We all want to have one consistent recommendation on what to do in the face of COVID-19.  Unfortunately we have seen advice change, at times a complete 180!  At the start of the pandemic we were told not to wear masks as that could increase transmission, then we were told we have to wear masks.  With the Astra Zeneca vaccine we have been told that it needs to be used for those less than 65, now we are told it needs to be used for those over 55.  And now we are told we are going to stop using it.  Why dose this happen?

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This is certainly unprecedented times, and we are all drinking from a firehose of information.  Experts are receiving new information and reviewing old information furiously, and updating their recommendations as a consequence. 

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Certainly with the masking issue we can see how the decisions flowed: initially there was concern about masks causing people to touch there face more and therefore bring virus to the nose and eyes were it could enter the body and cause infection.  This was based on opinion as there actually was little data on masking and its benefits.  It was never discouraged for health care workers who are trained in the proper application of masks.  Then there was a practical concern - if masking was encouraged, it could precipitate a lack of availability of masks for those who actually have to take care of people who are sick with disease - and this was indeed seen - hence the recommendation not to use medical grade masks.  Then epidemiologists went over actual real world experiences in other countries and could see the real benefit that masking gives if applied universally - so the recommendation for everyone to wear cloth masks.

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Similarly with the Astra-Zeneca vaccine.  In Europe, a cluster of cases of people having blood clots after being immunized was noted through the vaccine adverse reaction surveillance, and as a precaution vaccination with that vaccine was stopped.  It is important to understand that things like death, blood clots, and myriads of other problems occur all the time whether people get vaccinated or not.  When the vaccine was approved as being safe, it had been checked in over 30,000 people - but could a an adverse effect occur for 1/100,000 people - of course - and that is why our European colleagues paused vaccination.  The data was reviewed and the European Medicines Agency (EMA) did recommend resuming the use of this vaccine.  In Canada, our regulators reviewing the data came to a different conclusion, as the number of cases seen in the millions of doses given around the world did not seem to reach a significant value and so never recommended pausing the vaccination.  Some decisions are clear cut and easy to make, and some decisions are not so clear and then we can get different recommendations.  Similarly the EMA initially approved the Astra-Zeneca for all ages whereas Health Canada approved it for those less than 65 initially.  This is because the majority of people in the Astra-Zeneca trials used for their submission to Health Canada were less than 65 and relatively few over.  The EMA made a perfectly sensible decision, that if it is safe and works for younger people, it will be safe for older too.  Health Canada and the National Advisory Council on Immunization (NACI) also made a perfectly sensible decision that they wanted to see more data for those over 65 - which they were then able to do with the millions of doses administered in other countries to people of this age group.  Now NACI is suggesting we take a pause from administering the Astra-Zeneca vaccine to those younger than 55 - and this is because when looking at subgroups - they found that maybe the risk of blood clots is higher amongst younger people (in combination with younger people being a lower priority due to lower risk of adverse outcomes), especially younger women.  This is a reasonable decision, although it would be entirely reasonable to go with the EMAs advice to continue to offer it, as this problem is rare - much less than 1/100,000.  The risks of blood clots if you get COVID-19 are much higher.  Since I originally wrote this, it looks like it is less rare, perhaps even at the level of 1/60,000 - and doesn't seem to depend on age (This is still quite rare, and every 10 days 1/60,000 people in Ontario are currently dying from COVID-19).  Ontario has decided to stop offering the shot, especially as we are reaching younger age groups that have lower risks of dying from contracting COVID.  There is also the additional problem that supply of this vaccine is now being redirected to India's outbreak and so future doses may not be available for 2nd shots.  Note that the risk of the severe blood clotting is much less with the 2nd shot compared to the first - estimates I have heard of are around 1/1,000,000.  A study has been performed in England looking at using a different vaccine for the 2nd shot - and I've heard the data looks promising and hopefully we will know soon if that will be a good option for those who have received their first AZ dose and will not be able to get a 2nd.

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Although it is frustrating, the fact that pauses in vaccination occur should not increase anxiety about immunization, but rather reassure us that our health experts are vigorously looking out for our safety, and that even rare risks are being closely looked into, despite the political and social pressure to just get people immunized and hopefully stop this pandemic.  That experts change advice is reassuring to know that they will not stick with a course of action just based on pride, or trying to keep a consistent message, but that advice will change depending on evidence that accumulates.

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Certainly, immunization is our only hope to get out of the mess that we are in.  People just getting sick and becoming immune is not an option - somewhat initially tried in England and Sweden with bad results.  Pretending the virus does not exist has not been helpful in the United States or in Brazil.  Certainly, in North America we do not have the public health culture of China, so we are not going to be able to stop the virus by public health measures - (for good or for bad it has been demonstrated that with enforced quarantine, enforced mask wearing, enforced contact tracing apps, with use of cellphone tower data and CCTV cameras to chase down reticent contacts, and travel restrictions even within jurisdictions, it has been demonstrated that this disease could be controlled - though with Omicron that has really been tested - as can be seen with the disastrous results in Hong Kong - likely driven by low vaccination rates in seniors there).

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