The Centers for Disease Control and Prevention says the U.S. stockpile includes over 100 million doses of an older generation of smallpox vaccine believed to be effective against monkeypox, and it is aiming to accelerate the supply of a newer vaccine that could help curb a potential outbreak. Its European counterpart recommended on Monday that countries update contact-tracing systems and “review the availability of smallpox vaccines, antivirals and personal protective equipment for health professionals.”
While studies suggest that smallpox vaccine — given to some military members and lab workers — is at least 85 percent effective against monkeypox, according to the CDC, the shot is linked to rare, serious side effects such as heart inflammation, the agency says. It recommends that people with weakened immune systems or certain skin conditions should not take it unless exposed.
Still, the CDC says that for most people, the risks from monkeypox are greater than from either vaccine.
The older smallpox vaccine “has some potential significant side effects with it, so a decision to use that widely would have to have some serious discussions behind it,” Jennifer McQuiston, a CDC deputy director, told reporters in a news conference Monday after President Biden said the country was exploring vaccine options.
Any vaccine distribution now would focus on people “that we know would benefit from it,” such as health-care workers or those who came in close contact with a confirmed case, she added. Many countries, including the United States, Britain, Canada and France, stopped routine smallpox vaccinations in the 1970s, as the disease was eliminated around the world.
German authorities have warned that Europe is facing its largest outbreak of the disease, characterized by a rash and lesions that are the most significant source of spread, such as through skin-to-skin contact. In the United States, a single case was confirmed as of Monday, in Massachusetts, with four potential cases under investigation. More than 100 cases have been confirmed in at least 13 other countries outside West and Central Africa, where the disease is endemic.
The U.S. stockpile has more than 1,000 doses of the newer vaccine, Jynneos, which is not widely available and was approved in 2019 for the prevention of smallpox and monkeypox, the CDC’s McQuiston said.
“We expect that level to ramp up very quickly in the coming weeks, as the company provides more doses to us,” McQuiston said. The company that developed Jynneos has said the U.S. government exercised its option for a $119 million order that will allow for a freeze-dried version of the shot to be manufactured and invoiced in 2023 and 2024.
The European Center for Disease Prevention and Control said smallpox vaccine doses could be considered after exposure for close contacts who are at high risk, but it noted that more information is needed on their use for groups that face increased risk of severe disease.
The World Health Organization, which has a stockpile of smallpox vaccine previously estimated at 31 million doses, has noted that immunity will probably be limited to older people who were vaccinated before countries such as the United States stopped administering shots to the public.
As Britain records a rise in cases, it has offered a smallpox vaccine to some health workers. Meanwhile, Germany’s health minister said the country was evaluating vaccine options for those who may be at risk but noted that “vaccination of the general population is not being discussed.”
A senior WHO official echoed those comments on Monday. Richard Pebody, who leads the high-threat pathogen team in Europe, told Reuters the WHO believes the monkeypox outbreak does not require mass vaccination because hygiene and safe-sex measures, as well as contact tracing and isolation, can help to control it.
He said immediate vaccine supplies and antiviral treatments were limited but added that the virus does not spread easily. WHO epidemiologist Maria Van Kerkhove also described the outbreak on Monday as “a containable situation” and said stopping transmission was possible.
The so-far unexplained monkeypox spread has raised some alarm as the world reels from the coronavirus pandemic, but health officials have stressed that this virus is neither new nor as easily transmissible. The latest spate of cases stands out in part because many have no travel links to countries where monkeypox is more regularly found, according to health officials.
Annabelle Timsit contributed to this report.