More than half of Waterloo Region children between five and 11 years old have not received a first dose of the COVID-19 vaccine.

Regional officials said there are thousands of appointments available for kids and they're increasing their efforts to encourage people to vaccinate their children.

As of Thursday morning, 45.44 per cent of eligible children have received one dose.

Health officials said there has been a significant slow down in demand for kids' shots.

"This seems to be a phenomenon seen in other areas of the province as well," Medical Officer of Health Dr. Hsiu-Li Wang said at a Board of Health meeting earlier this week. "There's an initial group of parents who are very keen to have their five to 11-year-old vaccinated, but then after that, there was quite a slow down, so the uptake on that is a lot slower."

As of Tuesday, there were almost 10,000 appointments available for pediatric vaccines at the Boardwalk and Pinebush clinics.

Officials with the region's vaccine task force said there are several factors behind the slow in demand.

"I think the hesitation for parents comes from that messaging that COVID is relatively mild in children, and I think with Omicron that's even more true, where even adults are experiencing milder symptoms," said David Aoki, director of infectious diseases. "But, our goal is to prevent transmission and infection altogether, so that visiting grandparents and other people who may be immunocompromised are protected from that herd immunity."

In Wellington-Dufferin-Guelph, 47.5 per cent of eligible children have received a first dose. That public health unit announced Wednesday that children can drop in for a vaccine without an appointment.