Local Health Unit's Stance on COVID-19 Vaccine Mixing Backed by NACI


The National Advisory Committee on Immunization (NACI) is recommending people who received a first dose of the Oxford-AstraZeneca vaccine receive a second dose of an mRNA vaccine, such as Pfizer-BioNTech or Moderna.

Thursday's announcement reaffirms the Windsor-Essex County Health Unit's stance that mixing the vaccines is safe and effective.

Medical Officer of Health Dr. Wajid Ahmed had to address the issue publically this week after Mayor Drew Dilkens cited CDC regulations that advise against mixing the vaccines.

Ahmed says NACI's advice considers the most recent evidence on the rare instances of blood clots associated with the AstraZeneca shot and the effects of using an mRNA vaccine for a second dose.

"There's really strong data from many countries that supports the mixing of the vaccines as beneficial," he says. "It doesn't reduce the effectiveness or cause any safety concerns."

Dr. Ahmed says studies from Germany, Spain and the U.K. all support the safety of mixing the vaccines, with some data showing an increased immune response.

"There shouldn't be any concerns in anyone's mind about potential risks associated with the interchangeability of the vaccine," he added.

Using a variation of a vaccine happens all the time, as some brands aren't available year round, according to Ahmed.

"Vaccine interchangeability is not a new concept. It's been going on for some time," he says.

Ahmed says both vaccine types do the same job in training the immune system to respond to the COVID-19 virus.

He says receiving a second dose with a different vaccine type will help avoid infection or lessen the severity of symptoms for those infected.


— With files from CTV News

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