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The EnCORE study is a prospective serology study of SARS‐CoV‐2 in a cohort of children from Montreal, Canada. Based on data from our fourth round of data collection (May–October 2022), we estimated SARS‐CoV‐2 seroprevalence and seroconversion. Using multivariable regression, we identified factors associated with seroconversion. Our results show that previously seronegative children were approximately 9–12 times more likely to seroconvert during the early Omicron‐dominant period compared to pre‐Omicron rounds. Unlike the pre‐Omicron rounds, the adjusted rate of seroconversion among 2‐ to 4‐year‐olds was higher than older age groups. As seen previously, higher seroconversion rates were associated with ethnic/racial minority status.