History Of Yellow Fever Vaccine

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History Of Yellow Fever Vaccine

As the nineteenth century came to a close, yellow fever had already established itself as a dreaded disease in the Western hemisphere and the coastal parts of West Africa. There was no known treatment for yellow fever during that time. The only thing that doctors knew that outbreaks used to occur when ships anchored in ports, and those who recovered from the fever acquired immunity to subsequent outbreaks.

At the same time, advances were made in medicine and researchers came to know about bacteriology. So, some researchers made claims that they had manage to isolate the bacterium responsible for causing yellow fever and they also made vaccines using the isolated bacterium. This led to the appointment of Dr George Sternberg by the US president, Grover Cleveland, to check on the authenticity of these claims. Dr Sternberg found that the claims were not correct as the vaccines were completely ineffective.

After the end of the Spanish American War, yellow fever was rampant in Cuba. Even installing proper sanitation system did nothing to reduce the number of cases. This led to the appointment of a Yellow Fever Commission to examine more about the causes of the fever. Through investigations and studies, the Commission found that the disease is transmitted through mosquitoes and the agent causing the infection could be filtered through Berkefeld filter. However, the researchers could not infect animals with the agent. So, the researchers went on to immunize people using a very small dose of the agent. Out of the 42 participants, 8 became ill and subsequently died.

With the opening of the Panama Canal in the year 1912, suddenly there was a risk of vast number of people getting exposed to yellow fever. So, the International Health Commission (IHC) of Rockefeller Foundation decided to help in finding a cure for the disease.  A team from the IHC was sent to Ecuador to the city where there was an endemic earlier on to help control the disease. One of the team members was a Japanese researcher named Hideyo Noguchi who was responsible for discovering a spirochete known as Leptospira icterohemorrhagiae, which was responsible for causing Weil's disease. The researcher thought that there might be similarity between yellow fever and Weil's disease. So, Noguchi started looking for the spirochete in the patients. He found them in the liver and also found that he could transmit them to guinea pigs. Noguchi thought that he had found the agent that caused yellow fever, and he ended up naming the spirochete Leptospira icteroides. He went on to produce a vaccine as well as antiserum for the disease. This vaccine was used quite a bit in the US, Latin America and in Africa where the French had established colonies. While Noguchi made publications of his trials, no researcher could duplicate his results.

In the year 1926, another researcher named Max Theiler along with Watson Sellards proved that Leptospira icteroides found by Noguchi was identical serologically to Leptospira icterhemorrhagica. This prompted Rockefeller Foundation to stop making the vaccine. However, after the end of the First World War, the Foundation began its investigations in the disease in Africa. This led to the formation of another West African Yellow Fever Commission in the year 1925. The previous commission was established in the year 1920, but it did not accomplish too much. The Commission sent researchers to figure out whether the yellow fever there was same as the one in Latin America.

Then, in the year 1927, blood from an African who had a mild febrile illness was injected into a rhesus monkey and the monkey got infected with yellow fever. This was the first time a lab animal was infected with the fever. Noguchi came a few months later to help in the research. However, Noguchi could not prove his theory and succumbed to yellow fever in the year 1928. But as the virus was in a lab, it could be studied further. The researchers found that injecting monkeys with serum taken from immune humans could protect them from the fever. The serum was from infected people in Latin America and this proved that one vaccine could be made available throughout the world. However, the serum did not offer immunity against yellow fever. So, to begin with, rudimentary vaccines were made. But it was clear that the researchers needed a weak strain of the live virus to make the vaccine. So, Theiler came up with a solution. He injected the brains of lab mice to grow the virus and this virus was then given to rhesus monkeys. While the virus showed increase neurotropism, it caused less damage to the liver and other organs. This led to the first attenuated vaccine against yellow fever. In the meantime, Rockefeller Institute began its work and research on the vaccine too in the memory of its death researchers. The Institute used a highly weakened form of the virus on one its staff members who had just returned from Brazil. The vaccination only caused a mild swelling and redness at the injection site. Hence, paving way for more vaccines to be produced.

The French also produced their own vaccine at the Pasteur Institute, but it was found that the French vaccine cause central nervous system and febrile reactions. However, it could be utilized for vaccinating large population. The Rockefeller vaccine was used to inoculate people in the Western Hemisphere, while the one developed by the French was used in France and all the African colonies of the French. By the time the year 1945 came to an end, millions of people in Africa were vaccinated against yellow fever. Thereafter, people were inoculated against the disease every 4 years.

While later on the vaccine for yellow fever got modified still further, but the history of yellow fever vaccine started from here.

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History Of Yellow Fever Vaccine