In a paper recently published in the International Journal of Infectious Diseases , scientists described the importance of smallpox vaccination as a preventative measure to control recent outbreaks of monkeypox infection.
Background
Monkeypox is a rare zoonotic virus that jumps from animals to humans and can also spread between humans. The virus is usually endemic in central and western Africa. However, a considerable number of monkeypox cases have recently been reported to the World Health Organization (WHO) in 42 countries around the world.
Most of these cases have been detected in the WHO European region. Notably, few of these cases have a travel history to endemic African countries. This indicates that the virus is now capable of infecting people through community transmission .
People vaccinated against the smallpox virus are less susceptible to contracting monkeypox.
However, since smallpox was eradicated in 1980, young people under the age of 40 are unlikely to have been vaccinated against smallpox.
Monkeypox outbreaks occurring in Central Africa, West Africa, and outside African countries have been proposed to be designated as clade 1, clade 2, and clade 3, respectively. Considering recent outbreaks, the virus has been found to spread efficiently among very sexually active young men who have no pre-existing immunity. Homosexual men are particularly susceptible to monkeypox infection.
In recent outbreaks, a high prevalence of human immunodeficiency virus (HIV) infection has been observed in a considerable proportion of people who have contracted monkeypox. This observation highlights the need for strict surveillance of emerging monkeypox cases to monitor the rise trajectories of recent outbreaks.
Preventive measures against monkeypox
Regarding pre-exposure preventive measures, antiretroviral treatments have demonstrated high efficacy in reducing monkeypox transmission by 50% under real-world conditions. Vaccination against the now eradicated smallpox virus has also provided 85% cross - protection against monkeypox infection.
As a pre-exposure preventive measure , vaccination is especially recommended for at-risk healthcare workers and laboratory personnel who handle clinical specimens for the diagnosis of monkeypox or work with orthopoxviruses (monkeypox, cowpox, and variola). ).
According to recent WHO guidelines, smallpox vaccines should not be widely used to control monkeypox infection. However, they recommend administering smallpox vaccines as a post-exposure preventative measure to high-risk contacts of cases within four hours of exposure.
However, given the lack of supply, vaccine prioritization is greatly needed to protect high-risk people, including gay men. Pre-exposure vaccination of high-risk homosexual men is expected to reduce monkeypox transmission in the general population.
According to a statement published by the UK Health Security Agency on June 21, 2022, "some gay and bisexual men at increased risk of exposure to monkeypox should be offered vaccines to help control the recent outbreak of the disease." virus" and that "an individual’s eligibility would depend on several factors, but would be similar to the criteria used to evaluate individuals eligible for HIV pre-exposure prophylaxis, but would apply regardless of HIV status."
Safety profile of smallpox vaccines
The first-generation smallpox vaccines developed in 1970 for the eradication program are no longer available. Subsequently, second and third generation vaccines have been developed, given the possible threat of using the smallpox virus as a biological weapon. These vaccines with improved safety profiles are now available worldwide.
The US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) approved one of these recent vaccines, namely JYNNEOS, for immunization against monkeypox virus.
JYNNEOS is a live vaccine developed from an attenuated, non-replicating orthopoxvirus , manufactured by Bavarian Nordic, Hellerup , Denmark. As a non-replicating vaccine, it can be used to immunize people 18 years of age or older who have compromised immunity due to HIV infection, atopic dermatitis, or other health conditions.
To make it available in European Union member states, the European Health Emergency Preparedness and Response Authority (HERA) has ordered 110,000 doses of the JYNNEOS vaccine. Due to the acceptable safety profile, use of this vaccine against monkeypox virus has been recommended both pre- and post-exposure .
Vaccine prioritization at the pre-exposure level should be done with optimal strategies. It is recommended that gay men who self-identify as having multiple partners, or those already being treated for other sexually transmitted diseases, be prioritized for vaccination. According to the UK Health Security Agency, people eligible for HIV pre-exposure prevention should be prioritized for smallpox vaccination.
However, it is still unclear whether smallpox vaccines can protect against the sexually transmitted monkeypox virus. Therefore, scientists recommend that the use of smallpox vaccines as a pre-exposure protective measure against monkeypox virus should be done in the form of a randomized controlled trial with another vaccine used in the control arm.
Conclusion
Since the unusual, expanding global monkeypox outbreak has so far been limited primarily to men who have sex with men, this group should at least be offered the safer smallpox vaccine on a strictly voluntary basis as pre-infection prophylaxis . exposure (PrEP) as part of a clinical trial to document protective efficacy and monitor adverse reactions. Clinical trials are needed to report protective efficacy against sexual transmission before its use can be recommended.
The scale of PrEP could be decided by reference to the level of risk of exposure in each respective jurisdiction. This will facilitate a controlled vaccine rollout and should be implemented when vaccine production has been ramped up to meet demand. Vaccine production must undoubtedly be increased to ensure access and equity also outside Europe and North America.
If vaccination can reduce sexual transmission of MPXV, it will limit the outbreak and would be an important tool to prevent further spread within and beyond the initial high-risk population.
Reference:
Petersen, E. et al. (2022) "Vaccination for the prevention of monkeypox in people with high-risk sexual behavior to control the ongoing outbreak of monkeypox virus clade 3", International Journal of Infectious Diseases . doi: 10.1016/j.ijid.2022.06.047. ttps://www.sciencedirect.com/science/article/pii/S1201971222003782
