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MLHU Extending Shorter Second Dose Interval Option to Those Who Got Their First Dose On or Before May 9th

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*PLEASE NOTE: A clarification for this public service announcement has been made and can be read here.

With 17,000 doses of Moderna vaccine expected to arrive early next week, and a similar amount the following week, the Middlesex-London Health Unit (MLHU) is extending second dose appointment re-booking to anyone who got their first dose on or before May 9th. The added deliveries of Moderna vaccine are above and beyond the regular deliveries of Pfizer vaccine the Health Unit receives, allowing shorter second dose intervals for a much larger group starting tomorrow, Wednesday, June 16th at 8:00 a.m.

The additional vaccine that will arrive over the next two weeks will allow the Health Unit to expand and improve the efficiency of its vaccine rollout program, making it possible for people to complete their COVID-19 vaccination series more quickly. The Public Health Agency of Canada and the National Advisory Committee on Immunization (NACI) have authorized the use of either the Pfizer BioNTtech or Moderna vaccine as a second dose when either mRNA vaccine, or the Oxford AstraZeneca vaccine, was given as the first dose. This principle of vaccine interchangeability is an important component of the MLHU effort to deliver more vaccine to more people, more quickly.

While second doses of COVID-19 vaccine can now be delivered as short as eight weeks apart, it is important to note that a 12-week interval between doses provides better protection in the long term. However, the accelerated second dose schedule is recommended as it is required to protect against the Delta variant, which will soon be the dominant COVID-19 variant in Ontario.

How to book a new second-dose appointment, starting Wednesday morning:

  • Book online at (new appointments open daily at 8:00 a.m.)
    • For those vaccinated on or before May 9th who need to re-schedule a shorter-interval second dose appointment, enter Gate #4 I need to re-book my scheduled second dose.
    • For individuals who received their first dose in another setting or out of region and need to book a second dose within four weeks of their first dose, enter Gate #5, I received my first dose elsewhere and now need to book a second dose.
  • Call 226-289-3560 (8:00 a.m. to 7:30 p.m., Monday to Sunday)

The MLHU is also reminding those who used the same email address or cell phone number to book first dose times for more than one person that they can now re-book second dose appointments at; select Gate #4, (I need to re-book my scheduled second dose), and select Option 2.

For more information about COVID-19 vaccine and what to expect on the day of your vaccine appointment, visit:

Media Contact:
Dan Flaherty, Communications Manager, Middlesex-London Health Unit,
519-663-5317 ext. 2469 or 519-617-0570 (cell.)

Dr. Chris Mackie, Medical Officer of Health, Middlesex-London Health Unit


Tags: COVID-19, Vaccine