A way to test if the 96% to 100% effectiveness of the Sabin vaccine is in conducting a research using test animals. Since the previous test was done on humans, there is no certainty that it worked (in reality) the effective. Some of the people who were vaccinated might not ever come in contact with the disease and therefore can't count as part of the 'effectiveness' group. The only way to test how effective it is, is to infect the people with the polio virus and see how many actually get infected with the disease. Since this would pose an problem with moral of infecting people with the disease, the test should be done with animals. You would give the animals the vaccine and then infect them with the full blown polio virus. The number of animals infected with the disease would tell you the true effectiveness of the vaccine. This test, however, also assumes something. It assumes that the virus that infects the animals won't be mutated so that it is safe for the animals, but unsafe for humans.
It states that the Sabin vaccine lasts longer than the Salk vaccine. It is assumed that there is a great significance of time between how long the Sabin vaccine lasts compared to how long the Salk vaccine lasts. To make certain, you should find out how much longer. If it is only longer by a few months or days, than it's not that great of an advantage. You would still have to take multiple doses through out your life time with either. The test for this would be harder since it would have to be conducted over the lifetime of a person and the results won't appear for quite a long time.
The helpfulness of the oral vaccine in the third world countries is assumed that the person taking the vaccine doesn't have any other microorganisms that might prevent the vaccine from taking effect. The vaccine is indeed great for third world countries since it doesn't matter as much as the injected vaccine if the place is sanitary. And most of the time, the place is unsanitary. The use of dirty needles could spread other diseases. However, if there's other microorganisms in the body, it might hamper the weakened polio virus from having full effect. The vaccine would then have completed nothing since the person still isn't immune to it.
Contracting the polio virus secondhandedly isn't always helpful. It's helpful if the virus contracted is still weakened. However, the virus in the feces might become wild and dangerous. Instead of being a weakened polio virus, it could become a regular polio virus. Instead of becoming immune to the virus, you would have the virus and become infected with polio. This deviates from the purpose of the vaccine, which is to prevent, not cause, polio.
What is the best answer? Is there one? Both Sabin's and Salk's vaccines have been approved for use. 99% of the polio vaccination's used in this country is Sabin's, but that doesn't mean it is more effective or necessarily better. A lot of it has to do with politics and companies that make the vaccines.