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.
Vaccines for monkeypox are now 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.”
A senior Biden administration official said Tuesday that, in general, small clusters of people who have been exposed to a monkeypox patient with symptoms could be offered vaccination – but this is not a mass vaccination effort.
In the United States, the Jynneos vaccine, given as two doses four weeks apart, is licensed to prevent smallpox and monkeypox in adults.
“Because monkeypox virus is closely related to the virus that causes smallpox, the smallpox vaccine can protect people from getting monkeypox,” the US Centers for Disease Control and Prevention 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,” said Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for HealthSecurity.
But don’t 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,” Adalja said of the current outbreak. “That’s going to be critical to stopping cases.”
The senior 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,” Dr. Jennifer McQuiston, deputy director of the Division of High Consequence Pathogens and Pathology within the CDC’s National Center for Emerging and Zoonotic Infectious Diseases, 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.
Most people won’t be vaccinated against monkeypox. It’s based on direct exposure.
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. That could include research lab personnel and health care workers, for instance, who treat infected people.
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.
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.
There probably is some “remnant” of protection against monkeypox for adults who were vaccinated against smallpox as children, Adalja 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 Biden 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.
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.”
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.”