OTTAWA, Nov 12 (Reuters) - Canada"s COVID-19 cases are creeping higher as cold weather approaches, health officials said on Friday, and more restrictive public health measures may be needed if cases continue to climb. The seven-day average for new cases nationally is 2,500, 11% higher than last week, Chief Medical Officer Theresa Tam said. Children under 12, who cannot yet be vaccinated, are contracting COVID-19 more than all other age groups, she said. However, a review of Pfizer/BioNTech"s (PFE.N), (22UAy.DE) COVID-19 vaccine for children aged 5 to 11 years should be completed in one to two weeks, said another official, a sign inoculations for children could start this year. Deputy chief medical officer Howard Njoo said it was important to not ease public health measures too quickly, especially as more people will spend time indoors - where contagion is more likely - in the winter. "The country must be ready to reinstate public health measures if required due to a rise in coronavirus cases," Njoo added. Earlier this week, Ontario, Canada"s most populous province, pushed back its plan to lift restrictions next week on the number of people who can congregate in restaurants, bars and other such "high-risk settings". read more The Sudbury health region in Ontario, about 250 miles (400 km) north of Toronto, has tightened restrictions, while the Yukon territory in north-east Canada declared a state of emergency after announcing 80 COVID-19 cases in three days. read more