Since May, about 54,400 cases of monkeypox have been reported in 93 countries where the virus does not normally spread. More than 20,700 cases have been identified in the US alone. Many of these cases have surfaced in men who have sex with men, but anyone, regardless of their sexual orientation or behavior, can become infected and spread monkey poxwhich is primarily transmitted through close physical contact, including sexual and non-sexual contact.
In recent weeks there have been indications that the rate of transmission within homes and through other non-sexual modes of transmission, such as in the workplace, could be increasing, according to a September 1 technical report Centers for Disease Control and Prevention (opens in new tab) (CDC). Officials remain concerned that the virus can spread widely on social networks beyond men who have sex with men and into community settings such as daycares, schools, colleges and prisons.
Finally, given the likelihood of monkeypox spreading further to other environments, is everyone advised to get a monkeypox vaccine? And if officials expand vaccine eligibility criteria, would there even be enough vaccines?
Experts told Live Science that it’s unlikely everyone will be urged to get a monkeypox vaccine anytime soon, especially given the shortage of vaccine supplies. That won’t change unless the virus spreads to places like daycares, schools, or universities.
Related: First suspected case of human-to-dog transmission of monkeypox reported in France
“At this point, it’s definitely wait and see,” Rachel Roper, a professor of microbiology and immunology at East Carolina University’s Brody School of Medicine, told Live Science. Depending on how the virus spreads in the coming weeks, Roper said officials may try to expand vaccine supplies to more populations, but it’s unclear what scale of spread would prompt such a move.
“If we get a bunch of outbreaks in day care centers, that could trigger a tipping point,” she suggested.
For now that CDC (opens in new tab) recommends monkeypox vaccination for close contacts and recent sexual partners of people with confirmed monkeypox infection. Because if someone has been exposed to the virus and receives a vaccine within the next few days, vaccination can reduce the severity of symptoms or prevent the disease altogether. It is believed that this may also reduce their chances of spreading the virus further, although this idea is mainly based on studies by smallpoxa related smallpox virus, Stat reported (opens in new tab).
The CDC also recommends that men, transgender people, and people of opposite sexes who have sex with men consider a vaccine, particularly if they have recently had group sex or sex with multiple partners, or have had sex at an event or venue or in one had area where monkeypox is transmitted.
Based on the currently available data — although that data is likely incomplete — these populations still appear to be at the highest risk of infection, said Dr. Ellen Carlin, assistant research professor at Georgetown University’s Center for Global Health Science and Security, told Live Science.
Therefore, for now, the focus should be on fully vaccinating these groups against monkeypox while also collecting data to determine if booster doses may be needed, said Michael Osterholm, epidemiologist and director of the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota. “That’s going to have a huge impact on how much spillover occurs,” he told Live Science.
However, “right now, there isn’t even enough vaccine for this population,” Carlin said.
Two vaccines called JYNNEOS and ACAM2000 are used in the US to prevent monkeypox, but ACAM2000 is not recommended for widespread use. That’s because the single-dose vaccine originally developed to prevent smallpox carries a risk of serious side effects for certain groups, including pregnant and debilitated people immune systemsHeart diseases or skin diseases such as eczema, psoriasis or dermatitis, among others according to CDC (opens in new tab). These side effects include inflammation and swelling of the heart (myocarditis) and surrounding tissues (pericarditis), and the risk is high enough that the CDC determines that ACAM2000 should not be given to the above groups.
ACAM2000 may also pose risks to close contacts of a vaccinated person if those contacts fall into any of the high-risk groups listed above. The vaccine contains live vaccinia virus — a relative of the viruses that cause smallpox and monkeypox — and is given through skin punctures in the upper arm, creating an open wound, or “take,” at the vaccination site.
“The problem is that live virus can actually spread from that wound to other people,” Carlin said, so vaccinated people need to isolate themselves from those at risk while they heal. This is not a problem with the JYNNEOS vaccine, the main vaccine used in the current outbreak.
However, one problem with JYNNEOS is that there isn’t much to do.
The US held a small number of JYNNEOS doses in its strategic national stockpile early in the outbreak, but officials soon had to order more, according to the US Department of Health and Human Services (opens in new tab) (HHS). And until recently, the vaccine could only be manufactured and packaged by Denmark-based company Bavarian Nordic, which is said to be able to produce 30 to 40 million doses a year, a spokesman said NPR (opens in new tab). Using the standard two-dose regimen given 28 days apart, this supply could cover about 15 to 20 million people. But it takes time to manufacture and deliver all those doses, and it’s uncertain whether the outbreak will spread to more social networks in the lag time.
Related: Monkeypox can present with unusual symptoms, CDC warns
On that front, “I think it’s still possible to contain it — that’s my guess,” Roper told Live Science. “However, I am concerned that there may be many more cases that we are not aware of,” she noted.
Carlin agreed that the true number of monkeypox cases in the US is likely higher than reported, but she is less confident that the outbreak can be stopped before it spreads to more social networks. “I’m not optimistic that we can wipe it out,” she said. “I would be happy if the opposite were proven to me.”
To stop the spread, HHS (opens in new tab) recently struck an agreement to fill and package JYNNEOS in the United States – a move that could help the country’s vaccine supply ramp up more quickly. In addition, the US Food and Drug Administration (opens in new tab) recently expanded its guidance on vaccine administration to cover more people with available care. A full dose of the vaccine is usually injected into the layer of fat under the skin (subcutaneously). With the right needles and training, healthcare providers can now instead inject the vaccine into the outer layers of the skin (intradermally) and at one-fifth the standard dose.
Most vaccines are injected subcutaneously or into the muscle (intramuscularly), while only rabies vaccine and Bacillus Calmette-Guérin vaccine for tuberculosis are regularly administered intradermally, according to the World Health Organization (opens in new tab). However, scientists have conducted promising studies of additional vaccines, including those against flu and hepatitis B, suggesting these shots could also be administered intradermally. The appeal of intradermal delivery is that the skin is rich in immune cells that respond “really effectively” to vaccines, so this vaccine route can often elicit strong immune responses at lower doses than subcutaneous injections, Carlin said.
A small 2015 study published in the journal vaccination (opens in new tab) indicated that this could also be the case for JYNNEOS, but there is still uncertainty as to whether the adjusted dosing strategy will play out in the current outbreak, Stat reported (opens in new tab).
Should the need arise, Carlin said she wonders if federal health officials would clear ACAM2000 for widespread use, despite the potential health risks. According to HHS, as of July 1, there were more than 100 million ACAM2000 doses in the US Strategic National Stockpile. (Though smallpox has been eradicated, the nation has maintained a stockpile of vaccine if the virus was ever used as a bioterrorist weapon.)
While many groups are advised not to take the vaccine, others would be fine, Carlin said. Nevertheless, she remains “skeptical” about the introduction of the vaccine in the current outbreak.
“I would strongly advise against it,” said Osterholm of the widespread use of ACAM2000. When vaccination was used to prevent smallpox, the potential risks of the disease outweighed the risks of administering ACAM2000, but that’s not necessarily the case for monkeypox, which is usually a mild disease, he said.
It is important to note that while JYNNEOS is approved for use in adults 18 years and older, the vaccine may be offered to children through a special extended use protocol CDC (opens in new tab). The vaccine was given to some children, including infants, during a previous outbreak in the UK, and it has been given to some children in the US during the current outbreak “so far with no adverse events”. ACAM2000 can also be used in children as young as 1 year old under a similar extended application protocol.
Children under the age of 8 are at greater risk of developing severe monkeypox infections than the general public, so it would be of particular concern if the virus were to spread through this age group, Roper said. For now, however, the data doesn’t suggest that’s happening, and “for now, I just don’t think we have enough signals from the data to justify any specific expansion of vaccine eligibility criteria,” Carlin said.
As Roper suspected, we’ll just have to wait and see what happens.
Originally published on Live Science.
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