Oral Sabin Polio vaccine is which type of vaccine ?

Concept: Vaccines are classified by their composition and how they trigger immunity — live attenuated vaccines contain a weakened but still-living pathogen that replicates in the body and mimics natural infection; inactivated vaccines contain a killed pathogen that cannot replicate; acellular/subunit vaccines contain only purified antigenic fragments of the pathogen; and recombinant vaccines contain an antigen manufactured by inserting the pathogen's gene into another host organism.

Application: The oral Sabin polio vaccine (OPV) contains a poliovirus that has been weakened (attenuated) in the laboratory so that it does not ordinarily cause paralytic disease — though in very rare cases the vaccine strain can revert and cause vaccine-associated paralytic poliomyelitis — while still being able to replicate in the lining of the intestine after being swallowed. This replication closely mimics natural poliovirus infection, producing strong intestinal (mucosal) immunity along with systemic antibody protection, and can even spread limited contact immunity to unvaccinated people nearby.

• Acellular vaccines use only purified pathogen components, not a whole living virus, so OPV (which uses the entire weakened virus) does not fit this category.

• The inactivated (killed) polio vaccine is the injectable Salk vaccine (IPV); it cannot replicate in the body, unlike the oral Sabin vaccine, which does.

• Recombinant vaccines are produced by inserting a pathogen's antigen gene into a different host organism (as with the hepatitis B vaccine), whereas OPV uses the poliovirus itself rather than a gene-engineered antigen.

Result: Because OPV contains a live poliovirus that is weakened yet still able to replicate and closely mimic natural infection, it is classified as a Live Attenuated Vaccine.