Laboratory staff FK228 was unaware of the vaccination group of the subjects whose specimens they were analyzing. The initial dilution was a reciprocal titer of 8 (log2(titer) = 3). When no virus neutralization was detected, this was recorded as a log2(titer)

of 2.5. As the number of subjects experiencing local or systemic reactions was small, only descriptive statistics were performed for this endpoint. For immunogenicity analysis, median antibody titers of two independent determinations (pre- and post-vaccination), the increase in antibody titer pre- versus post-vaccination, and seroprotection rates were determined. The internationally accepted threshold value for protection (≥8 or log2(titer) ≥3) was used to calculate the seroprevalence before and after vaccination and the seroconversion rate per vaccine group. Seroconversion was defined as a change from seronegative to seropositive (log2(titer) ≥3) or a four-fold increase over the expected decline in maternally derived antibody titers (assumed half-life is 28 days). Descriptive statistics was performed for continuous variables, whereas frequency counts were used for categorical data. This work was supported by the World Health Organization using funds provided by a grant from the Bill and Melinda Gates Foundation. The World Health Organization was involved in the design of the clinical trial.

In total, 142 infants were screened and 140 infants were HA 1077 included in the study and randomly assigned to one of the treatment groups (Fig. 1). Demographics of the subjects were similar for both groups as shown in Table 2. All enrolled subjects (140) were included in the safety analysis. In total, 139 unless subjects completed the study and received three doses of the IMP. One subject in the high-dose sIPV group discontinued after two vaccinations with the IMP due to communication problems with the parents. The subject received a third dose consisting of wIPV and had protective titers for all poliovirus types of both wild and Sabin-strains. In addition, two subjects received one dose of IMP out of the time window that was defined in the protocol and were excluded from immunogenicity

analysis. Except for fever, the frequency of solicited adverse events was highest after the first vaccination with the IMP and decreased with successive doses. After the first dose, 44% of subjects experienced at least one systemic adverse event and 16% reported at least one local adverse event. After the second and third vaccination, only 29% and 17%, respectively, reported systemic and 9% and 6.5% of subjects reported local adverse events. The frequency per group for each solicited adverse event after the first dose of the IMP is shown in Table 3. The frequency of fever (rectal temperature of ≥38.0 °C) increased with successive doses (4.3%, 6.4% and 7.9% of the total study population after doses 1, 2 and 3, respectively, not shown) but was generally mild (38.0–38.