A Randomized Phase 4 Study of Immunogenicity and Safety After Monovalent Oral Type 2 Sabin Poliovirus Vaccine Challenge in Children Vaccinated with Inactivated Poliovirus Vaccine in Lithuania

J Infect Dis. 2021 Jan 4;223(1):119-127. doi: 10.1093/infdis/jiaa390.


Background: Understanding immunogenicity and safety of monovalent type 2 oral poliovirus vaccine (mOPV2) in inactivated poliovirus vaccine (IPV)-immunized children is of major importance in informing global policy to control circulating vaccine-derived poliovirus outbreaks.

Methods: In this open-label, phase 4 study (NCT02582255) in 100 IPV-vaccinated Lithuanian 1-5-year-olds, we measured humoral and intestinal type 2 polio neutralizing antibodies before and 28 days after 1 or 2 mOPV2 doses given 28 days apart and measured stool viral shedding after each dose. Parents recorded solicited adverse events (AEs) for 7 days after each dose and unsolicited AEs for 6 weeks after vaccination.

Results: After 1 mOPV2 challenge, the type 2 seroprotection rate increased from 98% to 100%. Approximately 28 days after mOPV2 challenge 34 of 68 children (50%; 95% confidence interval, 38%-62%) were shedding virus; 9 of 37 (24%; 12%-41%) were shedding 28 days after a second challenge. Before challenge, type 2 intestinal immunity was undetectable in IPV-primed children, but 28 of 87 (32%) had intestinal neutralizing titers ≥32 after 1 mOPV2 dose. No vaccine-related serious or severe AEs were reported.

Conclusions: High viral excretion after mOPV2 among exclusively IPV-vaccinated children was substantially lower after a subsequent dose, indicating induction of intestinal immunity against type 2 poliovirus.

Keywords: immunogenicity; inactivated poliovirus vaccine; oral poliovirus vaccine; poliovirus; vaccine; viral shedding.

Publication types

  • Clinical Trial, Phase IV
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Neutralizing
  • Child, Preschool
  • Female
  • Humans
  • Immunogenicity, Vaccine
  • Infant
  • Intestines / immunology
  • Lithuania
  • Male
  • Poliomyelitis / immunology*
  • Poliomyelitis / prevention & control
  • Poliovirus Vaccine, Inactivated / administration & dosage
  • Poliovirus Vaccine, Oral / administration & dosage
  • Poliovirus Vaccine, Oral / adverse effects
  • Poliovirus Vaccine, Oral / immunology*
  • Virus Shedding


  • Antibodies, Neutralizing
  • Poliovirus Vaccine, Inactivated
  • Poliovirus Vaccine, Oral

Associated data

  • ClinicalTrials.gov/NCT02582255