Final answer:
The oral polio vaccine (OPV), known as the Sabin vaccine, is not commonly used in places with very low polio rates due to the risk of vaccine-associated paralysis (VDPV). The inactivated polio vaccine (the Salk vaccine), which cannot cause VDPV, is preferred in these areas.
Step-by-step explanation:
Why isn't the oral polio vaccine given anymore?
The oral polio vaccine (OPV), also known as the Sabin vaccine, is not commonly given in countries with a near-zero infection rate primarily due to the risk of vaccine-associated paralysis. While OPV is effective and has been instrumental in reducing polio worldwide, it contains a weakened form of the live virus. This live virus can, in rare cases, mutate and cause polio in vaccine recipients or their close contacts, a condition known as vaccine-derived poliovirus (VDPV). In contrast, the Salk vaccine, which is an inactivated polio virus introduced in 1955, does not carry this risk and is administered by intramuscular injection.
Further, countries aiming to maintain a polio-free status tend to use the inactivated polio vaccine (IPV), or the Salk vaccine, to avoid the risk associated with the live, attenuated vaccine. IPV is safe as it does not contain the live virus and thus cannot lead to VDPV. Both vaccines are effective against all three serotypes of poliovirus, but the use of IPV is considered more practical in countries where polio has been nearly or completely eradicated.