The Elusion of Herd Immunity 

Despite a vaccination rate that should be the envy of anywhere in the world, our efforts to reach some version of herd immunity appear to be stalling - just as the continuing emergence of variants makes that goal more elusive.


As of now, 78% of Toronto residents have received one dose; about 56% are fully vaccinated. At this time last year, numbers that good this soon seemed unimaginable. But the coronavirus has brought many surprises, both good and bad.


If we were still dealing with the original version of the virus, we would be weeks away from herd immunity, the point at which such a high proportion of the population is resistant to the virus that it has few avenues to spread and may begin to subside.


But the worldwide spread of the virus led to constant mutations, some them labelled "variants of concern". These spread more rapidly, made people sicker faster, and showed an ability to partially evade antibodies from infection or vaccination.


The 50% more transmissible Alpha variant was partially responsible for our Second Wave last fall and early winter. That has now been pushed aside by the Delta variant, at least 50% more contagious again, and primarily responsible for the Third Wave.


Other dangerous variants, such as Lambda, which has swept through Peru and other parts of South America, are already here. We'll know whether any of these are a severe threat when, in Darwinian fashion, they demonstrate their fitness by pushing the others aside. But, with many parts of the globe hardly vaccinated and the virus able to spread and mutate rapidly, it's just a matter of time until that happens.


But vaccines work. In recent months, there have been a flurry of studies measuring vaccine effectiveness against the most dangerous variants. Percentages for protection against infection have varied from low 60s to the 90s, depending on such variables as whether the studies were conducted in the lab or in real world conditions and who was in the sample group.


But there are several consistent findings:

  • All vaccines approved in Canada are extremely effective at protecting against severe illness and death – even against Alpha, Delta and other variants of concern

  • All vaccines are far more effective after two doses

All of which is very good news to those of us who are fully vaccinated and others who will get there soon, two weeks after their second dose. If you know someone who has not yet been vaccinated, please encourage them to research the facts and/or speak with someone whose medical advice they trust, such as a family doctor.


It's for their own sake but also for ours.


To reach herd immunity now, we need the vaccination rate to be well above 80% and more likely closer to 90. There is no longer any shortage of vaccine supply, so there are now more appointments than people to fill them. This presents an opportunity for anyone who wants a first dose or wishes to move their second dose earlier than originally scheduled, provided the first dose was at least eight weeks ago.


To book your first or second appointment, visit the COVID-19 vaccination booking portal here.


Several city clinics are now accepting walk-ins, and outreach is improving among those who need translated information (see below for more information on both of these). If your first dose was AstraZeneca and you haven't yet received a second dose, a recent study from Germany provides additional evidence that a second dose of an mRNA vaccine, on top of a first dose of AstraZeneca, provides extremely good protection.


For anyone whose second dose is Moderna when they were expecting Pfizer, these are both mRNA vaccines, considered equally safe, effective, and completely interchangeable.


The cautious approach to re-opening, combined with vaccinations, is paying off. As the summer progresses, we can gradually resume much of our regular lives.


This week's song is (sort of) about being open to better things. The lyrics are a tad trite, but the tune is awfully catchy and the vocals are great. The singer, by the way, is Mickey Thomas; Elvin Bishop is the guitar player.


-John