VANCOUVER -- People who received an mRNA vaccine for their first dose are being advised to stick with that type for their second dose.

While health officials have said it's fine to mix and match between mRNA vaccines such as Pfizer-BioNTech and Moderna, or to follow up an AstraZeneca vaccine with ad mRNA shot, provincial health officer Dr. Bonnie Henry said Tuesday that people shouldn't seek a dose of AstraZeneca if their first dose was an mRNA vaccine.

Although Henry did not explain her reasoning behind the one-directional approach with the AstraZeneca vaccine, the shot is associated with a very rare risk of blood clotting.

“I don't see a scenario where we would give AstraZeneca as a second dose (to people who received mRNA first), with the one exception of people who had an allergic reaction to an mRNA vaccine,” she said.

However, for those who received AstraZeneca as their first dose, B.C. continues to recommend that people choose whether they want to follow up with that type for their second dose, or whether to mix it up and get an mRNA vaccine.

Last week the National Advisory Committee on Immunization (NACI) updated its recommendations around the AstraZeneca vaccine. It’s now recommending that people who received a first dose of the AstraZeneca vaccine receive a second dose of an mRNA vaccine, such as Pfizer or Moderna. The advice is based on emerging evidence that suggests a better immune response when a person gets AstraZeneca as their first dose, and then follows it up with an mRNA vaccine for their second dose.

Although B.C. hasn’t changed its policy, and is continuing to offer the AstraZeneca vaccine, there’s been a decline in the number of people seeking the AstraZeneca vaccine.

It’s leaving some to wonder whether there will be a surplus of AstraZeneca, and whether an enhanced immune response is also seen when you get mRNA first and follow it up with AstraZeneca. Neither Henry nor Health Minister Adrian Dix seemed concerned that there would be a glut of AstraZeneca, and Henry recommended against AstraZeneca as a second dose after an mRNA vaccine.

They both emphasized that many more mRNA vaccine shipments are arriving this month.

“Overall we know that we are getting a net increase of vaccines in June,” Dix said