Compare the following : (i) Sabin and Salk polio vaccine (ii) Active and Passive immunization.

(i) Sabin vs. Salk Polio Vaccine

Sabin Polio Vaccine (Oral Polio Vaccine, OPV):

• Type: Live attenuated vaccine.
• Administration: Oral.
• Immunity: Stimulates both systemic and local (intestinal) immunity. Provides good community immunity because it can be spread from person to person.
• Benefits: Easier to administer (oral) and usually less expensive. Can lead to herd immunity as it spreads through the community.
• Risks: Rare risk of vaccine-derived polio (VAPP), where the weakened virus in the vaccine can mutate and cause disease.

Salk Polio Vaccine (Inactivated Polio Vaccine, IPV):

• Type: Inactivated (killed) vaccine.
• Administration: Injection.
• Immunity: Primarily stimulates systemic immunity (protection in the bloodstream). Less effective at stimulating local immunity in the gut.
• Benefits: No risk of vaccine-derived polio. Safe and effective in preventing polio.
• Risks: More expensive and requires injections, which can be less convenient. Does not contribute to herd immunity as effectively as the OPV.

(ii) Active vs. Passive Immunization

Active Immunization:

• Definition: The process by which exposure to a disease triggers the immune system to produce antibodies and develop immunity.
• Method: Typically achieved through vaccination (e.g., with live attenuated, inactivated vaccines) or through natural infection.
• Duration: Generally provides long-lasting immunity, often years or even a lifetime.
• Mechanism: The body’s immune system learns to recognize and fight the pathogen if encountered again in the future.

Passive Immunization:

• Definition: The process of providing immediate, but temporary, protection against a disease by administering pre-formed antibodies.
• Method: Achieved through the transfer of antibodies from another source (e.g., through antibody-containing blood products, such as immunoglobulins, or from mother to baby via the placenta or breast milk).
• Duration: Provides short-term protection, typically lasting a few weeks to a few months.
• Mechanism: The immune system does not learn to recognize the pathogen; it relies on the external antibodies for protection.