CE / CME
Nurses: 1.00 Nursing contact hour
Pharmacists: 1.00 contact hour (0.1 CEUs)
Physicians: maximum of 1.00 AMA PRA Category 1 Credit™
Released: July 17, 2024
Expiration: July 16, 2025
Available Vaccines
Carlos del Rio, MD, FIDSA:
Now that we have described key aspects of the current mpox outbreak and the burden of disease, let’s focus on what we can do to prevent further infections. The first and most obvious step is vaccination.
It is presumed that when smallpox vaccination was routine worldwide, mpox outbreaks did not occur because the vaccine provided approximately 85% protection against mpox owing to the high level of sequence homology between surface proteins of MPXV and vaccinia virus. With smallpox vaccination ending decades ago (1972 in the United States), most of the population in 2022 was unvaccinated, including all individuals younger than 40 to 50 years of age, and therefore had no protection against mpox.
Aniruddha Hazra, MD:
Fortunately, we have 2 vaccines available to provide considerable protection against mpox: a smallpox vaccine and a Modified vaccinia Ankara (MVA) vaccine.
For many decades, the only smallpox vaccines available included live-attenuated vaccinia viruses that retained replication competency in human cells. Only one such vaccine remains currently available: a second-generation vaccine. This vaccine is associated with a relatively high rate of adverse effects and is contraindicated in people with severe immunodeficiency who are not expected to benefit. It is generally used for protection against occupational mpox exposure only.
More recently, a third-generation smallpox vaccine has become available that is based on a live, attenuated orthopoxvirus, MVA, that does not replicate efficiently in human cells. The MVA-BN vaccine is licensed to prevent smallpox and mpox and has shown 86% real-world efficacy against mpox following 2 doses. That is why we typically refer to the MVA-BN vaccine as the mpox vaccine.
Mpox Vaccine
Carlos del Rio, MD, FIDSA:
In order to achieve the greater than 80% protection efficacy, both MVA-BN doses should be administered 4 weeks apart. Although some protection is conferred with a single dose, it is lower than with 2 doses.
Another important educational component for patients is that the vaccine does not provide immediate protection—immunity is conferred approximately 2 weeks following the second dose in the series. Sometimes I see patients coming in for vaccination who are planning to travel or attend an event in the next day or so that may result in mpox exposure. In those cases, I explain that an adequate response to the vaccine takes 2 weeks after that second dose, which is 6 weeks after starting the mpox vaccine series.
Click for audio from Aniruddha Hazra, MD.
Carlos del Rio, MD, FIDSA:
The MVA-BN vaccine is generally well tolerated, particularly when administered via the standard route of subcutaneous injection. Most people will experience some redness and itching at the site of vaccination, and some may develop a fever, but in general, it is well tolerated with few adverse effects.
Aniruddha Hazra, MD:
I agree. People may have injection-site reactions, as they would with any other vaccine, that can be managed conservatively at home.
Mpox Vaccine: Intradermal vs Subcutaneous Injection
Carlos del Rio, MD, FIDSA:
The standard route of administration for the mpox vaccine is subcutaneous, and this is what we recommend for most patients, especially if the vaccine is widely available.
However, earlier in the outbreak, in August 2022, when vaccine was in short supply, the US Food and Drug Administration issued an Expanded Use Authorization that permitted the vaccine to be administered intradermally with a 0.1 mL volume between the layers of the skin, preferably on the inner aspect of the forearm, as an alternative to the standard 0.5 mL subcutaneous administration route under the skin in the upper arm above the elbow. This alternative regimen was authorized for use in individuals 18 years of age or older. The purpose of this authorization was to make more doses available at a time when the vaccine supply was limited, to enable more people to be vaccinated.
Clinical study data demonstrated that both administration routes have comparable efficacy.
Click for audio from Aniruddha Hazra, MD.
Summary of Mpox Vaccine Dosing Regimens by Age
Carlos del Rio, MD, FIDSA:
The MVA-BN mpox vaccine dosing recommendations from the US Centers for Disease Control and Prevention (CDC) are summarized on this slide. Subcutaneous dosing is approved for adults and for individuals younger than 18 years of age. The alternative intradermal dosing is only recommended for adults.
Coadministration With Other Vaccines
Carlos del Rio, MD, FIDSA:
One concern that came up, as mpox vaccination ramp-up occurred at the same time as waves of COVID-19 vaccination were still relatively frequent, is whether both vaccines could be administered at the same time. What are the recommendations regarding coadministration of the mpox vaccine with other vaccines?
Aniruddha Hazra, MD:
The ACIP recommends that the MVA-BN vaccine can be given without regard to the timing of most other vaccines, including simultaneous administration. That is the approach we have taken in our practice. For people who are eligible for other preventative vaccines, such as the hepatitis B virus vaccine, we are providing those at the same time as the MVA-BN vaccine.
Carlos del Rio, MD, FIDSA:
We are taking the same approach. The ACIP notes that in adolescent or young adult males, you can consider spacing out the MVA-BN and COVID-19 vaccines by 4 weeks, but at the end of the day, it really needs to be what the patient wants. The recommendations also note that if someone is at increased risk for mpox or severe COVID-19, there should be no delay in administering the vaccines.
Aniruddha Hazra, MD:
Yes, and oftentimes there is a small window of opportunity to act in that exam room. If someone is in front of me who is ready and willing to get vaccinated, I try to do as much as I can to help them feel comfortable with receiving the vaccines that would be beneficial to them.
Mpox Vaccine: ACIP Recommendations
Click for audio from Aniruddha Hazra, MD.
Carlos del Rio, MD, FIDSA:
The ACIP recommendations describe specific groups for whom the 2-dose MVA-BN vaccine series is recommended, including a group that has previously been recommended for smallpox vaccination, namely people at risk for occupational exposure, for example individuals in the military who may encounter smallpox or mpox through biological warfare.
Aniruddha Hazra, MD:
More important, what has changed since 2022 is the addition of adult populations identified as particularly vulnerable to mpox in the current outbreak, including gay, bisexual, and other men who have sex with men, as well as transgender and nonbinary people who have had in the previous 6 months or anticipate having any of a series of risk factors. The risk factors include diagnosis of an STI, more than 1 sexual partner, sex at a commercial sex venue, or sex in association with a large public event in a region where mpox transmission is occurring. The recommendations also include sex partners of anyone who meets the outlined risk criteria.
The vaccine recommendations make a point of including not only people who already meet any of these criteria but also anyone who anticipates that any of these criteria may apply to them at some point in the future, to protect against future exposures.
Carlos del Rio, MD, FIDSA:
The ACIP recommendations further note that only the MVA-BN vaccine should be used for pre-exposure protection against nonoccupational exposure. The second-generation live, attenuated vaccine—the smallpox vaccine, which retains replication competency in human cells—is only recommended for protection against occupational exposure.
Who Should Be Vaccinated Against Mpox?
Aniruddha Hazra, MD:
The graphic on this slide summarizes the current recommendations for mpox vaccination for nonoccupational exposure and highlights a critical message that we also apply to HIV PrEP: asking for this type of protection is enough to receive it, regardless of documented eligibility per the recommendations. Therefore, no additional approval is required if someone asks for the vaccine, particularly now that we have adequate supply of it.
Carlos del Rio, MD, FIDSA:
Absolutely. We also want to emphasize to people living with HIV in our care that it is important to take care of their HIV because response to the mpox vaccine will be better with higher CD4+ cell counts and suppressed HIV viral load. Discussing mpox vaccination is also an opportunity to reengage people with HIV who are not engaged in care and to talk about the importance of protecting themselves.
Aniruddha Hazra, MD:
Yes, and HCPs can recognize that people who are vulnerable to mpox are also vulnerable to HIV. Therefore, screening for HIV and potentially linking people to biomedical interventions for HIV prevention, like PrEP, should all be rolled into the discussion. Having this type of syndemic response is really important because we know that mpox, HIV, and STIs do not occur in silos, they are intimately intertwined epidemics.
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