Consider statements about human immunity: 1. Innate immunity is present from birth. 2. Acquired immunity develops after exposure to an antigen. 3. Vaccines provide natural immunity. Which are correct? MCQ with Answer and Explanation

Innate (natural) immunity is the non-specific defense mechanism present from birth, including physical barriers like skin and chemical barriers like stomach acid. Acquired (adaptive) immunity is highly specific and develops after the body is exposed to a specific pathogen or antigen, involving the production of antibodies and memory cells. Vaccines provide artificial immunity (specifically, artificial active immunity), not natural immunity, which is acquired through actual infection or from mother to child. Thus, statements 1 and 2 are correct.