What is the Difference Between Bivalent and Trivalent Polio Vaccine?

The main difference between bivalent and trivalent polio vaccines lies in the number of poliovirus types they protect against.

• Bivalent Oral Polio Vaccine (bOPV): This vaccine protects against poliovirus types 1 and 3. It elicits a better immune response against these types than the trivalent vaccine but does not provide immunity against serotype 2. Bivalent OPV is used in routine immunization and for outbreak response against poliovirus types 1 and 3.
• Trivalent Oral Polio Vaccine (tOPV): This vaccine protects against all three poliovirus types (1, 2, and 3). It was the predominant vaccine used for routine immunization until April 2016, when it was replaced by the bivalent OPV.

After the eradication of wild poliovirus type 2 in 2015, the global switch from trivalent to bivalent OPV was made to remove the type 2 strain from the vaccine. This reduces the risk of vaccine-associated poliomyelitis caused by the type 2 strain. However, since the bivalent vaccine does not protect against serotype 2, countries that use bOPV for routine immunization have added a single dose of inactivated polio vaccine (IPV) to protect against all three types of poliovirus.

Comparative Table: Bivalent vs Trivalent Polio Vaccine

The main difference between bivalent and trivalent polio vaccines lies in the number of serotypes they protect against. Here is a table comparing the two types of vaccines:

Bivalent polio vaccine only protects against serotypes 1 and 3, while trivalent polio vaccine protects against all three serotypes (1, 2, and 3).