Context: With the WHO declaring monkeypox as a Public Health Emergency of International Concern (PHEIC) and cases rising globally to around 19,179 in 78 countries as of July 27, governments around the world are initiating steps towards developing or even sourcing a vaccine against monkeypox.
Are there vaccines for monkeypox?
The monkeypox virus belongs to a family of viruses called orthopoxviruses, which is different from that of the coronaviruses.
According to the WHO, it is a viral zoonosis — a virus transmitted to humans from animals — with symptoms similar, but less severe to smallpox.
It is also an enveloped double-stranded DNA virus, unlike the RNA virus, that makes it far more stable and less prone to rapid mutations.
There are two distinct genetic clades of the monkeypox virus: the central African (Congo Basin) clade and the West African clade.
The Congo Basin clade has historically caused more severe disease and was thought to be more transmissible.
Vaccine
There is yet no dedicated monkeypox vaccine
In 2019, the USFDA, approved the JYNNEOS vaccine for the prevention of smallpox, monkeypox and other diseases caused by orthopoxviruses, including vaccinia virus.
How does JYNNEOS work?
JYNNEOS, developed by Danish biotechnology company, Bavarian Nordic, contains a live vaccinia virus that does not replicate efficiently in human cells.
The vaccinia virus is the smallpox virus but made incapable of replicating within the body. It is administered as two injections 28 days apart. The immune response takes 14 days after the second dose.
The vaccine’s effectiveness was inferred only indirectly by comparing the immunogenicity of JYNNEOS to a licensed smallpox vaccine (ACAM2000) based on a laboratory test called the Plaque Reduction Neutralisation Test (PRNT).
This test evaluates what quantity of the vaccine was needed to kill the virus made to replicate in a petri-dish.
There is no data yet on JYNNEOS’ effectiveness. This is because smallpox has been eradicated and the monkeypox outbreak has risen too rapidly for a traditional phase 3 trial to have evaluated the vaccine’s effectiveness.
What about India?
Health Ministry officials said discussions were in progress with international and local companies for a vaccine.
The genomic sequence of the Indian strain has a 85% match with the West African strain circulating globally.
The ICMR has invited tenders from local companies to develop a vaccine.
Orthopoxvirus
Orthopoxvirus is a genus of viruses in the family Poxviridae and subfamily Chordopoxvirinae.
Vertebrates, including mammals and humans, and arthropods serve as natural hosts.
There are 12 species in this genus. Diseases associated with this genus include smallpox, cowpox, horsepox, camelpox, and monkeypox.
The most widely known member of the genus is Variola virus, which causes smallpox.
It was eradicated globally by 1977, through the use of Vaccinia virus as a vaccine.
The most recently described species is the Alaskapox virus, first isolated in 2015.
