Mixing COVID vaccines: Here’s what Hamilton doctors say you need to know
Adults going to Hamilton's COVID mass vaccination clinics will likely get Moderna as the city saves low supplies of Pfizer for youth.
Halton Region also switched to Moderna at all of its clinics Monday due to an unexpected delay in federal Pfizer shipments.
We would ask that you not reschedule any appointments to try and get a second dose of Pfizer at a later date," said Ontario's chief medical officer of health, Dr. David Williams. Mixing vaccines is effective and safe and enables Ontarians to receive their dose sooner."
The Pfizer shortfall this week comes as the province received unprecedented amounts of Moderna. Hamilton got an extra 6,300 doses more than normal because it has been declared a Delta hot spot.
Get the first vaccine that's offered," said Dr. Zain Chagla, co-medical director of infection control at St. Joseph's Healthcare. Getting to normal means much more than anything else right now."
If people walk away from Moderna, obviously that concerns everybody," said Dr. Dirk Huyer, co-ordinator of provincial outbreak response, while emphasizing two shots is key to protecting Ontario from a fourth wave.
The province is in a race between vaccination and the fast-spreading Delta variant, which is soon expected to be the dominant strain.
Hamilton added almost 40,000 appointments to the provincial portal for June 18 to 21. Another 35,000 more started to go online Monday as those who got a first shot of Moderna or Pfizer on or before May 9 became eligible.
More can book Wednesday as it opens up to those who got Moderna and Pfizer on or before May 30 in Delta hot spots like Hamilton and Halton.
However, it's only a head start of about five days as all Ontarians 18 and older become eligible to book an early second dose the week of June 28.
Those booking in Hamilton are currently told, You will receive an mRNA vaccine (either Moderna or Pfizer) at the clinic depending on supplies and age eligibility."
Adults can get either vaccine, while youth age 12 to 17 can only have Pfizer.
The National Advisory Committee on Immunization (NACI) recommends that you get the same mRNA vaccine as your first shot unless it is not readily available," in which case Moderna and Pfizer can be considered interchangeable."
The province went one step further on Thursday telling Ontarians to take the first mRNA vaccine offered to them as Ontario tries to curb the spread of Delta.
Mixing vaccines is safe," said Chagla. We boost ourselves with different brands of vaccines every year - like the flu shot or tetanus booster."
He compares mixing mRNA vaccines to the difference between Coke and Pepsi or two different brands of over-the-counter Tylenol. Your body can't tell the difference between Moderna and Pfizer, and responds to the vaccine to trigger an immune response regardless."
The urgency for second doses is because it significantly ups protection against Delta - also known as B.1.617.2 - which is about 60 per cent more transmissible than the current dominant strain, Alpha. Also known as B.1.1.7, Alpha is roughly 50 per cent more transmissible than the original virus.
The first mRNA vaccine you can get is the best for you," said Dr. Dominik Mertz, associate professor in the division of infectious disease at McMaster University. It is the same platform, same mechanism of action, same effectiveness to the best we know and can, as such, be used interchangeably to make sure that we get people vaccinated as quickly as possible."
The city aims to have more than 70 per cent of Hamiltonians vaccinated with two doses by the end of the summer - it was 22 per cent on Monday.
One of the key strategies to slow transmission and to keep the Delta variant under control and avoid a fourth wave is to get vaccinated as soon as possible," said Williams.
The province has instructed public health departments not to hold back any vaccine and to use their week's supply within seven days. Hamilton's medical officer of health, Dr. Elizabeth Richardson, said the city meets that target and the majority of clinics are running near full capacity.
We do make sure we have a day's vaccine on reserve to go into the next day," she said.
Vaccines are also available at pharmacies although the supply is unknown - Shoppers Drug Mart, for example, showed almost no availability in Hamilton on Monday.
In addition, primary care is giving out vaccines, particularly at David Braley Health Sciences Centre downtown and Winterberry Family Medicine in Stoney Creek, which had appointments available to book this week.
Those vaccinated with AstraZeneca can get a second dose after eight weeks instead of the optimal 12. They have the choice of getting AstraZeneca again or switching to an mRNA vaccine. Although, NACI now recommends getting Pfizer or Moderna.
If your first dose is AstraZeneca, there is evidence that you may benefit from a better immune response with the Pfizer vaccine as your second dose," said Dr. Mark Loeb, chair in infectious diseases at McMaster.
Joanna Frketich is a Hamilton-based reporter covering health for The Spectator. Reach her via email: jfrketich@thespec.com