What is the Difference Between OPV and IPV?

The main difference between the oral polio vaccine (OPV) and the inactivated polio vaccine (IPV) lies in their administration, effectiveness, and potential side effects. Here are the key differences:

1. Administration: OPV is given orally, as drops in the mouth, while IPV is administered as a shot in the leg or arm.
2. Effectiveness: Both vaccines protect against poliovirus types 1, 2, and 3. IPV is known to protect against symptomatic poliomyelitis and paralysis. On the other hand, OPV elicits a stronger intestinal immunity, which is more effective in preventing viral shedding and transmission to others.
3. Side Effects: IPV is generally considered safer, with fewer risks of serious side effects compared to OPV. OPV has been associated with a higher risk of vaccine-derived poliovirus.
4. Usage: IPV is the only polio vaccine used in the United States and has been since 2000. OPV is still used in many parts of the world.
5. Sequential Vaccination: Some studies have suggested that a sequential vaccination schedule involving both IPV and OPV may reduce the risk of vaccine-associated paralytic poliomyelitis (VAPP) without affecting vaccination coverage, safety, or humoral response, except for poliovirus type 2 (P2). However, the impact on P2 titers is not clear.

In summary, while both OPV and IPV are effective in protecting against poliovirus, IPV is generally considered safer and is the only polio vaccine used in the United States. OPV is still used in many parts of the world, but its use is associated with a higher risk of vaccine-derived poliovirus.

Comparative Table: OPV vs IPV

Here is a table comparing the key differences between Oral Polio Vaccine (OPV) and Inactivated Poliovirus Vaccine (IPV):

OPV is more convenient to use and has lower production costs, making it more popular in low- and middle-income countries. However, it can revert to a form that causes paralysis, leading to VAPP outbreaks. In contrast, IPV does not carry the risk of VAPP but requires injections and may not provide as much mucosal immunity. Sequential immunization schedules involving IPV and OPV are sometimes used to reduce VAPP risk without affecting vaccination coverage, safety, or humoral response.