The effectiveness of vaccination

I look forward to being vaccinated for COVID-19. However, being vaccinated does not mean that I can ignore the risk of contracting COVID-19 from then on. Vaccination simply makes the risk much smaller.

Refer to this graph:

You and I are currently in the blue sector. The probability of contracting the disease is relatively high. By "relatively" I mean relative to the purple, orange, and yellow sectors. As long as we remain in the blue sector, each of us can minimize the risk by observing social distancing, practicing good personal hygiene such as hand-washing, and (most importantly) staying away from confined spaces where people who don't wear masks are or have recently been. We know about life in the blue sector already so there's no point in my writing about it.

Time A is when I get the first vaccination. I enter the purple sector. Note that the risk of contracting COVID-19 does not decrease immediately; there is no indication that being vaccinated only once confers any immunity. But after the second vaccination, the risk begins to fall rapidly. Even so, it takes a little while after the second injection for immunity to be maximized. The purple sector represents this delay.

At time B, the vaccine has conferred on me as much immunity as it will. I enter the orange sector. Note that the risk of contracting COVID-19 during the orange sector is not zero. The vaccine is only 95% effective, so the risk of contracting COVID-19 never falls to zero. Therefore I will still have to make decisions about, for example, going to an indoor hockey game. Over time, the risk in the orange sector falls slowly as more and more people become immune.

Of course, even though the risk in the orange sector never goes to zero, the risk is much lower than in the blue sector before I was vaccinated. Vaccination is still the right thing to do even if the vaccine is not perfect. Every person who gets vaccinated pushes us farther to the right in the orange sector.

So what's time C? The yellow region represents the indefinite period of time when the risk of contracting COVID-19 reaches a baseline. The virus will still be out there, and not everyone will be immune, and I won't be completely immune either. This yellow sector could extend for decades — or at least until someone develops a vaccine that is 100% effective. In the absence of a perfect vaccine, COVID-19 will remain a threat to health in the sense that heart trouble, cancer, stroke, automobile accident, etc are threats to health. We will simply have to accept this threat like we accept the others.

It's too soon to say what life in the yellow sector will be like. Travel in third world countries, for example, may still be somewhat risky compared to travel in first world countries. But that's always always been true. What level of caution will I exercise? Will I expect people around me to wear masks if I'm uncertain of their vaccination status? The more antivaxxers there are, the more I will have to think about that. Will hand sanitizer and household bleach still be difficult to find at the grocery store? I don't know.

The combination of medical science to produce a highly effective vaccine and the political and social determination to ensure near-universal vaccination eventually eradicated smallpox. I'd like to believe that in 25-50 years, the SARS-CoV-2 virus will be eradicated completely. But because the SARS family of coronaviruses appears to mutate, don't count on complete eradication. Ever. Like the risk of nuclear war, we will have to accept the risk of some kind of SARS as a fact of life.