Cases of monkeypox (likely soon to be dubbed MPXV by the World Health Organization) are proliferating worldwide, but many experts say it seems unlikely to develop into a pandemic like COVID-19, AIDS, or SARS.
The Centers for Disease Control & Prevention (CDC) says the risk to the U.S. population is low. Nonetheless, the World Health Organization (WHO) Director-General tweeted on June 14 that he is convening a meeting June 23 to determine whether the expanding outbreak constitutes a global health emergency.
“Does monkeypox have the potential to become a pandemic of significant proportion?” Cesar Arias, MD, PhD, co-director of the Center for Infectious Disease at Houston Methodist, asks. “The answer, as with any transmissible virus, is yes, but whether that will happen is the million-dollar question. Transmission is occurring (outside the regions in which it is endemic) and the magnitude of the transmission is unknown. After what we experienced these past three years, we should be cautious.”
David Dodd, chairman, president, and CEO of GeoVax, is optimistic. “It’s an issue, but it likely won’t become a pandemic like COVID-19. There probably is an element of hysteria to it right now.” His confidence is based on a body of research into monkeypox going back at least two decades, its method of transmission, and the availability of vaccines and therapeutics to counter this virus.
Two vaccines available in United States
The CDC says the vaccines developed against smallpox also offer 85% protection against monkeypox. Currently, there are two vaccines approved for smallpox in the U.S., Jynneos™ and ACAM2000. Of them, only Jynneos is approved for monkeypox.
Bavarian Nordic’s Jynneos is a nonreplicating modified vaccinia Ankara (MVA) vaccine that is FDA-approved for both smallpox and monkeypox. The company received an order from BARDA for 500,000 liquid-frozen doses for delivery this year. Receipt of that order will increase the U.S. stockpile to 1.9 million doses. Most of Bavarian Nordisk’s remaining bulk Jynneos vaccine will be freeze-dried into approximately 13 million doses by 2025. The vaccine, known as Imvanex® in the U.K., was delivered to England in 2018 in response to a monkeypox outbreak there.
ACAM2000 is a second-generation smallpox vaccine developed by Sanofi Pasteur Biologics. This live vaccinia-based vaccine is licensed to immunize people at high risk of contracting smallpox. It is part of the U.S. Strategic National Stockpile for smallpox.
GeoVax considered monkeypox even before the outbreak. “We already have published in peer-reviewed journals that our MVA vaccines, in addition protecting animal models against HIV and other infections, also prevents monkeypox,” Dodd says. “We are validating our COVID-19 vaccine (CM04S1) now, which, is in Phase II trials, [and we] also will address the monkeypox virus.”
Likewise, “Moderna is investigating potential monkeypox vaccines at a preclinical level, using its mRNA platform,” Luke Mircea-Willats, corporate spokesperson, says.
Others are watching the situation carefully. “Inovio Pharmaceuticals produced preclinical data on a monkeypox vaccine, published in the Journal of Infectious Diseases in 2010,” corporate spokesman Jeff Richardson says. “There has been no further work on this particular vaccine since that publication.” Inovio is monitoring the outbreak of this and any other infectious disease threats, with the potential of applying its DNA medicines platform as applicable.
Mass vaccination not needed
As yet, Arias says, “I don’t see real evidence of airborne transmission. It is not associated with sexual behaviors either, but with proximity to active, infective, skin lesions.” The CDC says monkeypox is transmitted through direct contact with infectious sores, scabs, or bodily fluids from those infected. So, unless the virus becomes airborne—which the WHO says is possible but uncommon—wearing masks won’t affect transmission.
That also means wide-spread vaccination is unnecessary. The CDC recommends vaccination only for people likely to contact monkeypox, such as lab workers exposed to certain orthopoxviruses and certain military personnel.
Vaccination also is recommended after exposure. To prevent the onset of monkeypox, the vaccine must be administered within four days of exposure. When given up to 14 days after exposure, however, vaccination may ease the symptoms but not prevent disease onset.
Baby Boomers and GenXers shouldn’t assume they’re protected from monkeypox or smallpox. “It is unlikely that the first-generation vaccine for smallpox, which was administered until 1972 in the United States, will withstand a new challenge,” Arias says. “The newer vaccines seem to work [better]. The question is whether we have enough, if this gets out of hand.”
Antiviral meds ready, too
If it does spread, antiviral therapies are available. Siga Technologies’ antiviral drug, TPOXX® (tecoviromat), is approved to treat monkeypox in Europe. “TPOXX blocks the spread of virus while allowing the induction of a protective immune response,” Dennis Hruby, CSO, tells GEN. “The approved course of therapy is two oral doses per day for 14 days.” It recently received FDA approval for an intravenous version for those who cannot easily swallow pills.
Although TPOXX is not FDA-approved for use in the United States against monkeypox, it may be used under an expanded access protocol to treat monkeypox during an outbreak. It already has been used on at least one patient during the current outbreak, Hruby adds.
Vistide® (cidofovir) by Gilead Sciences, is approved for the treatment of cytomegalovirus retinitis in AIDS patients and also holds expanded access protocol authorization for monkeypox, as does vaccinia immune globulin intravenous (VIGIV).
Additionally, an expanded access—investigational new drug application (EA-IND) is being prepared for a fourth therapy, Tembexa® (brincidofovir) by Chimerix, for monkeypox. (The intention to sell Tembexa to Emergent BioSolutions was announced in early May.)
Scientists watch closely
During the COVID-19 pandemic, scientists frequently pointed out that the science was changing, while trust in public health officials waned. Going forward, Dodd says, earning the public’s trust “is less about getting the information right or wrong and more about being transparent,” and pivoting as needed. “People are much more accepting of that.” So, as long as the experts admit when they are wrong and adjust their strategies to adapt to new information, they can regain—and maintain—the public’s trust, he suggests.
While no can accurately predict what will happen regarding the monkeypox outbreak, it merits close scientific observation.
“Monkeypox is a serious infection and can be fatal,” Anne Rimoin, PhD, professor of epidemiology and director of the UCLA Center for Global and Immigrant Health, said in a Q&A blog post. She has studied monkeypox for some 20 years and says transmission patterns are changing. Specifically, it is expanding beyond the areas of Africa in which it is endemic. In fact, the current outbreak is “the largest-ever outside of Africa.”
Transmissibility and fatality depend on the clade, with the Central Africa/Congo Basin clade associated with 6% to 10% mortality and the West African clade with 1% to 3.5% mortality. Access to vaccines and therapeutics improves those risks, however. “There haven’t been any fatalities in high-income settings,” she points out. “There are vaccines and treatments, and the world is more aware of what it takes to contain outbreaks.
“The risk of monkeypox to the general public is low. It is still a rare infection…and it is unlikely that most people in the U.S. will ever come in contact with it,” Rimoin says.