It's a precaution to monitor for any side effects from the COVID-19 vaccine, the government said.
"This means that when your child receives their COVID-19 vaccine, they will not be given other vaccines at the same time," it said.
Some parents whom CBC spoke to said that when they made vaccine appointments through Ontario's booking portal, there was no information indicating five-to-11-year-olds should wait two weeks between a flu shot and a COVID-19 vaccine.
Klassen said she'd also booked a COVID-19 vaccination for her this weekend, without being aware of the guidance from public health.
Doug Wilkinson said he and his wife waited to book their 11-year-old daughter Mabel's flu shot, knowing they would then face a two-week wait for a COVID-19 vaccination.