protect against two different diseases? The viruses that cause monkeypox and smallpox are closely related. Both belong to a genus called Orthopoxvirus.

“When you are vaccinated against a viral disease, your immune system makes antibodies and white blood cells to target that specific virus,” says Dr. de St. Maurice. “In this case, the viruses are similar so that protection against one also provides protection against the other.”

How to access the smallpox vaccine

Getting a smallpox vaccine isn’t quite as simple as getting a COVID-19 vaccine or flu shot. Routine vaccination against smallpox ended 50 years ago in the United States. That’s when the disease was wiped out in this country.

“You can’t just walk into your primary care doctor’s office or neighborhood pharmacy and ask for a smallpox vaccine,” says Dr. de St. Maurice. “It’s only available through the Strategic National Stockpile (SNS) in coordination with the Department of Public Health.” (The SNS is the nation’s reserve of vaccines, medications and critical medical supplies.)

Contact tracing is being done to identify people who have come into close contact with someone diagnosed with monkeypox. If you have been exposed, a public health worker may reach out to notify you. They can advise you on what to do next and how to access the smallpox vaccine. If you find out about being exposed from the sick person, contact your health care provider or local health department for guidance.

Timing of post-exposure vaccination

The Centers for Disease Control and Prevention recommends that the smallpox vaccine be given:

  • Within four days of exposure to monkeypox to help prevent the onset of the disease
  • Between four and 14 days after exposure to reduce the severity of symptoms, although it may not prevent the disease

Treatment for confirmed monkeypox

Most people who have been diagnosed in the current outbreak have mild symptoms and have not required specific treatment for monkeypox. However, antiviral treatments are available for those who go on to develop severe symptoms or individuals who have other conditions that may put them at increased risk of severe disease. As with the vaccine, these antivirals are administered in coordination with public health experts.

“Monkeypox can be serious,” says Dr. de St. Maurice. “But most people do well and don’t have complications.”

Learn more about monkeypox.


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