Difficulties
As it is in any mission, the eradication team faced many challenges along the way. The major issue lay in vaccination and how it was done. These two issues prevented the team from eradicating smallpox where it was at its worst.
A Better Vaccine
One setback to the eradication program was the lack of refrigeration and absence of a heat-stable vaccine. This prevented the WHO team from vaccinating tropical countries.
"Despite the conquest of smallpox in the United States and Europe, the disease continued to rage unabated in much of the developing world, particularly in tropical countries where the refrigeration of smallpox vaccine was impractical. Because the liquid vaccine was not heat-stable, it deteriorated rapidly unless it was maintained at a temperature of 41 to 50 degrees Fahrenheit from the time the vaccine was produced until it was inoculated into a human subject, a technical requirement known as the "cold chain". Some attempts were made to keep the vaccine chilled by transporting it in portable kerosene refrigerators on muleback, but this approach was exceedingly cumbersome and vaccine spoilage remained a major problem. As a result, vaccination induced effective immunity in fewer than 30 percent of recipients in tropical countries.
In the 1930s, Dutch and French scientists perfected air-dried vaccine preparations that remained potent at room temperature for as long as a month and could be rehydrated shortly before use. Although often heavily contaminated with bacteria and of variable potency, such air-dried vaccines were used successfully in Dutch Indonesia and in the French colonies of Africa and Asia. A further technical breakthrough came in the early 1950s, when Leslie H. Collier at the Lister Institute in London developed a procedure for manufacturing stable, freeze-dried smallpox vaccine on a commercial scale. Collier published his method and made it freely available to all laboratories that wished to use it. Vaccine technology had now progressed to the point where smallpox eradication had become a feasible proposition."
- Jonathan B. Tucker; Scourge: The Once and Future Threat of Smallpox
In the 1930s, Dutch and French scientists perfected air-dried vaccine preparations that remained potent at room temperature for as long as a month and could be rehydrated shortly before use. Although often heavily contaminated with bacteria and of variable potency, such air-dried vaccines were used successfully in Dutch Indonesia and in the French colonies of Africa and Asia. A further technical breakthrough came in the early 1950s, when Leslie H. Collier at the Lister Institute in London developed a procedure for manufacturing stable, freeze-dried smallpox vaccine on a commercial scale. Collier published his method and made it freely available to all laboratories that wished to use it. Vaccine technology had now progressed to the point where smallpox eradication had become a feasible proposition."
- Jonathan B. Tucker; Scourge: The Once and Future Threat of Smallpox
Vaccination Techniques "The vaccine--- its quality and quantity--- was one hurdle. Administering it was another. The techniques in use were not ideal. Since Jenner's day, doctors had used a number of different techniques for implanting the vaccinia virus into the superficial skin layers where it could multiply and cause a protective infection. Most vaccinations were performed by placing a drop of vaccine on the skin and making multiple scratches through the drop, using a small lancet. In the United States, a needle was placed parallel to the skin and the virus was pressed lightly beneath the skin using the tip. This technique, called multiple pressure vaccination, was less traumatic than previous methods, but there were many vaccination failures. In Southeast Asia, the most common method used was a "rotary lancet". Five short prongs protruded from a small metal plate. The plate was pressed firmly into the skin over the drop of vaccine and given a short twist. Four of these were performed on the forearm or upper arm. The insertions were painful and often became infected. In areas where these were in use--- primarily India--- resistance to vaccination was not uncommon, and some officials wondered why."
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"In the early 1960s investigators at the US Communicable Disease Center (CDC) experimented with a jet-injector gun. As many as one thousand people could be vaccinated in one hour. Unfortunately, the guns--- although high-performance--- broke down frequently so that a trained technician had to travel with each team; one or two backup guns were needed for each one in operation."
- D.A. Henderson; Smallpox: The Death of a Disease
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The bifurcated needle, invented by Wyeth Laboratory scientist, Dr. Benjamin Rubin in 1967, was the ultimate vaccination solution. It is two inches long with a two pronged fork at the end. The fork prevented the needle from penetrating too deeply.
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In the early 1950's, Dr. Leslie Collier developed a method for producing a freeze-dried vaccine which was heat-stable for a month even when exposed to a temperature of 37 degree Celsius. The heat-stable vaccine proved critical for use in tropical countries.
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