The trial is a phase 4, open-label, multicentre clinical trial with healthy subjects who have been vaccinated with IPV-Al AJV at 2, 4, 6 and 15 18 months of age in previous trials. Levels of antibodies against poliovirus types 1, 2 and 3 after immunisation with IPV Al AJV will be measured in the trial subjects at the age of 4 years. An additional IPV-Al AJV dose (investigational vaccine) will be administered and the booster response to IPV-Al AJV will be investigated one month after administration.

Inclusion Criteria:

1. Children that have been vaccinated with IPV-Al AJV in the VIPV-07 and VIPV-07 E1 trials and have completed these trials
2. Healthy, as assessed from medical history and physical examination
3. Parent(s)/guardian(s), according to the local legal requirements, have been properly informed about the trial and have signed the informed consent form
4. Parent(s)/guardian(s), according to the local legal requirements, have been granted access to the child´s trial related medical records
5. Parent(s)/guardian(s), according to the local legal requirements, are likely to comply with trial procedures

Exclusion Criteria:

1. Previous vaccination with OPV
2. Previous vaccination with IPV outside the VIPV-07 and VIPV-07 E1 trials
3. Known or suspected immunodeficiency (e.g. leukaemia, lymphoma) or family history of congenital or hereditary immunodeficiency. HIV is not an exclusion criterion.
4. Severe uncontrolled chronic (e.g. neurologic, pulmonary, gastrointestinal, hepatic, renal or endocrine) disease
5. Known or suspected allergy to vaccine constituents (e.g. hypersensitivity to formaldehyde and/or 2-phenoxy-ethanol)
6. Uncontrolled coagulopathy or blood disorder contraindicating intramuscular injections or blood sampling
7. Treatment with a product which is likely to modify the immune response (e.g. blood products and immunoglobulins) prior to inclusion or planned during the trial period
8. Participating in another interventional clinical trial
9. Not suitable for inclusion in the opinion of the investigator