The hospital confirmed 281 new cases last week, up more than 200 from the prior week.
The positivity rate also climbed from 7% recorded the week of December 27 to more than 19.2% last week.
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Consistent with national trends, Valley Children's data reflects a significant spike in positive cases and hospitalizations of children after the holidays and expects it to climb throughout January.
Hospital officials urged everyone five years and older to receive the COVID-19 vaccine.