Eight questions answered on the AstraZeneca vaccine controversy

The move to pause use of the UK-based manufacturer's vaccine in Canada looks more like a case of bad optics when you cut through the data


What’s really happening?

It’s a little more complicated than some of the headlines would have us believe.

On Monday, Canada’s National Advisory Committee on Immunization (NACI) recommended the use of the AstraZeneca vaccine to fight the coronavirus be “paused” in all individuals under 55. It was big news, but more a case of bad optics for AstraZeneca when you cut through the data.

Missed in the media coverage was the fact that Health Canada had already moved a week earlier, on March 24, to issue what’s called a “label change and guidance” on AstraZeneca’s COVID-19 vaccine, requesting the UK-based manufacturer “conduct a detailed assessment of the benefits and risks of the vaccine by age and gender in the Canadian context.”

The measure followed European reports pointing to more evidence of a possible “causal link” between the vaccine and “very rare” but serious cases of blood clots in some recipients. Health Canada, the United Kingdom Medicines and Healthcare Products Regulatory Agency and the European Medicines Agency all continue to recommend the use of the vaccine.

What’s the problem?

It’s called vaccine-induced prothrombotic immune thrombocytopenia, or VIPIT, a serious but treatable condition “associated with low levels of blood platelets.” Most of the cases reported in Europe have been among younger women under the age of 55. But the Public Health Agency of Canada says it’s too early to assess risk based on sex simply because it’s possible that more women have received the AstraZeneca vaccine.

How much do we know about the possible risks so far?

Research shows that serious side effects associated with the vaccine (persistent headache, shortness of breath, chest or abdominal pain or swelling and redness in the limbs) have been isolated – 1 in every 125,000 to 1 in 1 million people vaccinated so far.

Should we be worried?

The federal Conservatives described NACI’s new advice on the AstraZeneca vaccine as a “flip-flop.” That was probably predictable given the vein of science denial that runs through the party. But so far there have been no cases of VIPIT in Canada. Also, the provinces are administering the COVISHIELD version of the AstraZeneca vaccine, which is made in India. It’s the AstraZeneca brand manufactured in the UK that has produced some of the adverse side effects.

It’s easy to forget that all vaccines approved for use against COVID-19 have been granted “emergency authorization,” which means they will continue to be monitored and reviewed as they are administered to the general public.

The decision to pause the use of the AstraZeneca vaccine – a “precautionary measure,” as described by Canada’s Council of Chief Medical Officers of Health – follows a long-established regulatory protocol to review more data as it emerges.

What about those who’ve already been given the vaccine?

Health Canada says decisions on the type of the second dose that will be offered to those individuals is “an active area of study.” Those vaccinated with the AstraZeneca vaccine won’t need a second dose for 16 weeks. Advice to doctors in the meantime is that each case will require consultation with a hematologist.

How safe are the vaccines developed for COVID-19?

As of March 12, about 1 in every 9,900 doses administered in Canada have resulted in what are described as “serious” side effects (ie: allergic reaction). There have been a total of 2,209 reports of adverse side effects reported out of a total than 3.68 million doses administered as of March 19.

What does AstraZeneca say?

The results of its Phase Three trials released on March 21 in the U.S. suggest its vaccine is 76 per cent effective against symptoms of COVID-19 (85 per cent in people over 65) and 100 per cent effective against hospitalization and severe symptoms of COVID-19. 

What’s a key takeaway?

The risks associated with vaccines are lower than the risks of dying from COVID-19.

One in five Canadians already hospitalized with COVID-19 develops blood clots. COVID-19 has killed more than 15,000 Canadians so far. One in 100 Canadians who get COVID-19 end up needing intensive care.

The federal government says it has enough doses of the Pfizer and Moderna vaccines coming to vaccinate every Canadian before the fall.

But pausing the use of the AstraZeneca vaccine by several countries in Europe has also led to the stopping of the cross-border flow of the vaccine, slowing the fight against the pandemic as more deadly strains of the virus contribute to a third wave globally.  

@enzodimatteo

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