WATERLOO -- Waterloo Region residents who received an AstraZeneca vaccine as their first dose will be able to choose between getting another jab of the same vaccine or switching to an mRNA vaccine as of Friday.

The move comes as the province outlined two options for AstraZeneca recipients in line with updated guidance from the National Advisory Committee on Immunization (NACI), the health unit said in a release Thursday.

NACI recently authorized for a first dose of AstraZeneca to be followed by either a Pfizer or Moderna vaccine. Both second-dose options will be provided at the recommended 12-week interval.

The Waterloo health unit says AstraZeneca is available at participating pharmacies and some primary care offices. Residents are advised to get their second dose at the same location where they received their first.

Individuals who received AstraZeneca as a first dose and wish to switch to Pfizer or Moderna for their second should contact the pharmacy where they received their initial jab.

Many pharmacies are now offering Pfizer or Moderna vaccines and will be able to schedule second-dose appointments, Region of Waterloo public health said.

Second-dose appointments can also be booked at a Waterloo Region vaccination clinic by emailing phecovidimms@regionofwaterloo.ca or by calling the Service First Call Centre at 519-514-1499.

The health unit is reminding residents that all first and second doses are recorded in a provincial database, adding staff at all clinic locations can very first-dose type and date given prior to administering the second dose.

Anyone who changes the location for their second-dose appointment is urged to cancel their original booking.