This article is more than 5 years old. Information may no longer be current.
Infant vaccine schedule with bOPV noninferior to IPV
Sequential schedules of inactivated poliovirus vaccines and bivalent oral poliovirus vaccines appeared to be noninferior compared with an inactivated poliovirus vaccine schedule alone, according to recent findings.
“This novel set of data for [inactivated poliovirus vaccines (IPV)]-[bivalent oral poliovirus vaccines (bOPV)] sequential schedules will be essential for policy formulation by national and global authorities to enable and sustain polio eradication,” researchers wrote in The Lancet Infectious Diseases.
For an open-label, control study, researchers randomly allocated 570 healthy, full-term infants from Santiago, Chile, to receive one of three polio vaccination schedules at ages 8, 16 and 24 weeks. One hundred ninety infants received a vaccination sequence of IPV-bOPV-bOPV; 192 infants received IPV-IPV-bOPV; and 188 infants received IPV-IPV-IPV. The IPV was administered via injection, and bOPV was dosed as oral drops.
The primary outcomes were seroconversion noninferiority (within a 10% margin) of the vaccination schedules, and 28-week measures of titers (within two-thirds log2 titers) to poliovirus serotypes 1 and 3, which were assessed in a per-protocol cohort of 537 vaccinated infants. The secondary outcomes were poliovirus serotype 2 seroconversion and titers, and fecal shedding 4 weeks after a monovalent OPV type 2 poliovirus challenge, which occurred at 28 weeks.
Seroconversion to type 1 poliovirus was achieved in:
- 98.8% (95% CI, 95.8-99.7) of patients who received IPV-bOPV-bOPV;
- 100% (95% CI, 97.9-100) of patients who received IPV-IPV-bOPV; and
- 100% (95% CI, 97.9-100) of patients who received IPV-IPV-IPV.
Seroconversion to type 3 poliovirus was observed in:
- 98.2% (95% CI, 94.8%-99.4) of patients who received IPV-bOPV-bOPV;
- 100% (95% CI, 97.9-100.0) of patients who received IPV-IPV-bOPV; and
- 98.9% (95% CI, 95.9-99.7) of patients who received IPV-IPV-IPV.
The data established the noninferiority of the schedules, with no significant disparities between the groups, the researchers wrote.
Seroprotective titers of type 1 poliovirus were reported in:
- 98.8% (95% CI, 95.8%-99.7%) of patients who received IPV-bOPV-bOPV;
- 100% (95% CI, 97.9-100) of patients who received IPV-IPV-bOPV; and
- 100% (95% CI, 97.9-100) of patients who received IPV-IPV-IPV.
Seroprotective titers of type 3 poliovirus were reported in:
- 98.2% (95% CI, 94.9-99.4) of patients who received IPV-bOPV-bOPV;
- 100% (95% CI, 97.9-100) of patients who received IPV-IPV-bOPV; and
- 98.9% (95% CI, 96-99.7) of patients who received IPV-IPV-IPV.
Since median titers for groups receiving OPV-containing schedules were higher than the assay’s upper limits of detection, noninferiority analyses could not be completed for this outcome.
Seroconversion of type 2 poliovirus was reported in:
- 77.4% (95% CI, 70.5-83) of patients who received IPV-bOPV-bOPV;
- 96% (95% CI, 92-98) of patients who received IPV-IPV-bOPV; and
- 100% (95% CI, 97.8-100) of patients who received IPV-IPV-IPV.
A nearly 0.3 log reduction of type 2 fecal shedding was observed in the IPV-bOPV schedules vs. the IPV-only schedule. Eighty-one serious adverse events occurred during the trial, one of which was suspected to be vaccine-related. None of the infants died during the study.
According to the researchers, the lack of immunity to type 2 poliovirus seen after administration of bOPV can be counterbalanced by administering one of more IPV doses before bOPV.
“This strategy will ensure infants will have adequate protection against accidental exposure to type 2 virus after the withdrawal of all type 2-containing live vaccines, as recommended by [the Strategic Advisory Group of Experts on Immunization],” the researchers wrote. “Additionally, our study provides detailed information on the effect of IPV and bOPV in inducing type 2 intestinal immunity — an issue of essential public health importance for better understanding of polio transmission, as we prepare for the global introduction of IPV and switch to bOPV.” – by Jen Byrne
Disclosure: The researchers report no relevant financial disclosures.