True about oral polio vaccine –
**Core Concept**
Oral polio vaccine (OPV) is a live, attenuated vaccine used for the prevention of poliomyelitis. It contains weakened forms of the poliovirus, which induce immunity without causing the disease.
**Why the Correct Answer is Right**
OPV works by inducing a mucosal immune response in the gut, where the poliovirus initially enters the body. This is achieved through the replication of the weakened virus in the gut-associated lymphoid tissue (GALT), which stimulates the production of antibodies and immune cells that can recognize and neutralize the poliovirus. The live, attenuated virus in OPV also allows for the development of memory T cells, which provide long-term immunity against polio.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism of action of OPV.
**Option B:** This option is incorrect because it is not a characteristic of OPV; inactivated poliovirus vaccine (IPV) is the one that is given as an injection.
**Option C:** This option is incorrect because it is not a true statement about OPV; OPV is not a combination vaccine.
**Clinical Pearl / High-Yield Fact**
It's essential to note that OPV should not be administered to individuals with weakened immune systems, as the live, attenuated virus can cause vaccine-associated polio in these individuals. This is a critical consideration when administering OPV in areas with high polio transmission.
**Correct Answer:** B. Oral poliovirus vaccine is given as an oral dose.