Which of the following statements are correct about vaccines? (A). Vaccines have eliminated smallpox and polio. (B). The flu vaccine produced by Bacillus subtilis is an oral vaccine. (C). The oral vaccines are expensive and difficult to store. (D). The immunogenic proteins of certain pathogens are found to be active when taken orally. Choose the correct answer from the options given below:

Step-by-step solution

Statement (A) is correct because vaccines have successfully eradicated smallpox globally and eliminated polio from many countries. Statement (B) is correct as genetically engineered Bacillus subtilis spores are used to produce oral vaccines, such as the flu vaccine. Statement (C) is incorrect because oral vaccines, particularly those based on bacterial spores, are highly stable, do not require a strict cold chain, and are cost-effective and easy to store. Statement (D) is correct because for an oral vaccine to be e