 The trial is conducted in two parts. In the first part, 50 of the subjects are randomised with allocation weights 4:4:1:1 to IPV SSI, 13 IPV-Al SSI, 15 IPV-Al SSI or 110 IPV-Al SSI, respectively. In the second part, the corresponding allocation weights are 1:1:4:4 for the remaining 50 of the subjects. 