Immune persistence after different polio sequential immunization schedules in Chinese infants

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• Global polio eradication efforts transitioned from trivalent oral poliovirus vaccine (tOPV) to inactivated poliovirus vaccine (IPV) and bivalent OPV (bOPV) in 2016.
• Limited data exist on the long-term immune persistence of current sequential polio vaccination schedules.

Purpose of the Study:

• To evaluate the immune persistence of different sequential inactivated poliovirus vaccine (IPV) and bivalent oral poliovirus vaccine (bOPV) immunization schedules.
• To assess poliovirus-specific antibody titers and positive rates over time in children.

Main Methods:

• Analysis of serum samples from 1104 participants in phase III clinical trials at 24, 36, and 48 months of age.
• Determination of serum neutralizing antibody titers against poliovirus types 1, 2, and 3.
• Evaluation of poliovirus-specific antibody-positive rates for different sequential immunization regimens.

Main Results:

• No significant differences in poliovirus types 1 and 3 antibody-positive rates were observed across groups at 24, 36, or 48 months.
• The IPV-IPV-tOPV schedule demonstrated nearly 100% poliovirus type 2 antibody-positive rates, significantly higher than other groups.
• Schedules with one or two IPV doses followed by bOPV showed reduced persistence of poliovirus type 2-specific antibodies.

Conclusions:

• Sequential IPV and bOPV schedules may not adequately maintain long-term immunity against poliovirus type 2.
• The IPV-IPV-tOPV schedule appears superior in maintaining humoral immunity across all three poliovirus serotypes.
• Further research is needed to optimize polio vaccination strategies for sustained population immunity.