**Question:** True about Oral polio vaccine

A. It has live attenuated poliovirus strains
B. It is administered only to pregnant women
C. It is effective against all three serotypes of poliovirus
D. It is contraindicated in patients with severe allergies

**Core Concept:** Poliovirus is the causative agent of polio, a neurotropic viral infection that affects the central nervous system. The oral polio vaccine (OPV) is a vaccination strategy developed to prevent polio. It consists of live attenuated strains of poliovirus, specifically the three serotypes: type 1, type 2, and type 3. These attenuated strains are weakened versions of the wild poliovirus, allowing the immune system to mount a response without causing the disease.

**Why the Correct Answer is Right:**

C. Oral polio vaccine (OPV) is effective against all three serotypes of poliovirus (types 1, 2, and 3) because it contains live attenuated virus strains that can stimulate the immune system to produce immunity against these specific serotypes. By including all three serotypes, OPV provides a broad protection against the different strains of poliovirus that cause the disease.

**Why Each Wrong Option is Incorrect:**

A. Administering OPV to pregnant women is not the primary target population. The vaccine is primarily given to infants and children to prevent polio transmission and protect the population at large. While pregnant women can develop immunity through the placenta, the focus is on the immunization of children and young adults to control polio epidemics.

B. Pregnant women are not contraindicated for OPV administration. The vaccine can be safely given to pregnant women as part of a comprehensive polio eradication strategy, with proper precautions taken to avoid accidental infection of the newborn.

D. Contraindications for OPV administration include severe allergies or history of severe anaphylaxis to any vaccine component. In this case, the correct answer is D, as those with severe allergies are not suitable candidates for the vaccine due to the risk of severe adverse reactions.

**Clinical Pearl:**

The oral polio vaccine (OPV) is a crucial tool in the global effort to eradicate polio. It is safe and effective in preventing polio transmission, and its administration to the primary target population (infants and children) is vital for controlling the disease. While pregnant women can develop immunity through the placenta, the focus is on the immunization of children and young adults to reduce the global polio burden. Vaccination campaigns and healthcare provider education play a vital role in ensuring the safe and appropriate use of OPV in various populations, including pregnant women.