Listen to Story The new monkeypox (or mpox) outbreak has already reached other continents after having been seen in the Democratic Republic of the Congo in the African continent. It surfaced in 2022, but this time the strain of the virus is different from the previous one. This strain has recently jumped from animal to man and is called Clade 1b.
The last strain, Clade 1, had settled down in 10 months. The WHO has sounded an alarm calling the mpox outbreak a public health emergency of international concern. The mpox virus is also known as a cousin of the smallpox virus.
And because they are related in some ways, it is being said that the smallpox vaccine can provide some protection against the mpox virus too. While smallpox was officially eradicated in the US in 1972, it was eradicated in India in 1979. Since then, mpox is being seen more in unvaccinated people.
Dr Rajeev Jayadevan, infectious diseases expert and member of IMA Kochi said, “There is no vaccine created specifically for the mpox virus. When the global mpox outbreak occurred in 2022, we were hoping that the smallpox vaccine could cross-protect against mpox." Both mpox and smallpox are related to the vaccinia virus.
The existing smallpox vaccine is created based on the vaccinia virus. So, imagine there are Virus A, Virus B and Virus C. They have created a vaccine on the basis of the Virus C with an aim to protect against A and B.
In other words, a vaccine that offers cross protection against smallpox also gives cross protection against monkeypox. Data from western nations since the 2022 outbreak suggests that among those who took the modern version of the smallpox vaccine (Jynneos), there was substantial reduction in the number of mpox cases. Now let’s look at the case of someone who had a smallpox vaccination in childhood.
They would now be 45 years or older going by the years in which the smallpox vaccination stopped. These people theoretically could still have some protection, but on ground data did not fully support this theory. There have been cases of several people with prior vaccination of smallpox getting infected with mpox.
Perhaps the vaccine derived immunity waned after all these years. We can say it could offer some cross protection, but it’s not foolproof protection. “Chicken pox has no similarity with mpox except for the fact that the skin lesions look the same.
In fact, one can be confused with the other. If someone has chickenpox vaccination or infection, it offers no cross protection against mpox because they are entirely different and unrelated viruses,” said Dr Jayadevan. “Regarding the vaccines for mpox, smallpox vaccines do provide significant protection due to the close genetic relationship between the two viruses.
Two vaccines are currently used. The smallpox vaccine (vaccinia virus vaccine) has been shown to offer cross-protection against mpox due to the genetic similarities between the two viruses. This vaccine was originally developed to eradicate smallpox, and since the two viruses belong to the same family, the immunity provided by the smallpox vaccine can indeed reduce the severity of mpox or prevent it altogether,” said Dr Giridhar Babu, epidemiologist, physician scientist, author on global health and infectious diseases.
He added, “However, the chickenpox vaccine, which is designed to protect against the varicella-zoster virus, is not related to mpox and therefore does not provide cross-protection. The varicella-zoster virus belongs to a completely different family of viruses (Herpesviridae) and does not confer immunity against orthopoxviruses like mpox.” On the likely impact of mpox being declared as a public health emergency of international concern, Dr Babu said, “The recent upsurge of mpox cases, particularly the spread of new variants and their impact on both adults (mainly through sexual contact) and children, highlights the urgent need for vigilance and preparedness, especially as populations return to school and other communal settings after vacations.
".
