Several countries approve Pfizer as the second dose to AstraZeneca recipients

Monday, 14 June 2021 - 10:41

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At the start of the Covid-19 pandemic, it was unclear whether researchers would be able to create a single working vaccine, which makes it all the more surprising that the latest immunization dilemma arises from having multiple vaccine options.

With the continuing global vaccine supply shortages and an increasing variety of COVID-19 vaccines approved for emergency use, many have wondered whether combining different vaccines could be a feasible option to fast-track and simplify vaccination efforts.

The short answer from the World Health Organization, following preliminary studies in Spain, the UK and Germany and evidence coming from real-life scenarios in India, is yes.

But so far it is only with an AstraZeneca first dose followed by a Pfizer vaccine as a second dose that we know for sure that this can be done "without any problems in the sense of efficacy," said Alejandro Cravioto, WHO Chair of Strategic Management, when asked about the issue at an online question and answer session.

Recently, for example, Canada’s National Advisory Committee on Immunization updated its guidance to say that people who received the AstraZeneca vaccine as their first dose can receive that same vaccine as their second dose or get a follow-up shot of Pfizer-BioNTech or Moderna instead.

While this guidance may seem confusing, especially when the initial vaccine guidance told people to get the same shot for both doses, it does provide an opportunity to understand the safety of using mismatched vaccines, and to measure whether mismatched vaccines offer any advantage.

Meanwhile. there will be discussions today by Sri Lankan officials to obtain Pfizer vaccines from US. There are nearly 600,000 in Sri Lanka who received the first dose of the AstraZeneca vaccine and are awaiting for the second dose. 


Canada’s National Advisory Committee also said that it was possible to receive the Pfizer-BioNTech and Moderna vaccines interchangeably as first and second doses. Countries ranging from France to Finland to China to Bahrain have also outlined possible scenarios for combining different vaccines. Even the Centers for Disease Control and Prevention has interim guidance saying this is acceptable in “exceptional situations,” such as if the same vaccine is not available.

Canada's National Advisory Committee on Immunization (NACI) says people who received the Oxford-AstraZeneca vaccine for the first dose can be offered either the Pfizer or Moderna jab for the second.

The advice affects more than 2 million Canadians who received the Oxford-AstraZeneca vaccine before provinces stopped using it for first doses last month.

Several European countries are giving Pfizer or Moderna as second doses to AstraZeneca recipients, including Denmark, Finland, France, Germany, Sweden, Norway and Spain.

However, Canada's Chief Public Health Officer, Theresa Tam, cautioned that people should aim to get the same dose in a series where possible.

"NACI is not recommending [people] just use them interchangeably, but mostly try and use the same vaccine — the mRNA [type of vaccine] — for the second dose," Dr Tam told a media briefing.

"Try and find the same vaccine … but if you can't for some reason, then consider them interchangeable," she added.