1). Before proceeding to the next step, a data safety monitoring board (DSMB) evaluated the safety and tolerability results of the vaccines of the previous step. Subjects were observed for 30 min after vaccination. Parents/legal representatives of the subjects were requested to record any solicited or unsolicited adverse events that occurred in the subject in a diary during the

5 days after vaccination. When adverse reactions persisted longer than five days, they were to continue to monitor these reactions until they had resolved. Blood samples were taken before the first and 28 days (range 25–31 days) after the third vaccination. Concomitant drug use was not allowed except for antipyretics/analgesics (non-prophylactic). A follow-up telephone call was made 6 months after the last vaccination HIF inhibitor with the IMP to assess whether any serious adverse event had occurred during that period. Subjects that did not seroconvert for one or more poliovirus serotypes after three doses of the IMP would receive additional vaccinations with wIPV. Infants participating in the trial also received the regular booster dose at 15–18 months with wIPV. The

study was approved by the WHO Ethics Review Committee, in Poland by the Bioethics Committee at the District Medical Doctors’ Chamber in Krakow and the Office for Registration Veliparib of Medicinal Products, Medical Devices and Biocides (CEBK). The trial is registered in EU Clinical Trials Register with EudraCT number 2011-003792-11 and at Clinicaltrial.gov with number NCT01709071. Written informed consent has been obtained for

all participants. Principles of the Declaration of Helsinki were followed and the study was conducted adhering to good of clinical practice guidelines. The sIPV used in this study was manufactured by the Netherlands Vaccine Institute (NVI) in Bilthoven, the Netherlands, and produced under cGMP according to a slightly modified wIPV production process [15]. Infants received three doses of one of the following formulations of formaldehyde-inactivated poliovirus (strains Sabin-1, Sabin-2 and Sabin-3), with DU per human dose as shown in Table 1: Low, middle and high dose of sIPV (respectively lot nr PS1007, PS1008 and PS1009), and low, middle or high dose sIPV adjuvanted with 0.5 mg aluminum hydroxide (respectively lot nr PS1004, PS1005 and PS1006). The reference, wIPV (Mahoney, MEF-1 and Saukett), was produced by the NVI (Bilthoven, the Netherlands) and contained, respectively 40:8:32 DU of types 1, 2, and 3, per dose. Subjects received a dose of 0.5 mL intramuscularly in the right thigh with a 2 mL syringe and 0.5 mm × 25 mm needle. After coagulation, the serum was separated, frozen, and stored at −20 °C until shipment to the Centers for Disease Control and Prevention (CDC, USA).