Phase 1 Novel Live Attenuated Serotype 2 Oral Polio Vaccine Study in Inactivated Polio Vaccine (IPV) Primed Adults

In stool samples that were positive for type-2 poliovirus detected by RT-PCR, infectious virus was measured as 50% cell culture infective dose (CCID₅₀) per gram of stool by use of a modification of the World Health Organization (WHO) cell sensitivity assay.

Time frame: Days 1, 2, 3, 4, 5, 6, 7, 14, 21, and 28

Population: All randomized participants who received study vaccine and with type 2 poliovirus-positive stool samples at each time point.

Serious adverse events are medical events that resulted in death, were life-threatening, required admission to hospital, or resulted in notable incapacity of the individual. Adverse events were also graded from mild to severe; Severe adverse events are medical events that prevent normal everyday activities or fever \> 39°C; this category does not include serious adverse events. Serious adverse events and severe adverse events include both solicited and unsolicited events. Solicited events comprised signs and symptoms that were reported by the participant using a predefined checklist in a diary card, or a fever, as determined by the participant's measurement of their body temperature, for up to 7 days after vaccination. Unsolicited events comprised other signs and symptoms recorded through the end of the study. Adverse events were assessed by the investigator for causality as unrelated, unlikely, possibly, or probably related to the vaccination.

Time frame: From Day 0 up to 42 days

Population: All randomized participants who received a dose of study vaccine.

Participants provided stool samples for assessment of viral shedding, defined as the presence of type 2-specific poliovirus ribonucleic acid (RNA) in stools. Samples were analyzed by the US Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA) for the presence of type-2 poliovirus genome using a Sabin multiplex real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay of total nucleic acid extracted from stool suspensions (50% weight to volume in cell culture medium).

Time frame: Days 0, 1, 2, 3, 4, 5, 6, 7, 14, 21, and 28

Population: All randomized participants who received study vaccine with available stool samples at each time point.

A combined index of the prevalence, duration, and quantity of viral shedding in all participants. The viral shedding index was calculated for each participant as the mean of log₁₀(CCID₅₀/g) of samples collected 7, 14, 21, and 28 days after vaccine administration, with the lower limit of quantitation (2.75 log₁₀) as an observed value, and all titers in stool samples with negative shedding results (real-time RT-PCR-negative values) contributing 0 to the mean.

Time frame: Days 7, 14, 21, and 28

Population: All randomized participants who received a dose of study vaccine. Missing values (from missing samples on specific study days) were replaced with values from the days before or after or the average of these two values, as necessary.

The time to cessation of shedding was defined as the time interval between administration of vaccine and the date of the first sample negative for type 2 poliovirus shedding (assessed by RT-PCR) after which the following two consecutive samples were also negative. Time to cessation of viral shedding was assessed using Kaplan-Meier methods; participants were right-censored if they had not met this endpoint with the last stool sample collected.

Time frame: Stool samples were collected from the day of vaccination to Day 28 or until shedding cessation; up to 89 days (novel OPV2 candidate 1) and 48 days (novel OPV candidate 2).

Population: All randomized participants who received a dose of study vaccine with at least one type 2 poliovirus-positive stool sample.

Neutralizing antibodies against poliovirus type 2 were determined using the WHO standard microneutralization assay (WHO EPI GEN 93.9).

Time frame: Day 0 and Day 28

Population: All randomized participants who received study vaccine and had no exclusion criterion or major protocol deviations.

Neurovirulence of shed virus was measured using a modified WHO poliovirus receptor transgenic mouse neurovirulence test (mTgmNVT). The last stool sample provided by each participant that had adequate concentrations of virus for the neurovirulence assay (≥ 4 log₁₀\[CCID₅₀/g\]) was used in the test. For each stool specimen thirty Tg-PVR21 mice were administered intraspinal inoculations of 4 log₁₀(CCID₅₀) amplified virus. After 14 days the inoculated mice were assessed as either paralyzed or non-paralyzed. For each participant/sample, the percentage of paralyzed mice was calculated. Overall percent paralysis is the average percentage of paralyzed mice over all participants in each group.

Time frame: Samples tested were the last post-vaccination sample per participant suitable for analysis; samples used in the analysis ranged from Day 2 to Day 56

Population: Participants with stool samples evaluable by the neurovirulence test; in the nOPV2-Candidate 2 group only six participants shed sufficient virus at any time point to attempt virus amplification, and amplification did not work for four of these.

Clinical laboratory test values were evaluated according to Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 (toxicity grades) or in accordance with the normal ranges of the clinical laboratory (below, within, or above normal range) for parameters for which no toxicity grades were defined. Clinical chemistry assessments included total bilirubin, glucose, blood urea nitrogen (BUN), creatinine, calcium, inorganic phosphate, potassium, sodium, alanine aminotransferase, aspartate aminotransferase, and C-reactive protein (CRP). Hematology assessments included hemoglobin, hematocrit, red blood cells, and white blood cells with differential.

Time frame: Screening, Day 7, Day 14, and Day 28

Population: All randomized participants who received study vaccine

Adverse events were solicited from the participants by the medical team during the 7 days after vaccination. Solicited events comprised signs and symptoms that were reported with a predefined checklist in a diary card, including headache, fatigue, myalgia, arthralgia, paresthesia, anesthesia, paralysis, nausea, vomiting, diarrhea and abdominal pain, or fever defined as a temperature of 37.5°C or higher. Adverse events were graded as mild (easily tolerated), moderate (sufficiently discomforting to interfere with normal everyday activities), or severe (preventing normal everyday activities, or temperatures higher than 39.0°C). Adverse events were assessed by the investigator for causality as unrelated, unlikely, possibly, or probably related to the vaccination.

Time frame: Day 0 to Day 7

Population: All randomized participants who received a dose of study vaccine.

Unsolicited events comprised other signs and symptoms that participants reported through the end of the study. Each unsolicited AE was rated on a 3-point scale of increasing intensity: * Grade 1: Mild; an AE that was easily tolerated by the subject, causing minimal discomfort and not interfering with everyday activities. * Grade 2: Moderate; an AE that was sufficiently discomforting to interfere with normal everyday activities. * Grade 3: Severe; an AE that prevented normal everyday activities. Each adverse event was assessed by the investigator for causality as unrelated, unlikely, possibly, or probably related to the vaccination.

Time frame: From Day 0 up to 42 days

Population: All randomized participants who received a dose of study vaccine.

Seroconversion rate is defined as the percentage of participants in each group with a change from seronegative to seropositive (poliovirus type-2-specific neutralizing antibody titers ≥ 1:8) or, in participants seropositive at Baseline, an increase in neutralizing antibody titer of at least four-fold from Baseline.

Time frame: Day 28

Population: Randomized participants who received study vaccine with no exclusion criterion or major protocol deviations. Five participants (2 in the nOPV2-Candidate 1 group, 3 in the nOPV2-Candidate 2 group) with pre-vaccination type 2- neutralizing antibody titers too close to the upper limit of quantitation to measure a 4-fold increase are excluded.

Seroprotection rate was defined as the percentage of participants in each group with anti-type 2-specific poliovirus neutralizing antibodies titers ≥ 1:8.

Time frame: Day 0 and Day 28

Population: All randomized participants who received study vaccine and had no exclusion criterion or major protocol deviations.