Ottawa's top doctor says parents can move up their child's second dose of the COVID-19 vaccine as the Omicron variant spreads and students prepare to return to school for in-person learning.

The National Advisory Committee on Immunization recommended children between the ages of 5 and 11 receive the second dose eight weeks after the first dose.

Medical officer of health Dr. Vera Etches says while the NACI recommendation points to evidence showing that an eight-week interval produces a "stronger and longer-lasting immune response," parents can move up the dose to as early as 21 days after the first.

"A shorter interval of no less than 21 days has been shown to be safe and effective. So parents who wish to book their child at a shorter interval have the option to do so," said Etches, noting parents must provide "informed consent" to move up the second dose.

Health Canada approved the Pfizer-BioNTech Comirnaty COVID-19 vaccine for children 5 to 11 years of age in November with a three-week interval between doses.

Parents and guardians can call the provincial booking line at 1-833-943-3900 to book a second dose appointment, or drop-in to an Ottawa Public Health community clinic.

Etches says Ottawa Public Health is working to increase vaccination rates among students, teachers and school staff, including school-based immunization clinics once schools reopen.

As of Wednesday, 64 per cent of Ottawa children aged 5 to 11 had received one dose of the COVID-19 vaccine, while eight per cent had received two doses.