Karnataka PGET 2007 PSM MCQ Answer 3

The correct answer is A

Community immunity or "herd immunity" is an important part of protecting the community against disease. Because vaccinated people have antibodies that neutralize a germ, they are much less likely to transmit that germ to other people. Thus, even people who have not been vaccinated (and those whose vaccinations have become weakened or whose vaccines aren't fully effective) often can be shielded by the herd immunity because vaccinated people around them are not getting sick. Herd immunity is more effective as the percentage of people vaccinated increases. It is thought that approximately 95% of the people in the community must be protected by a vaccine to achieve herd immunity. People who are not immunized increase the chance that they and others will get the disease.

For some diseases, however, herd immunity offers no protection. For example, tetanus is not contagious. It is contracted when a wound comes in contact with soil contaminated with the tetanus bacterium. It is important to keep in mind that a few people may not be protected from the disease even though they have been vaccinated. About 1 or 2 of every 20 people immunized will not have an adequate immune response to a vaccine. But if 95% of the population is immunized, then the unprotected people are not as likely to be exposed to the germ at all, so they have a smaller chance of becoming infected.

Category: Karnataka PGET 2007 MCQs