The bovine version of smallpox, vaccinia, gave its name to vaccination. But the strain used for eradicating would in fact come from the horse.
For centuries, the infection has terrorized crowds. Leaving heavy scars, when she didn’t kill. Vaccination owes its name to smallpox, which has now disappeared. But after more than 200 years, the myth collapses. It is not the vaccine, bovine version of the disease, which made it possible to eradicate the virus.
According to a medical and historical investigation, carried out in part by the Robert-Koch Institute in Berlin (Germany), the strain used in vaccines actually comes from … the horse. A surprising conclusion explained by the researchers in the New England Journal of Medicine.
The shadow of a doubt
At the origin of this mystery, a story that every passionate about medicine knows inside out. Edward Jenner, British doctor, seeks a treatment against smallpox which then kills millions. We are in 1798.
The English scientist then found an innovative solution. He takes a sample from the arm of a milker infected with the vaccine, which affects his cows. Then he inoculates the virus to an 8-year-old child. He will never develop any sign of smallpox. The vaccine is invented.
Source : Pan American Health Organization
The anecdote could end there. But in the 1930s, a fellow Jenner noticed a disturbing detail. The strain used in vaccines, produced on a large scale, does not quite correspond to vaccinia (cowpox virus). Analysis of chicken eggs – used for production – reveals the presence of another virus. Unknown to the battalion.
The horse involved
Smallpox vaccines contain a strain whose host is not known. And no sample analyzed since confirms the presence of the vaccine. The mysterious strain is therefore renamed, vaccinia virus. And the investigation begins. Theories have multiplied. The latest seems to be the most advanced: several strains have been used depending on the context.
Researchers at the Robert-Koch Institute relied on a vaccine held by a private collector. The precious flask dates from 1902; it was produced by HK Mulford Co. of Philadelphia (USA) – which later became Merck.
Source : Jose Esparza
The analysis leaves no doubt: it is horse pox (horsepox virus) which was used as the basis for the manufacture of this vaccine. “We now have, for the first time, scientific proof that the horsepox virus has been used in the past to immunize against smallpox,” says Andreas Nitsche.
A heavy mystery
Far from being trivial, this discovery confirms the work of Clarissa Damaso, researcher at the Federal University of Rio de Janeiro (Brazil). Published last August in the Lancet Infectious Diseases, they suggest that different manufacturers used various strains, at least some of which were of equine origin.
The group is now looking for other historical samples to confirm their hypothesis. Because an unknown remains: when did we go from the vaccine to the named virus vaccinia ? A substitution has necessarily taken place.
Clarissa Damaso’s research is clear on this point: “If the vaccinia virus had been introduced randomly during vaccine production in the 18th and 19th centuries, we should find both strains, ”she explains. This is not the case. Only the vaccinia virus is present.
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