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Inactivated polio vaccine (IPV)

Inactivated polio vaccine (IPV) was developed in 1955 by Dr Jonas Salk. Also called the “Salk vaccine”, IPV consists of inactivated (killed) poliovirus strains of all three poliovirus types. IPV is given by intramuscular injection and needs to be administered by a trained health worker.

A baby receives the IPV injection
A baby receives the inactivated polio vaccine from a qualified nurse
CDC/Judy Schmidt

The inactivated polio vaccine produces antibodies in the blood to all three types of poliovirus. In the event of infection, these antibodies prevent the spread of the virus to the central nervous system and protect against paralysis.

Advantages

  • As IPV is not a 'live' vaccine, it carries no risk of vaccine-associated polio paralysis.
  • IPV triggers an excellent protective immune response in most people.

Disadvantages

  • IPV induces very low levels of immunity in the intestine. As a result, when a person immunized with IPV is infected with wild poliovirus, the virus can still multiply inside the intestines and be shed in the faeces, risking continued circulation.
  • IPV is over five times more expensive than oral polio vaccine.
  • Administering the vaccine requires trained health workers and sterile injection equipment and procedures.

Safety

IPV is one of the safest vaccines in use. No serious systemic adverse reactions have been shown to follow vaccination.

Efficacy

IPV is highly effective in preventing paralytic disease caused by all three types of poliovirus.

Recommended use

An increasing number of industrialized, polio-free countries are using IPV as the vaccine of choice. This is because the risk of paralytic polio associated with continued routine use of oral polio vaccine (OPV) is deemed greater than the risk of imported wild virus.

However, as IPV does not stop transmission of the virus, oral polio vaccine is used wherever a polio outbreak needs to be contained, even in countries which rely exclusively on IPV for their routine immunization programme (e.g. the polio outbreak in the Netherlands in 1992).

IPV is not recommended for routine use in polio-endemic countries or in developing countries at risk of poliovirus importations. In these countries, oral polio vaccines – either trivalent, bivalent or monovalent, depending on local epidemiology – are used.

Once polio has been eradicated, use of the oral polio vaccine will need to be stopped to prevent re-establishment of transmission due to vaccine-derived polioviruses. Switching to IPV is one option for this post-OPV era.