My doctor, Alex Lickerman, has put up post #13 in his continuing series on the medical science of coronavirus and the pandemic. This short but informative post (click on screenshot below) deals with a question we all have:
First, the effectiveness. Alex summarizes numerous studies showing how effective a vaccine is. Remember, though, what that number, expressed as a percentage, means. If a vaccine is 95% effective, it means that in a situation in which a certain percentage of people get infected, say 30%, then the chance you will get in infected is (100% – 95%) X 30%, or 1.7%. Note that this does not mean that your chance of getting infected is 5%: it’s lower than that because not everybody gets infected when they’re not vaccinated.
Here are some effectiveness estimates taken by Alex from the literature:
Single dose Pfizer: 70%
Double dose Pfizer: 85%
Single dose Pfizer and Modern considered together, single dose: 80%
Double dose ” ” ” ” double dose: 90%
The two above figures are also the same in another study not specifying vaccination
The 80%-90% holds for both symptomatic and asymptomatic infections; this means that yes, you can be an asymptomatic carrier if you have been fully vaccinated, but the chances are very small.
Pfizer and Moderna combined (both mRNA vaccines): effectiveness: over 96%
Now remember again what these figures mean, because people get that meaning wrong all the time. Here’s one example I quote from the article:
A CNN article was skeptical of this data, arguing that “real-world studies of the Pfizer-BioNTech and Moderna vaccines show they are only 90% protective against the coronavirus, not 95% as reported in clinical trials. Translated into reality, that means for every million fully vaccinated people who fly, some 100,000 could still become infected.” Importantly, this is not what 90 percent effectiveness means! Ninety percent effectiveness means the vaccines reduce the rate of infection by 90%. To calculate a person’s absolute risk of getting infected after having been vaccinated, you have to start with the base rate of infection, which is different in different contexts. It would be true that “for every million fully vaccinated people who fly, some 100,000 could still become infected” if the base rate of infection for those million people was 100 percent. Yet the highest rate of infection we’ve seen in published contact tracing studies was around 30 percent (for spouses of infected people). This means that post-vaccination rates of COVID-19 infection in the vaccinated population are at most 90 percent less than 30 percent, or 3 percent. And that only if everyone who’s been vaccinated has an infected spouse.
In fact, the CDC reported that, as of April 20, 2021, out of 87 million fully vaccinated people there were only 7,157 breakthrough infections (0.008 percent), only 498 hospitalizations (0.0006 percent) related to COVID-19, and only 88 deaths (0.0001 percent) related to COVID-19.
Alex’s bottom line:
The mRNA vaccines are extraordinarily effective at preventing both symptomatic and asymptomatic infection and therefore at preventing transmission of SARS-CoV-2. Most importantly, if you’re fully vaccinated, your risk of dying from COVID-19 is 0.0001 percent.
What about the variants?. In answer to the question of whether the vaccines work against the variants, Alex says “yes”, at least for variants currently circulating. He adds that more data are to come.
Here’s Alex’s conclusion, which happens to echo the same conclusions reached by Bari Weiss in a piece published on her site this morning:
CONCLUSION: Given the incredible effectiveness of the vaccines at preventing both symptomatic and asymptomatic disease, and therefore disease transmission, and given that the rates of death from COVID-19 in vaccinated people is 0.0001 percent among all vaccinated people in the U.S. (an analysis that also included the J&J vaccine), if you’ve been vaccinated, we consider it reasonably safe to dine indoors, travel, and gather with even unvaccinated people. Living in the world has, of course, never been risk-free. Yet we can now say that with the advent of effective vaccines against SARS-CoV-2, the risk of living as you did before the pandemic has returned to what it was before the pandemic.
Here’s Weiss’s piece, which I think is free, though I’ve now subscribed. Click on the screenshot: