This Twitter thread is an excellent discussion of how to understand the “do vaccines wane” discussion. Please go read it.
The US FDA today gave full approval to Pfizer, as opposed to the Emergency Use Authorization that it had given. This is important because there were entities which were not legally able to require vaccination unless the vaccine had full approval. There were a number of people in the US who were refusing the vaccine on the grounds that it was “experimental”. They don’t have that excuse any more.
This is important to Canada because spread in the US ultimately affects Canada.
Health Canada has authorized the vaccines “with restrictions”, but the restrictions are pretty low-key: they have to provide safety data on an ongoing basis. (See, for example, the Moderna authorization.)
This preprint says that if you are vaccinated, you are twice as likely to get a breakthrough case from Delta than from Alpha.
This preprint found that people were most contagious two days before and three days after symptom onset, and that people who were asymptomatic probably caught COVID-19 from someone who was asymptomatic themselves.
Really, go read this thread on vaccines waning.
OMG, if you haven’t seen the video of SARS-CoV-2 infecting bat brain cells, go watch!