Surveillance of immunity acquired from poliovirus immunization including vaccination with the Sabin strain-derived inactivated vaccine

Abstract

In Japan, routine immunization for polio using the oral polio vaccine (OPV) was suspended in September 2012; subsequently, an immunization program with inactivated polio vaccines (IPVs), the conventional IPV (cIPV) derived from virulent strains, and IPV derived from Sabin strains (sIPV), was introduced. However, the immunity induced by sIPV is not well characterized. This study assessed and compared neutralizing antibodies produced against poliovirus in cases who received doses of OPV or IPV. Serum samples (n = 1186) were collected yearly between 2013 and 2016 as part of the National Epidemiological Surveillance of Vaccine-Preventable Disease. The neutralizing antibody titers for Sabin strain types 1, 2, and 3 in 224 children, aged between 0 and 90 months, were assessed. Seropositive rates after vaccination with OPV or IPV were more than 90%. Neutralizing antibody titers for Sabin type 1 after vaccination with IPV were lower than those with OPV, while those for Sabin types 2 and 3 after vaccination with IPV were significantly higher than those with OPV. Analyses of antibody titer dynamics revealed that the decay of antibody titers for Sabin types 1, 2, and 3 in cases vaccinated with IPV was steeper than those with OPV. Thus, our study showed that although IPV induced a sufficient level of neutralizing antibody, the immunity induced by IPV was not maintained as long as that by OPV. Our study suggested that a long-term survey should be conducted for polio vaccination using IPV and that it might be necessary to consider booster vaccination for IPVs.

Keywords: Poliovirus; Sabin strains; inactivated vaccine; neutralizing antibody; seropositive rates.

Figure 1.

Seropositive rates (a) and geometric mean antibody titers (GMTs) (b) of cases vaccinated with Sabin type 1, 2, and 3. Seropositive rates and GMTs were plotted by age and age groups. Seropositivity was represented for titers of 1:8 or more. Age and age groups were plotted for age groups between 0 to 9 years and for every 10 years thereafter. Type 1: Sabin type 1; Type 2: Sabin type 2; Type 3: Sabin type 3.

Figure 2.

Regression line of neutralizing antibody titers induced by vaccination with two doses of oral polio vaccine (OPV), four doses of inactivated polio vaccine (IPV), or four doses of Sabin strain-derived inactivated polio vaccine (sIPV). The relationship between neutralizing antibody titers and elapsed time after the vaccination schedule completion was depicted by least-squares curve-fitting method. p values less than 0.05 were considered significant. Each regression line was statistically significant. There were significant differences (p < 0.05) between regression slopes of two doses of OPV and those of four doses of IPV for Sabin types 1, 2, and 3. In addition, regression slopes of two doses of OPV and those of four doses of sIPV for Sabin type 3 were significantly different (p < 0.05). Circle: two doses of OPV; open circle: four doses of IPV; open square: four doses of sIPV; dotted line: regression line of two doses of OPV; alternate long and short dashed line: regression line of four doses of IPV; dashed line: regression line of four doses of sIPV. Regression line of two doses of OPV for Sabin type 1; y = −0.0284x + 8.8741 R² = 0.0917, Sabin type 2; y = −0.0298x + 8.1965 R² = 0.0917, Sabin type 3; y = −0.0435x + 6.092 R² = 0.1052. Regression line of four doses of IPV for Sabin type 1; y = −0.1263x + 8.7408 R² = 0.3972, Sabin type 2; y = −0.0917x + 9.5512 R² = 0.331, Sabin type 3; y = −0.1196x + 8.9806 R² = 0.3445. Regression line of four doses of sIPV for Sabin type 1; y = −0.0789x + 8.1942 R² = 0.1848, Sabin type 2; y = −0.0568x + 9.0626 R² = 0.2078, Sabin type 3; y = −0.1234x + 9.3093 R² = 0.4052.