Mitigation Measures
This article reports that the land borders to the US will stay closed to non-essential travel until at least 21 August. American tourists will be able to come here, but Canadian tourists won’t be able to go there by land. (Canadians can still fly to the US with a negative test. The US has never stopped Canadians from flying in.) Essential travellers to the US can still cross, without proof of vax or a negative test.
Vaccines
This thread reports on data from the Israeli Ministry of Health which shows waning immunity of the Pfizer vaccine: people who had gotten the vax 12 weeks ago were more likely to catch COVID-19 than people who got vaxxed three weeks ago. The comments, however, are complaining that they did not adjust for age, and older people got vaccinated first.
Note for Canada: Israel had a short interval between doses, and there is some data which says that a longer dose interval (like what Canada has mostly used) is better.
Recommended Reading
This article discusses “correlates of immunity”, i.e. things scientists can measure easily in a test tube which correlate with a vaccines effectiveness.