US Considers Switching To Killed Polio Virus Vaccine

The US Advisory Committee on Immunization Practices is gearing up to make a decision in October over whether to switch from the current recommended oral polio vaccine (OPV), which is made from a live attenuated virus) to an injectable vaccine based on killed virus.

OPV is given to some four million American children every year, and is the only form which stimulates mucosal immunity. Poliovirus infection is transmitted via the alimentary route, so mucosal immunity is particularly important as it helps prevent invasion of the mucosal cells and the creation of carrier states. OPV also sheds some att7enuated virus into the community, which may give some protection to the unimmunized.

However, because OPV also gives polio to about eight people (a mix of children and adults) a year in the USA, some quarters are saying that it is hard to justify the risk and a switch to an inactivated polio vaccine (IPV) should be made. IPV, a stronger version of the vaccine invented by the late Jonas Salk, causes only serum immunity and does not prevent a carrier from infecting the unimmunized (see table for other pros and cons of IPV and OPV).