V. Vaccinia Virus, the Real Smallpox Vaccine
Several weeks ago I told you how cowpox was an important virus because Dr. Edward Jenner, the English physician, used it to vaccinate against smallpox. People inoculated with cowpox developed a localized infection of pustules, but were protected from getting the more dangerous smallpox virus later in life.
Back then, scientists didn’t have the tools to prepare large stocks of vaccines and store them. The cowpox “vaccine” was kept by passing the virus from human-to-human. If freshly infected humans weren’t available, new virus was taken from infected cows. Needless to say, the quality of the vaccine could not be controlled.
A breakthrough came in the early 1920’s when some French colonies and Indonesia developed a preparation of vaccine that could be air-dried or freeze-dried. This revolutionized growth and distribution of the vaccine.
By the 1940’s, the company, Wyeth, was the leading manufacturer of Dryvax, the current vaccine recommended for smallpox. This vaccine was developed from a weak strain of virus called the New York City Board of Health strain.
In 1967, the World Heath Organization started its global program to eradicate smallpox from the entire world. Amazingly this goal was met in 10 years due to the production and distribution of the modern vaccine. The last naturally occurring case of smallpox was in Somalia in 1977.
Today we no longer need to vaccinate for smallpox and only two laboratory sources of smallpox are kept: one in the US and one in Russia.
When modern genetic techniques were developed, scientists compared the vaccine virus to cowpox and smallpox. Although the vaccine virus is similar to both, it turns out that it is different enough to be considered a separate virus. At some point during the passing of virus from human-to-human and collection of virus from cows, a new virus emerged.
Scientists speculated that the vaccine virus is a hybrid between cowpox and smallpox, and named the new virus vaccinia virus to denote its role as a vaccine virus.
Interestingly, vaccinia virus does not occur naturally in nature, but has become a significant research tool to help scientists understand how the family of pox viruses infects and causes disease in animals.
From milkmaids to cowpox to vaccinia virus, the history of the smallpox vaccine is a complicated and intriguing story!