TORONTO -- No matter how successful vaccination campaigns are it's unlikely Canada will achieve herd immunity without immunizing children, especially as a return to school means they will gather together in the fall, physicians say.

And though almost four in five eligible people across Ontario have received at least one vaccine, the picture looks a lot less positive when those figures include children, who won’t be able to get a shot for months.

"Children are as efficient as adults when it comes to the spread of the Delta variant," Dr. Iris Gorfinkel, a family physician and researcher, told CTV News Toronto. "They are a critical part of the population to get vaccinated."

The spread of the Delta variant is a big concern for parents looking at returning children under 12 to school, said Lindsay Siple, whose three children under twelve will be heading back after the summer.

"You have a big group of kids who are under 12, who are not yet eligible to get vaccines, especially with the Delta variant that’s coming in, I’m nervous about what the numbers are looking like and whether we’re setting ourselves up for another shutdown," Siple said.

One of her daughters, Elise, said she is hoping that social distancing measures and masks will work when she returns to Grade four.

"I'm very excited to see all my friends," she said. "I think if everybody follows the rules the numbers won’t go very high."

Provincial figures show 79.6 per cent of Ontario’s population 12 and over have received at least one dose of a vaccine. That drops to 69.9 per cent when children are included. 

There are similar figures in Toronto, with 79.9 per cent of people over 12 who have at least one dose, and 71.0 per cent when children are included.

The goal of herd immunity, where outbreaks don’t spread because enough people are immune to the disease, is about 90 per cent, Gorfinkel said.

"Do the math. If 12 per cent of the population is under 12, that means 88 per cent is the best we can do if everybody got vaccinated. In other words, we cannot achieve herd immunity without vaccinating the children," she said.

Including those areas, the vaccine coverage map looks bleaker, with multiple areas in the GTA where more than one in three people have not received any shots.

That’s the situation in some 17 postal code zones in Toronto, nine in Hamilton, six in Peel region, and six in Durham region. 

By that measure, Thorncliffe Park for example has four in ten people without any vaccines at all, despite months of targeting the area as a hot spot, because officials say it’s “home to a large number of youth under 12 years old who are not eligible for the COVID-19 vaccine in Canada.”

The effect of the vaccine on younger people is being examined now, with preliminary data expected for ages five to 11 in the fall, and for under five years old in the winter.

Canada’s Health Minister, Patty Hajdu, said this week that Health Canada will review the data when it arrives.

“Until they submit the approval, we know our children are unprotected. And children can get COVID-19. Children can get very sick. And I don’t think anyone wants to see their child struggle in a hospital bed, or have to stay home, or god forbid have an outbreak in a community that requires school closures,” Hajdu said.