KITCHENER -- Vaccine clinics in Wellington-Dufferin-Guelph will be administering Moderna this week following a supply shortage of Pfizer vaccines.

In a news release, officials said they're prioritizing Moderna for adults aged 18 and older.

“These shipment changes are certainly challenging,” WDG Medical Officer of Health Dr. Nicola Mercer said in a news release. “We are doing everything we can to minimize the impact on the public, but we must do what we can to ensure we continue to vaccinate our region as quickly as possible. I want to assure residents of Wellington-Dufferin-Guelph that their first or second dose will be safe and effective.”

Pfizer vaccines will be saved for youth aged 12 to 17, since that vaccine is the only one approved in Canada for that age group.

Public health officials said the vaccines are safe to mix and provide strong protection against COVID-19. They are both mRNA vaccines.

Waterloo Region clinics will also administer Moderna this week due to the Pfizer shortage.