Assertion (A) : Syphilis can be prevented by vaccination. Reason (R) : Vaccinat ion trigger s the production of antibodies in the body.

Assertion (A) is false because there is currently no vaccine available for syphilis [t1, t2, t5]. Syphilis is caused by the spirochete Treponema pallidum, and while research has been ongoing since 1912, no immunization experiment has yet yielded an effective vaccine for human use [t6, t8]. Development is hindered by the pathogen's complex immune evasion mechanisms and the difficulty of identifying surface-exposed antigens [t7, t10]. Reason (R) is true as a general biological principle; vaccination works by introducing weakened or inactive pathogens (or parts of them) to trigger the body's immune system to produce specific antibodies and memory cells [c1, c2]. This process prepares the immune system to recognize and fight the actual pathogen in the future. Since the assertion is false and the reason is a true statement about vaccine mechanisms, option 4 is the correct choice.

Sources

1. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6089657/
2. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC5513191/
3. [3] https://www.sciencedirect.com/science/article/pii/S0264410X25007030
4. [4] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 3: Health: The Ultimate Treasure > Application > p. 39