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In USAtwo are administered vaccines (JYNNEOS and ACAM2000) to prevent monkey pox.
These vaccines are not specifically directed against this disease, but since they are used for a very similar Orthopoxvirus, such as smallpox, the Federal Food and Drug Administration The FDA recommends its use to prevent monkeypox.
Health authorities advise those who have been in close contact with confirmed cases to be vaccinated.
Monkeypox is a viral zoonotic disease – that is, it can be transmitted between animals and from animals to humans – that usually occurs mainly in tropical forest areas of central and western Africa and is sporadically exported to other regions. In May 2022, several countries reported some cases and, in July, the World Health Organization (WHO) declared this outbreak a public health emergency of international concern. In this Factchecked note We have told you what the forms of contagion are, which have made it become a concern.
And what do we know about monkeypox vaccines in the United States, for whom are they recommended, and what do we know about their effectiveness?
What vaccines are given against monkeypox in the United States?
To prevent monkeypox in those over 18 years of age, the FDA approved a vaccine in 2019. It is JYNNEOS, also known as Imvamune or Imvanex, and manufactured by the Bavarian Nordic company. This vaccine is given as two subcutaneous (under the skin) injections, preferably in the upper arm, four weeks apart.
Although Centers for Disease Control and Prevention (CDC) indicate that there is currently a limited supply of JYNNEOS in this country, “more doses are expected in the coming weeks and months.”
In addition to JYNNEOS, there is another vaccine, called ACAM2000 and manufactured by the North American pharmaceutical company Emergent Biosolutions, against this disease. In addition to being approved by the FDA to prevent smallpox, it can be used against monkeypox under an expanded access to investigational new drugs (EA-IND) protocol, which requires informed consent and additional forms.
In this case, the vaccine consists of a single dose (preferably administered in the upper arm), but requires the skin to be punctured several times with a double-pronged needle.
Although there is a greater supply of ACAM2000 than JYNNEOS, there are patients for whom the first vaccine is not recommended, the CDC says. This is the case of people with a weakened immune system; with skin conditions, such as eczema; or that they are pregnant.
In recent months, all kinds of misinformation about these vaccines have been circulating on different social networks. Among other examples that we already explained in Chequeado and in cursed.es –both media co-founders of Factchequeado–, it is not true that Pfizer have a monkeypox vaccine. False claims have also been circulated about Emergent Biosolutions’ vaccine against this disease.
Who are these vaccines recommended for in the United States?
WHO currently considers that mass vaccination against monkeypox is not necessary. “Decisions about the use of smallpox or monkeypox vaccines should be based on a full risk-benefit assessment on a case-by-case basis,” the agency states.
On the one hand, the CDC’s Advisory Committee on Immunization Practices (ACIP) recommends that people who may be exposed to Orthopoxviruses, such as the one that causes monkeypox, be vaccinated. This is known as pre-exposure prophylaxis (prevention before coming into contact with the disease).
On the other hand, both the FDA and the CDC advise vaccination when there is suspected or confirmed contact with a case of monkeypox (post-exposure prophylaxis). “The sooner an exposed person is vaccinated, the better,” says the CDC.
This agency recommends that the vaccine be administered within 4 days after the date of exposure to prevent the onset of the disease. If given 4 to 14 days after that time, the vaccination may reduce disease symptoms, but “may not prevent it.”
CDC recommends that JYNNEOS be given to certain groups of people with potentially serious immune system problems. On the web, they explain this preference because ACAM2000 “has the potential to cause more side effects and adverse events than the newer vaccine, JYNNEOS”, so that potential complications can be prevented in people with the Human immunodeficiency virus (HIV) or immunosuppressed. For this reason and to clarify any doubts, it is advisable to consult the doctor about the vaccine that is going to be inoculated.
How effective have monkeypox vaccines been shown?
There is no data yet on the effectiveness of these vaccines in the current monkeypox outbreak and it is not known what level of antibodies is needed to prevent infection, the CDC stresses. Pharmaceuticals are collecting data from observational studies that are already being done during the current monkeypox outbreak.
Keep in mind that the JYNNEOS vaccine was approved after the eradication of smallpox in 1980. This is important because The efficacy that this vaccine has shown has been seen in the production of antibodies that a person generates to protect themselves from smallpox, but there are no data on its effectiveness (in the real world), since this pathogen has been eradicated.
The efficacy of this vaccine has been studied in 2,000 adults in five different studies and trials, including patients with HIV and atopic dermatitis. Two of these investigations confirmed the ability of JYNNEOS as a booster dose in patients who had already been vaccinated against smallpox. Another study found that participants who received this vaccine had a level of smallpox antibodies similar to those who received it at the time (before 1980).
In animal studies, primates vaccinated with JYNNEOS have been shown to have an immune response similar and comparable to that of those vaccinated against smallpox. At the time, it was seen that they were protected from diseases related to monkeypox when exposed to a lethal dose (dose necessary to cause death) of this pathogen and presented much lower morbidity and mortality than animals that did not receive this vaccine. In rodents, vaccination with Imvanex has been shown to protect against lethal doses of Vaccinia virus.
There are also some human clinical trials and animal studies looking at the efficacy of ACAM2000 against monkeypox. Although there are no data on this specific outbreak, the CDC stresses that there is scientific evidence that the precursor to this vaccine was effective in eradicating smallpox.
In this Maldita.es article explains why smallpox vaccines work against other Orthopoxviruses, such as monkeypox. In fact, the WHO states that the efficacy of smallpox vaccination in preventing monkeypox is around 85%.
The immune response to JYNNEOS peaks 14 days after the second dose, according to the CDC. In the case of ACAM2000, this occurs four weeks after vaccination.
People who get vaccinated should continue to take steps to protect themselves from infection. It is advisable, for example, that they avoid close skin-to-skin contact with someone who has the disease. As we explained to you in this Factchecked note, monkeypox is not spread solely through sexual contact.
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