Unlike the virus that causes chickenpox , varicella, which belongs to the herpesvirus group of viruses, monkeypox virus belongs to a group of viruses called orthopoxviruses. These are are group of DNA viruses (viruses whose genetic material consist of DNA, rather than RNA, the kind of genetic material carried in SARS-CoV2, the virus that causes COVID-19). Orthopoxviruses include monkeypox virus as well as the notorious variola virus that causes smallpox, plus a virus called vaccinia. The latter virus causes cowpox, a viral disease that does not typically kill humans and generally produces pox lesions on the hands and wrists, while sparing the face. This is what led to the invention of vaccination in the 1790s, because milkmaids —young women who milked cows— were reputed to be very beautiful, because their faces were free of pox scars.
The English physician Edward Jenner reasoned, correctly, that exposure to cows somehow protected milkmaids from smallpox, whenever the smallpox would breakout in a new location. Up to this point, there had been a preventive treatment against smallpox called inoculation. This meant obtaining fluid from pox lesions of smallpox victims and putting the fluid into the blood of other people to give them a mild case of small pox. This actually did protect people against smallpox, because those who were inoculated mounted an immune response, but it was very risky because sometimes the cases of smallpox that they developed in the days following inoculation were not so mild. Using instead, fluid from cowpox lesions, Jenner was able to produce active immunity in people against smallpox without putting them at risk of getting any kind of case of smallpox. At the time, viruses were unknown, but the process that replaced inoculation was named vaccination, because of of the word vacca, Latin for cow. Based on that, once viruses were discovered, the virus that causes smallpox was named vaccinia. This history will be useful, a little later in the post when we discuss vaccination against monkeypox.
What’s different about this monkeypox outbreak from the earlier days of monkeypox is that it is spreading in countries where the virus was previously not known. Initially, news about the outbreaks emphasized how most of the cases occurred in homosexual men below the age of 50 or so, and this group still does represent many of the cases. However, anybody else case come down with a monkeypox infection too, including pregnant women. In pregnancy, the initial symptoms and signs of monkeypox are similar to those outside of pregnancy. This means fever, swollen lymph nodes, fatigue, sore throat, headache, muscle aches, and notably a rash with very bad lesions. The lesions are often in the anogenital area but also can be on the torso, the legs and arms, the face, and the palms and soles. Appearance of the skin lesions varies in terms of their size and the amount of crusting, but in most cases they are extremely painful.
If you have a skin lesion with an unknown origin, whether or not it is painful, you should visit your doctor and have sore evaluated. The US Center for Disease Control and Prevention (CDC) has warned doctors that sores of monkeypox can mimic lesions of other skin infections. These other infections include some that commonly infect the genital area, including some sexually transmitted infections. The other infections also include varicella zoster (chickenpox) as well as herpes, both the sexually-transmitted and the non-sexually transmitted kind. Having such viral infections diagnosed early is very important, because often there are treatments that can help, but only if given early in the course of the disease.
As of early September, 2022, data are still very limited with respect to the effects of monkeypox on pregnancy. According to the CDC, it is possible to transmit monkeypox virus to the fetus or to the newborn. The latter can happen, especially during breastfeeding. This means that if you do come down with monkeypox, pumping could be a better option than direct breastfeeding. Additionally, cases of adverse outcomes of monkeypox during pregnancy have been reported, including spontaneous abortion (early miscarriage), stillbirth (late miscarriage), and preterm delivery, but the risk of these outcomes is not known, because the number of such cases has been small.
As for vaccination against monkeypox, being caused by an orthopoxvirus, monkeypox can be prevented by the same vaccines that protect against smallpox. The latter is a disease that has been eradicated, so the most recent generation of people to have been vaccinated routinely against it are now approximately age 50. This may be related to the fact that cases of monkeypox and the worst cases are occurring in people below the age of 50. It’s possible that people who were born up to the early 1970s, the last years when babies were vaccinated against smallpox may still hold some tiny amount of immunity against, both smallpox and monkeypox compared with those who are younger and thus were never vaccinated (unless they were in the military and received smallpox vaccination against the possibility of smallpox being used as a biological weapon). On the other hand, researchers do not think that people who received smallpox vaccination as children are well protected, but simply just a little be more protected than younger people.
As for available vaccines, there are two types: JYNNEOS and ACAM2000. ACAM2000 is administered by pricking the skin a few times with two-pronged needle. This is the way that people over age 50 were vaccinated against smallpox as babies and it’s not particularly pleasant, but it works against both smallpox and monkeypox. Because this is a live vaccine —it’s the vaccinia virus that causes cowpox, a mild disease— it’s generally not recommended during pregnancy, but this recommendation against it does not hold in cases when a pregnant women is at extreme risk from monkeypox. Extremely risk could be something like a known exposure through a person with monkeypox. In contrast with COVID-19 vaccines, both of these orthopoxvirus vaccines can actually help against the disease if you’re vaccinated after exposure. If you are not at risk, however, authorities do not want you to receive ACAM2000, during pregnancy. They also warn that you should avoid being close to people who have received it, because they can spread the vaccine, which is a live virus.
In contrast, JYNNEOS also is a vaccinia virus, but it has been attenuated (weakened) to the point that it does not replicate in the person who receives it. Thus, it is being discussed more as an option for pregnant women, although, even in the case of JYNNEOS, they’re saying not to receive it, if you are not at risk. All of this can change, of course, if the spread of monkeypox becomes worse in the weeks or months to come. As for the route of administration, JYNNEOS is given as a subcutaneous injection, but unlike the ACAM2000, it’s not the double needle that gets poked multiple times. Interestingly, given the unusual way to administer ACAM2000, there has been some discussion around an idea to recruit older nurses out of retirement so that they can teach younger nurses and doctors how to perform this type of vaccination that was so common up to a half-century ago.
