Oral poliovirus vaccine (OPV) is a live, attenuated vaccine used to protect against poliomyelitis, commonly known as polio. Polio is a highly infectious viral disease caused by the poliovirus, which primarily affects children under the age of five. The virus is transmitted through fecal-oral route and can lead to paralysis or death in severe cases.
OPV is administered orally, usually in the form of drops, and is easily absorbed by the gastrointestinal tract, making it an effective method of vaccination, especially in areas with limited access to healthcare facilities. The vaccine contains weakened forms of the three types of poliovirus, resembling the wild poliovirus strains but with reduced virulence.
Once administered, OPV stimulates the body's immune system to produce specific antibodies that prevent infection and provide immunity against future exposure to the poliovirus. It triggers both the production of circulating antibodies in the bloodstream and the activation of a cellular immune response.
One of the notable advantages of OPV is its ability to induce immunity not only in the vaccinated individuals themselves but also in their close contacts, as the vaccine viruses are excreted in the stool for a short period after administration. This allows for indirect protection of the surrounding community through the potential interruption of poliovirus transmission chains.
OPV has played a crucial role in the globally coordinated efforts to eradicate polio. It has contributed significantly to the decline of polio cases worldwide, particularly in endemic countries. However, in rare instances, OPV itself can cause vaccine-associated paralytic polio, which is why countries have recently transitioned or are transitioning to the inactivated poliovirus vaccine (IPV) as part of their immunization strategies.
