As global health leaders investigate an unusual outbreak of monkeypox across more than a dozen countries, discussions in the United States have turned to vaccination against the disease – and certain people exposed to the virus could be offered a vaccine.
The US has mobilized vaccine for monkeypox to states that have reported cases, and officials plan to move the vaccine where it may be needed, Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention, said Thursday.
“The US has the resources we need to help us respond to monkeypox in this country right now. We’ve been preparing for this type of outbreak for decades,” she said.
The US has two preventive vaccines and two antiviral treatments that can be used for orthopox, the family of viruses that includes monkeypox.
“One of these vaccines, with the trade name of Jynneos, is approved for the prevention of monkeypox disease in adults 18 years of age and older,” Walensky said. “CDC has mechanisms in place to move these products around the country so that they can be used for prevention or treatment for people who may benefit, wherever they may be.”
CDC officials are recommending vaccination for people at highest risk of infection due to direct contact with someone who has monkeypox.
“Right now, while we are in the early phase of investigating this, we know that those at highest risk for infection are those who had contact with a known monkeypox patient, with the kind of contact that would facilitate spread. So those are the individuals we’re really focusing on recommending vaccination for right now: post-exposure vaccination,” said Dr. Jennifer McQuiston, a veterinarian and deputy director of the CDC’s Division of High Consequence Pathogens and Pathology.
“We continue to watch what is happening and think about whether wider vaccination recommendations would make sense, but at this time, we only have nine known cases, and we have contacts that we’ve identified associated with those cases that would likely most benefit from vaccines,” McQuiston said. “And so that’s where we’re focusing our energies right now.”
Vaccines for monkeypox have been made available to some health care workers treating infected people.
“I’m happy to report, even with the first case in Boston at Massachusetts General Hospital, our colleagues across the government have been able to get vaccines to that hospital. And just yesterday they’ve already started offering the vaccines to health care workers who have been exposed,” Dr. Raj Panjabi, who leads the White House’s monkeypox response, told CNN’s Laura Coates on Monday night.
“The first part is to identify those who are infected and to isolate them and make sure that they get the care they need,” Panjabi said. “The second part is to ensure we vaccinate those who’ve been exposed to the infected individuals. If we do that again and again – and that’s our approach at the White House and across the government – then we have a better chance of ending this outbreak.”
Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health, says not to expect a large-scale rollout of vaccines.
“I think that we will need to use vaccinations in contacts of cases. This isn’t something where everybody lines up and gets vaccinated,” he said of the current outbreak. “That’s going to be critical to stopping cases.”
What vaccines could work against monkeypox?
A senior Biden administration official said Tuesday that there’s sufficient vaccine to cover the United States’ current level of cases.
“Right now, we have over 1,000 doses of [Jynneos] available, and we expect that level to ramp up very quickly in the coming weeks as the company provides more doses to us,” McQuiston said Monday.
The CDC estimates that the vaccine is at least 85% effective in preventing monkeypox, based on data from Africa.
Another vaccine, called ACAM2000, is licensed in the United States to prevent smallpox. Although the vaccine could be used to prevent monkeypox, it is not licensed for that.
The United States has more than 100 million doses of ACAM2000, McQuiston said.
“ACAM2000 is an older-generation smallpox vaccine that has some potential significant side effects with it,” she said. “So a decision to use that widely would have to have some serious discussion behind it.”
ACAM2000 is a live virus vaccine – and once the shot is given, a lesion will develop at that site. Because the virus grows at the site of the lesion, it can spread to other parts of the body or even to other people, according to the CDC, which is why people who get ACAM2000 “must take precautions” to prevent the spread.
In comparison, the Jynneos vaccine is given as a live virus that is non-replicating. That means there is no visible “take” and, as a result, no risk of viral spread, according to the CDC. Some common vaccine side effects include pain at the injection site, muscle pain, headache or fatigue.
Who should get vaccinated against monkeypox?
Most people won’t be vaccinated against monkeypox.
The CDC’s Advisory Committee and Immunization Practices voted last year to recommend vaccination for select groups at risk for monkeypox and other related viruses due to their occupations, like research lab personnel and health care workers.
Amid the global outbreak, World Health Organization officials plan to make recommendations on who should be prioritized to receive a smallpox vaccination to lower their risk of monkeypox.
“We will be making recommendations on who should be prioritized for this,” Maria Van Kerkhove, WHO’s emerging diseases and zoonoses lead and technical lead on Covid-19, said during a social media Q&A Monday.
“This is not something that everybody needs. It is a virus that is spreading between people who are coming in close contact with those who are cases,” Van Kerkhove said. “We really need to discuss evidence-based use of these measures, access and equity.”
Andy Seale, strategies adviser for the WHO Department of Global HIV, Hepatitis and STI Programmes, added that vaccinations should be considered for countries where monkeypox is endemic, which are in West and Central Africa.
“Communities are already saying to us, ‘if we get this right, if we contain this, if we get the access right for the outbreak, we have to do this for the endemic countries as well,’ ” Seale said.
Can someone get vaccinated after being exposed to monkeypox?
Vaccination after exposure to monkeypox virus can still offer some protection, according to the CDC.
“That’s the norm. We usually don’t do vaccination of everybody beforehand. We use vaccination as post-exposure prophylaxis,” Adalja said.
“Because monkeypox has a long incubation period, just like smallpox – it’s 12 days or so, on average, for monkeypox – you can intervene with a vaccine in an exposed person, and it will abort the infection,” he said. “Or if you do get an infection, maybe it gets to them really late or late in the incubation period, it makes the infection less severe.”
But the sooner an exposed person gets the vaccine, the better. The CDC recommends giving the vaccine within four days of exposure in order to prevent illness. If it’s given between four and 14 days of exposure, vaccination may reduce the symptoms but may not prevent the disease itself.
Overall, people who have been exposed to the monkeypox virus and have not gotten the vaccine within the past three years should consider getting vaccinated, according to the CDC.
Will a smallpox vaccination protect against monkeypox?
“Because monkeypox virus is closely related to the virus that causes smallpox, the smallpox vaccine can protect people from getting monkeypox,” the CDC website says. “Smallpox and monkeypox vaccines are effective at protecting people against monkeypox when given before exposure to monkeypox. Experts also believe that vaccination after a monkeypox exposure may help prevent the disease or make it less severe.”
Scientists have known for years that smallpox vaccines can be effective in preventing monkeypox, too. The variola virus that causes smallpox and the monkeypox virus belong to the same family.
“The viruses come from the same family of viruses, and what we’ve seen in prior monkeypox outbreaks is that vaccinating contacts does abort infection or attenuate infection in those individuals with monkeypox,” Adalja said.
There probably is some “remnant” of protection against monkeypox for adults who were vaccinated against smallpox as children, he said, but it may not be full protection.
“The smallpox vaccination program ended in the 1970s in the United States. Obviously, if someone is in the US military and they got vaccinated last year, I’m sure they’re completely protected,” Adalja said. “But people who got vaccinated as children in the era when smallpox was a routine childhood vaccination, they may have some residual immunity.”
The senior administration official said Tuesday that, theoretically, there is some protection offered from a previous smallpox vaccination, but there is not good evidence on how much protection – and that protection could wane over time.
Has the monkeypox virus changed with this outbreak?
The official said that it doesn’t seem like anything has changed about the biology of the monkeypox virus and that the chances of contracting it are still very low for the general public.
WHO officials have not found evidence of the monkeypox virus changing or mutating in this outbreak. Therefore, there is no evidence to suggest that the licensed vaccines won’t work against the currently circulating virus.
“It’s a very stable virus. So we don’t yet have evidence that there’s mutation in the virus itself,” Rosamund Lewis, head of smallpox secretariat at WHO Emergencies Programme, said during the Q&A on Monday.
“We are beginning to collect that information,” Lewis added. “We will be convening our groups of virologists and other experts who will discuss this very question based on the sequence of the genome of some of the cases that are being detected.”
Get CNN Health's weekly newsletter
Sign up here to get The Results Are In with Dr. Sanjay Gupta every Tuesday from the CNN Health team.
That is a “key question” that is important to answer, said Dr. Daniel Rhoads, co-chair of the College of American Pathologists Microbiology Committee.
“Did something change with the biology, or is this just an unusual situation that hasn’t happened before or we haven’t recognized it before? I think anytime there’s a change in geography for these endemic diseases, that’s a key question,” said Rhoads, a pathologist at Cleveland Clinic in Ohio.
“Whenever we see a new infection or an infection transmitted in what seems to be a new way, I always wonder, is this just something we haven’t recognized before that’s always been around? Or is this an actual biological change, which would be due to a mutation in the virus? I don’t know,” Rhoads said.
“My guess is, once they sequence the virus causing the current outbreak, they’ll be able to compare it to known sequences, and then hopefully we’ll have some insight as to whether or not this is kind of the same old monkeypox or if there’s something that appears to be different.”