Saturday, January 30, 2021

Life After a 95% Effective Vaccine

Congratulations, you scored your double dose of the Pfizer or Moderna COVID-19 vaccines and you are ready to rock and roll, Baby.

Does it matter that the pandemic is still raging outside your door? For those of us old enough to remember Rowan & Martin’s “Laugh-In” the answer is clear: You bet your sweet bippy it matters.

Ninety-five percent is not 100%. You still have a 1/20 chance of getting the disease given a significant exposure to the virus. Your case may not be as virulent as without the vaccine, but the scientific jury is still out—especially regarding the long-term effects of the disease.

Here’s how to think of your risk. You decide to go to in-person church (or some other super-spreader event). Let’s say for discussion that before your vaccine you had a 50/50 chance of catching the disease. (Even in super-spreader events, not everyone was infected.) With the vaccine, your chances fall to 2.5% for that one event. Life’s for living, right? No more sheltering in place because that doesn’t sound too risky.

Although, on average, if forty of you made that same decision, one of you will come down with the disease.

But okay, you take that chance. Of course, if you are going to chance it once, you’ll chance it twice, three times, ’cause heck, the odds are 39-1 against anything bad happening.

Except that’s not the way probabilities work. To stay healthy, you must win against every encounter with the disease. Your chance of winning each one (based on the assumptions above) is 97.5%. To determine the chances of staying healthy after two events, you multiply the chance of staying healthy for each of those events. 97.5% x 97.5% = about 95%.

After 10 events, your chances of not catching the disease are down to 78%. They become less than 50% after 28 such events. If you are part of a couple who attend the events together, the chances of both of you staying healthy drop to below 50% after only 14 events.

To allow us to get back to normal, we must significantly decrease our chances of being exposed to the disease in gatherings. There are only two ways to do this: Increase effectiveness of the vaccine (nope – it doesn’t work that way) or decrease the chances of being exposed during an outing. That means continuing to make safe decisions until enough people are vaccinated (or have caught the disease and are no longer contagious) so the chances of being exposed in what had been a super-spreader event decline significantly.

The math is powerful. If we can drop the original assumption of 50% to 10%, our chances of staying healthy after 28 events increases from 49% to 87%. If we can reduce the chance of exposure to 5%, the 87% after 28 events increases to 93%. This is the power of herd immunity, but we are a long way from reaching those levels of protection.

Even if you don’t quite understand the math, believe its message: your vaccination improves your odds of staying COVID-19 free, but only if you don’t take unnecessary risks.

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James M. Jackson authors the Seamus McCree series. Full of mystery and suspense, these thrillers explore financial crimes, family relationships, and what happens when they mix. Furthermore, a novella is the most recent addition to the series. You can sign up for his newsletter and find more information about Jim and his books at

1 comment:

  1. Depressing to think our lives will be like this for the foreseeable future.