Most vaccines are equally effective in most populations. An exception to this rule was the TB vaccine BCG. When administered to college students in the United States during the mid-1950s, it was very...

Most vaccines are equally effective in most populations. An exception to this rule was the TB vaccine BCG. When administered to college students in the United States during the mid-1950s, it was very effective (about 80%) in preventing TB. In Bangladesh, the efficacy of the same vaccine was close to 0%. What are some of the reasons this could happen? Suppose that the vaccine was of high quality and the cold chain (refrigeration conditions) had been maintained but the disparity still occurred. Try to explain this. Hint (and this is highly speculative): there are bacteria related to M. tuberculosis that are found widely in the Indian subcontinent. How could this fact have affected the outcome? Remember, the percent effectiveness is the effectiveness above prevailing rates of TB.