Oral live-attenuated polio vaccines (OPV) and injected inactivated polio vaccines IPV) have helped eradicate wild polioviruses. However, there is still a need to develop new vaccines due to risk of outbreaks of vaccine-derived polioviruses. In the process of developing new vaccines, it is important to study the safety of the viruses and possible release into the environment. In this double-blind phase 1 trial, investigators randomized 30 participants to receive two novel monovalent oral type-2 poliovirus (OPV2) vaccine candidates in order to study the safety of the vaccines, the nature of viral shedding in participants, and the immunogenic effect of the vaccines. Investigators found that both OPV2 candidates increased the median blood titer of serum neutralizing antibodies, and all participants were seroprotected after vaccination. Severe events were reported in 40% of participants receiving candidate 1, and in 60% of participants receiving candidate 2; most events were increases in blood creatinine phosphokinase without accompanying clinical symptoms. There were no serious adverse events. In terms of shedding, 100% of participants receiving vaccine candidate 1 and 87% of participants receiving candidate 2 had vaccine virus detected in their stools. Viral shedding stopped after a median of 23 days (IQR 15-36 days) and 12 days (IQR 1-23) for candidates 1 and 2, respectively. Overall, the results from this study indicate an acceptable safety profile for the two vaccine candidates and a shedding rate that is not substantially increased compared to existing vaccines. As such, these candidates hold promise for future studies. Limitations for this study include the small sample size and the lack of placebo group.
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