KITCHENER -- People living in Waterloo Region or Wellington-Dufferin-Guelph who received an mRNA vaccine on or before May 30 are now eligible to book an accelerated second dose appointment.

Both communities were identified as Delta variant hot spots by the province earlier this month.

Waterloo Region also launched a new self-serve vaccine booking system on Wednesday, which no longer requires people to pre-register for a COVID-19 vaccine.

Residents can also reschedule their second dose using that system.

Health officials continue to encourage people to take the first vaccine available to them, adding that Moderna and Pfizer can be mixed for first and second doses.

Vaccines are also available at pharmacies and physicians in the region. Appointments should be booked directly through the care providers.

Toronto, Peel, Halton, Porcupine, York, Hamilton, Simcoe-Muskoka and Durham are also listed as Delta variant hot spots.

On Wednesday, Huron Perth Public Health announced it is also expanding second-dose vaccine eligibility.

As of June 23, anyone who received an mRNA vaccine on or before May 30 is eligible to book a second dose appointment at Huron-Perth vaccine clinics at a shortened interval.

“Being fully vaccinated is very important. Two doses of vaccine – whether the same product or a mix of two vaccine products – provides safe and highly effective protection against the COVID-19 virus and variants, including the highly transmissible Delta variant,” Dr. Miriam Klassen, Medical Officer of Health for Huron Perth, said in a release. “I strongly encourage everyone to get their vaccine as soon as possible, and to make their second dose a priority once they are eligible. The more people who are fully vaccinated, the less chance of COVID-19 spreading in our communities.”

Although Huron-Perth has not be designated a Delta variant hot spot, officials say an "increased COVID-19 vaccine supply" has allowed the health unit to speed up second dose appointments.

Appointments can be booked online or by calling 1-833-753-2098.

The health unit says all of its vaccine clinics indicate which vaccine, Pfizer or Moderna, will be administered. However, supply changes mean the health unit cannot guarantee the availability of a specific vaccine.

Officials stressed that Pfizer and Moderna are interchangeable mRNA vaccines.

Anyone who rebooks an appointment is urged to cancel their original booking.