If more than one vaccine becomes available, could taking two different vaccines boost the effectiveness?

We do not know the answer to this yet as it is still being investigated in clinical trials. Currently, the COVID-19 vaccines are not considered interchangeable.

There is limited data available on the interchangeability between COVID‑19 vaccines, such that, where possible other vaccines should not be substituted to complete the course. So far, the only COVID-19 vaccine available for use in New Zealand is Comirnaty (Pfizer/BioNTech). Other vaccines, including the COVID-19 vaccine AstraZeneca and COVID-19 Vaccine Janssen have been approved by Medsafe but their role in the vaccination programmes is under discussion.

To be fully immunised with Comirnaty, two doses are required, to be given at least 21 days apart (ideally, six weeks apart). There is no maximum duration between doses, so it is not necessary to restart the course or give a third dose if it has been longer than 6 weeks since dose one.

For the WHO position on mixing COVID-19 vaccines, please click here.

Last updated: 06 September 2021