Publication date: Oct 12, 2024

This study aimed to assess the long-term persistence of neutralising antibodies (nAb) titres and seroprotection proportions after the 4 and 5 doses of inactivated polio vaccine (IPV). Serum samples from 299 children in Hong Kong were collected and used to estimate the persistence of nAb titres and seroprotection proportions by neutralisation test. The mean nAb titres against polioviruses type 1, 2 and 3 (PV1, PV2 and PV3) one month after receiving the 4 dose of IPV at 19 months of age were 2,068 (95% credible interval: 1,517 – 2,864), 4,705 (3,439 – 6,436) and 2,758 (1,894 – 4,086), but declined substantially in 4 years to 268 (222 – 325), 751 (630 – 900), and 411 (323 – 521), respectively. Administration of the 5 dose of IPV restored nAb titres among children aged 6-7 years, and the decline in nAb titres was slightly slower with the estimated mean titres of 355 (272 – 462), 538 (427 – 681), and 548 (378 – 786) against PV1, PV2, and PV3 at 4 years post the 5 dose. We estimated that the proportion of children who were seroprotected against PV1, PV2 and PV3 would drop below 90% at: (i) 8. 2, 10. 8, 8. 7 years after the 4 dose; and (ii) 11. 6, 11. 2, 11. 0 years after the 5 dose. The results revealed the immuno-persistence after the 4th and 5th dose of IPV and highlighted the importance of completing immunization series to ensure high vaccination coverage, particularly among children in the developing countries affected by the COVID-19 pandemic.

Semantics

Original Article