Which vaccine is a live attenuated vaccine?

• A. Rotavirus
• B. DTaP
• C. Haemophilus influenzae type B (HIB)
• D. IPV

Answer: (A)

Live attenuated vaccines use a weakened form of the pathogen that can still replicate in the body, which helps produce a strong, lasting immune response by mimicking natural infection. Rotavirus vaccine fits this because it contains live, attenuated rotavirus strains and is given orally to infants; the virus replicates in the gut to trigger both mucosal and systemic immunity against rotavirus. The other options are not live vaccines: DTaP is made from inactivated toxins and pertussis components, HIB is a conjugate polysaccharide vaccine, and IPV is an inactivated polio vaccine given by injection.