Sabin Strain Polio Vaccine Noninferior to Conventional Vaccine

According to data published in The Journal of Infectious Diseases, the Sabin strain-based inactivated polio vaccine demonstrated an immunogenicity profile noninferior to that of the conventional inactivated polio vaccine, and also demonstrated a good safety profile.

Using a randomized controlled double-blinded noninferiority trial, the immunogenicity and safety of the Sabin strain-based inactivated polio vaccine was assessed. A  total of 3 cohorts of healthy infants age 60 to 90 days were randomly assigned to receive 1, 2, or 3 doses of either the Sabin strain-based inactivated polio vaccine (n= 599, 585, and 578 patients, respectively) or the conventional inactivated polio vaccine (n= 600, 592, and 589 patients, respectively).

Rates of seroconversion in the 2 groups were 98.0% for the Sabin strain-based inactivated polio vaccine and 94.1% in the conventional inactivated polio vaccine group, for type 1 poliovirus (P <.01). The rate for type 2 poliovirus was 94.8% and 84.0%, for the Sabin vaccine and the conventional vaccine, respectively, (P <.01) and 98.9% and 97.7%, respectively, for type 3 poliovirus (P =.11). Of note, in participants who were seronegative before vaccination, there was a 100% seroconversion rate against all 3 types of polioviruses in the 2 groups. Researchers also adjusted for maternal antibody influence on the immunogenicity of the vaccines and found that seroconversion rate against type 1 poliovirus was 99.5%, and 99.3% for the Sabin and conventional vaccines, respectively; 98.6% and 97.0% against type 2 poliovirus for the Sabin and conventional vaccine, respectively; and for type 3 poliovirus the adjusted seroconversion rate was 99.6% for both vaccines.

For the purposes of safety assessment, 599 of the Sabin strain-based inactivated polio vaccine and 600 of the conventional inactivated polio vaccine participants were included in the safety population. Of participants who received the Sabin vaccine, 398 participants and 340 of those who received the conventional vaccine developed an adverse event. Most adverse events were classified as minor; grade 3 adverse events occurred in 0.5% and 1.5% of participants who received the Sabin vaccine and the conventional vaccine, respectively. Fever was the most common adverse event, occurring in 61.6% of participants who received the Sabin vaccine and 49.8% of participants who received the conventional vaccine (P <.01).

The study investigators noted 2 study limitations. The first was that the strains used to measure the neutralizing antibodies induced by the 2 vaccines in which the Sabin strains from which the Sabin strain-based inactivated polio vaccine was generated may have resulted in bias regarding the measured greater increase in geometric mean titers induced by the Sabin strain-based inactivated polio vaccine may be biased. Second, it is possible that the immunogenicity of the Sabin strain-based inactivated polio vaccine was underestimated because some participants may have received maternal antibodies before vaccination. Analyses adjusted for maternal antibodies did provide evidence for this potential underestimation.

The data revealed that the Sabin strain-based inactivated polio vaccine studied demonstrated an immunogenicity profile noninferior to that of the conventional IPV and had a good safety profile. Researchers also concluded that, “the launch of the studied [Sabin strain-based inactivated polio vaccine] may contribute to the polio eradication endgame in developing countries and the sustainment of a polio-free world.”

Reference

Hu Y, Wang J, Zeng G, et al. Immunogenicity and safety of a Sabin strain-based inactivated polio vaccine: A phase 3 clinical trial [published online April 8 2019]. J Infect Dis. doi:10.1093/infdis/jiy736