Key result
The switch from trivalent to bivalent oral poliovirus vaccine was associated with a significant decrease in type 2 poliovirus seroprevalence from 91.6% to 67.4%.
Why the study?
China switched from trivalent oral poliovirus vaccine to bivalent oral poliovirus vaccine with 1 dose of inactivated vaccine in 2016, prompting assessment of the switch's impact on poliovirus immunity, particularly type 2.
Does the switch from trivalent to bivalent oral poliovirus vaccine reduce immunity against poliovirus type 2 in children?
Cross-Sectional (n=172)
Yes
Does the switch from trivalent to bivalent oral poliovirus vaccine reduce immunity against poliovirus type 2 in children?
Absolute Event Rate: 67.4% vs 91.6%
The switch from trivalent to bivalent oral poliovirus vaccine significantly reduces immunity against type 2 poliovirus, highlighting a high risk for type 2 vaccine-derived poliovirus emergence.
Decreased type 2 seroprevalence after bOPV switch signals potential immunity gap; cross-sectional data leaves open causal effects on population immunity.
BACKGROUND: China implemented the globally synchronized switch from trivalent oral poliovirus vaccine (tOPV) to bivalent OPV (bOPV) and introduced 1 dose of inactivated poliovirus vaccine on 1 May 2016. We assessed the impact of the switch on the immunity level against poliovirus, especially type 2. METHODS: Children born between 2014 and 2017, who were brought to the hospitals in Urumqi city, Xinjiang Province in 2017, were enrolled and blood samples were collected to test for antibody titers against poliovirus. A comparison of seroprevalence between the children born before (preswitch group) and after the switch (postswitch group) was performed to assess the impact of the switch on the immunity level against polio. RESULTS: A total of 172 subjects were enrolled. The overall seroprevalences were 98.8%, 79.1%, and 98.3% for types 1, 2, and 3, respectively. Seroprevalence for type 2 significantly decreased from 91.6% in the preswitch group to 67.4% in the postswitch group, but no statistically significant change was observed for both types 1 and 3. CONCLUSIONS: The switch from tOPV to bOPV can provide high-level immunity against types 1 and 3 but not against type 2, indicating a high risk of type 2 vaccine-derived poliovirus emergence and transmission.
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Yan et al. (2020) conducted a cross-sectional in Poliovirus immunity (n=172). Switch from trivalent to bivalent oral poliovirus vaccine (postswitch group) vs. Preswitch group (trivalent oral poliovirus vaccine) was evaluated on Seroprevalence for type 2 poliovirus. The switch from trivalent to bivalent oral poliovirus vaccine was associated with a significant decrease in type 2 poliovirus seroprevalence from 91.6% to 67.4%.
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