With the busyness of daily life, it’s easy to forget the viral outbreak that captivated a global audience during the summer and fall of last year. Mpox, formerly called monkeypox, may have fallen off the general public’s radar, but it has not escaped the gaze of infectious disease experts. So where are we now?
Current status
The CDC keeps close surveillance on this virus, and still provides bimonthly updates of new infections in the US. Since the beginning of the outbreak, the total number of confirmed US cases is 30,286 with 38 deaths (as of March 29). The most prevalent demographic affected continues to be men who have sex with men, although the virus has certainly not been limited to this group. Fortunately, over the past few months there has been a steep decline in case incidence. In March of this year there were an average of 0 to 2 cases documented each day, compared this to August of last year, where the average case count ranged from 200 to 400 every day.
The rise of a vaccine
An important occurrence alongside the decrease in case load was the introduction of a new vaccine. Prior to the current mpox outbreak, researchers had already dedicated efforts towards vaccines against various orthopoxviruses, including mpox, and the related virus smallpox. Thus, at the beginning of the outbreak there was hope that these vaccines could provide the immunity necessary to limit the spread of the current mpox virus outbreak. The two vaccines available at the start of the outbreak were ACAM2000 and JYNNEOS. ACAM2000 has FDA approval for the prevention of smallpox but was thought that it would also have efficacy in the prevention of mpox. JYNNEOS has FDA approval for the prevention of both smallpox and mpox. Historically, ACAM2000 had been the recommended vaccine for pre-exposure prophylaxis for those at risk of occupational exposure to an orthopoxvirus. This vaccine, a live, replication-competent vaccine, has several contraindications making it difficult to roll out to the general population. JYNNEOS, on the otherhand is a live-attenuated vaccine, in other words, a vaccine containing a weakened virus that cannot replicate efficiently. The US Food and Drug Administration had approved the vaccine in 2019, and although it was initially designed to be injected subcutaneously (beneath the top skin layer), in August 2022 the FDA authorized it to be injected intradermally (between skin layers). Administration of the vaccine intradermally allowed for a smaller dose to be used resulting in more individuals being vaccinated with the limited number of doses available. The US has distributed over 1.2 million doses of the JYNNEOS vaccine. Preliminary analysis of mpox cases since implementation of the vaccination effort have found approximately 10 cases among unvaccinated cases for every 1 fully vaccinated case.
Moving forward
Although case numbers are declining and the virus is receiving less coverage on the news, this outbreak is not over. New infections continue to be reported, and there remains much to be learned about the transmission patterns of the mpox virus: Is its spread limited to physical contact? Could it ever become airborne? We also don’t know how long immunity to mpox will last following administration of the JYNNEOS vaccine. Additionally, in the era where global travel is accessible to virtually everyone, this virus–originally endemic to specific regions until it transformed to a multi-country outbreak–serves as a sobering reminder of how quickly a pathogen can become a global problem. Thus, even as this outbreak has threatened to fall from the general public’s interest, it continues to deserve our attention, so we see what else scientists discover about this virus, and how they implement this new knowledge in the face of future epidemics.
Follow bimonthly updates by the CDC here: https://www.cdc.gov/poxvirus/mpox/response/2022/index.html
Taylor is a medical student at the University of Texas Medical Branch in Galveston. She is hoping to pursue her interest in infectious diseases by specializing in Internal Medicine or Pathology.
Sources:
Centers for Disease Control and Prevention (2023). Mpox: 2022 Outbreak Cases and Data. US Department of Health and Human Services.
National Institute of Allergies and Infectious Disease (2023). Mpox (Formerly Monkeypox) Vaccines. USA.gov.