Cross-neutralization Capacity of Immune Serum from Different Dosage of Sabin Inactivated Poliovirus Vaccine Immunization against Multiple Individual Polioviruses

Immune Persistence following Primary Immunization and the Immunogenicity and Safety of a Booster Dose of a Multidose Sabin Strain-Based Inactivated Polio Vaccine in Infants Aged 18 Months

BACKGROUND

The multidose Sabin-strain inactivated poliovirus vaccine (sIPV) has the potential to significantly aid in the eradication of poliomyelitis, particularly in low- and middle-income countries. As part of a phase III clinical trial in which infants were given three doses of primary immunization at 2, 3, and 4 months of age, this study aimed to evaluate immune persistence following primary immunization, as well as the safety and immunogenicity of a booster of the 5-dose sIPV in infants aged 18 months.

METHODS

Infants aged 18 months were given one booster dose of 5-dose sIPV in stage one, which was open-label. Unblinding was performed for stage two after completing primary immunization, which was randomized, blinded, and controlled; infants aged 18 months in the test group I-III, IPV group, and single-dose sIPV group were given one booster dose of 5-dose sIPV, conventional IPV, and single-dose sIPV, respectively, in stage two.

RESULTS

This study included 1438 infants in the immune persistence and safety set and 1387 infants in the booster per-protocol set. Fourteen months after primary immunization, the seropositivity rates (≥1:8) for types 1-3 were 100%, 99.88%, and 99.53% in the 5-dose sIPV groups; 100%, 98.97%, and 97.23% in the IPV group; and 99.66%, 100%, and 99.66% in the single-dose sIPV group. A total of 30 days after booster immunization, the seropositivity rates (≥1:8) of 3 serotypes in all the groups reached 100%. The geometric mean titers of neutralizing antibodies for types 1-3 in the 5-dose sIPV group were 9962.89, 10273, and 7870.21, with geometric mean increases of 15.76, 33.15, and 24.5, compared to the pre-booster level. The overall incidence of adverse reactions was 8.97%, with fever being the most common, observed at rates of 7.1%, 5.52%, and 7.96% in the 5-dose sIPV, IPV, and single-dose groups, respectively (p = 0.4845).

CONCLUSIONS

The 5-dose sIPV has shown promising immune persistence and robust immune response following a booster immunization, coupled with an acceptable safety profile.

Immunogenicity and immune persistence in 4-year-old children completing four doses of Sabin strain or wild strain inactivated poliovirus vaccine: A phase IV, open-labeled, parallel-controlled observational study

BACKGROUND

Sabin strain inactivated poliovirus vaccine (hereinafter as "sIPV") has been marketed globally in recent years, and more data on its immune persistence are needed.

METHODS

This is a phase IV, open-labeled, parallel-controlled observational study based on phase III clinical trial as required by the China National Medical Products Administration (NMPA). At least 450 subjects aged four years (48-54 months) who received four doses at 2, 3, 4 and 18 months of age of sIPV or wild strain poliovirus vaccine (wIPV) in phase III clinical trial enrolled at a 2:1 ratio and collected blood samples for neutralizing antibody testing.

RESULTS

A total of 500 subjects of four years old (334 in the sIPV group and 166 in wIPV group) were finally enrolled. The seropositivity rates (≥1:8) of neutralizing antibodies against serotype I-III were all 100.00% in all participants, and the geometric mean titers (GMT) were 1117.33 vs. 337.77 against serotype I, 632.72 vs. 267.34 against serotype Ⅱ, 1665.98 vs. 923.02 against serotype III in the sIPV group and wIPV group respectively at 4 years old. The seropositivity rates and GMTs of neutralizing antibodies in the test group were non-inferior to that of the control group against all three serotypes at different time points (P < 0.0001). The antibody GMT experienced a 10-fold, 8-fold, and 7-fold decline for serotypes I, Ⅱ, and III in the sIPV group, and a 13-fold, 7-fold, and 7-fold decline in the wIPV group from one month after booster vaccination to 4 years old.

CONCLUSIONS

The neutralizing antibody level is much higher than the seroprotection cutoff (≥1:8) among children of 4 years old who completed the four-dose vaccination of either sIPV or wIPV. Therefore, another booster vaccination is not recommended at 4 years old. Longer immune persistence observation is still ongoing.

REGISTRATION

ClinicalTrials.gov Identifier: NCT04989231.

Safety, immunogenicity, and lot-to-lot consistency of a multidose Sabin strain-based inactivated polio vaccine: a phase III, randomized, blinded, positive-control clinical trial in infants aged 2 months

OBJECTIVES

To evaluate the safety, immunogenicity, and lot-to-lot consistency of Sabin strain-based inactivated polio vaccine (sIPV) in a five-dose vial presentation.

METHODS

Stage I was an open-label safety observation, in which 72 healthy subjects (including 24 adults, children, and infants each) were given one or three doses of the five-dose vial sIPV; stage II was a randomized, blinded, and positive-control study, in which 1500 infants were randomized at the ratio of 1: 1: 1: 1: 1 into five groups to receive either three doses of the five-dose sIPV three lots, a conventional inactivated poliovirus vaccine, or a single-dose sIPV as controls, for primary immunization. Safety, immunogenicity, and lot-to-lot consistency were assessed.

RESULTS

Among 1456 subjects who completed the primary immunization, the geometric mean titer ratios of types 1, 2, and 3 of each pair of lots were all within the equivalence criteria margin (0.67-1.50). The seroconversion rates of types 1, 2, and 3 in the combined test group were 98.02%, 94.07%, and 98.77%, respectively, which were noninferior to both control groups. The overall incidence of adverse reactions was 29.68% and erythema was the most common adverse reaction with incidences of 10.47%,9.33%, and 9.73% in the combined test group and control groups (P >0.05).

CONCLUSION

The five-dose sIPV demonstrated good safety, immunogenicity, and lot-to-lot consistency.

Safety, Immunogenicity and Lot-to-Lot Consistency of Sabin-Strain Inactivated Poliovirus Vaccine in 2-Month-Old Infants: A Double-Blind, Randomized Phase III Trial

Background: The Sabin-strain-based inactivated poliovirus vaccine (sIPV) plays an important role in poliomyelitis eradication in developing countries. As part of the phase III clinical development program, this study aimed to evaluate the safety, immunogenicity and lot-to-lot consistency of the sIPV in 2-month-old infants. Method: We conducted a phase III, randomized, double-blind, positive-controlled trial in which 1300 healthy infants were randomly assigned to four groups in a 1:1:1:1 ratio to receive one of the three lots of the sIPV or the control IPV at 2, 3 and 4 months of age. Serum samples were collected before the first dose and 30 days after the third dose of vaccination to assess the immunogenicity. Solicited local and systemic reactions were recorded within 7 days and unsolicited adverse events within 30 days after each vaccination. Results: Of the 1300 randomized infants, 1190 infants completed the study and were included in the per-protocol population. The seroconversion rates in the three lots of the sIPV were 95.67%, 97.03% and 95.59%, respectively, for type 1; 94.33%, 93.73% and 92.88%, respectively, for type 2; and 98.67%, 99.67% and 99.32%, respectively, for type 3. The ratios of GMTs for poliovirus types 1, 2 and 3 of each pair of lots were all between 0.67 and 1.50, therefore meeting the predefined immunological equivalence criteria. For the seroconversion rate of poliovirus types 1, 2 and 3, the pooled sIPV group was non-inferior to the IPV group. The incidence of solicited and unsolicited adverse reactions (ARs) was similar in the pooled sIPV lots and the IPV group, and most of them were mild to moderate in severity. Non-vaccine-related serious adverse events (SAEs) were reported. Conclusions: Three consecutive lots of sIPV demonstrated robust and consistent immunogenicity. The safety and tolerability of the sIPV was acceptable and similar to that of the IPV.