Analysis on the characteristics of delayed EV71 vaccination among children in the birth cohort from 2017 to 2022

To analyze the changes in the proportion of Human enterovirus 71 (EV71) vaccination among children born in the 2017-2022 cohort, understand the delay of the first dose of EV71 vaccination in Suzhou, and explore the seasonal distribution and influencing factors of EV71 vaccination among children born in the 2017-2022 cohort. Personal information and EV71 vaccination information of registered children born between January 1, 2017 and December 31, 2022 in Suzhou were collected through the children module of Jiangsu Province Immunization Service Management Information System. The quantitative characteristics and influencing factors were analyzed by ecological research and descriptive epidemiology. The proportion of children born during 2017-2022 who received at least one-dose EV71 vaccination ranged from 21.9% to 32.5%, and full course of EV71 vaccination proportion ranged from 20.6% to 32.1%. In addition, with the exception of the 2017 birth cohort, the number of EV71 vaccination in the 2018-2022 birth cohort reached its peak at 11 months of age. There were 10,497 children (5.0%) who received the first dose at 6 months of age (recommended starting month), and 98,918 children (47.1%) who received the first dose at 7 to 12 months of age. The extended duration M (<i>P</i>₂₅, <i>P</i>₇₅) was 70 (27, 102) days. Regarding the recommended vaccination season, the distribution of inoculation season was not consistent with the actual season, and most of them were delayed by one season. Summer and autumn seasons were associated with timely vaccination, while the winter was the main delay season. The overall EV71 vaccination proportion among children born in Suzhou from 2017 to 2022 was low, but among those who initiated vaccination, completion of the two-dose schedule was high. The timeliness of the first EV71 vaccination was poor and associated by the seasons. Emphasize the dissemination of knowledge about seasonal associations of EV71 to enhance confidence in EV71 vaccination.