A: Keep calm and remember this Nerdy Girl Mantra—“What is the BASELINE RATE?”
Humans look for patterns & meaning in everything from cloud formations, burnt toast, or the socks they are wearing when their favorite team wins.
Especially when something exceptionally good or bad happens, we’re quick to ascribe the cause to something that happened shortly before.
The tricky thing about inferring cause and effect from single events is that STUFF HAPPENS every day. In fact *lots* of things happen after we’re vaccinated. It might rain. You might buy a winning lottery ticket. Or like one participant in the Moderna Trial, you might get struck by lightning (he/she was OK as far as we know but suffered a heart arrhythmia…not due to the vaccine!).
Then how can we identify true adverse events from a vaccine? First, we look at biological plausibility- which means we can rule out that vaccines cause lightning strikes. For other health events, the detective work is more subtle. As in the trials, you need to compare the rate of adverse events to those in some comparison group that represents that “counterfactual” of what would happen without the vaccine. In the trials, this is the placebo group who does not get the vaccine but doesn’t know whether they did or not.
Similarly, out in the “real” world of vaccine deployment, we need to watch carefully for adverse events, and deaths within a short time frame after vaccination are always closely investigated.
But the key metric is comparing to that counterfactual of “what would have happened anyway?”
So, what happened in Norway? As often happens the story gained traction on social media, with 23 reported deaths among some 42,000 people given the Pfizer-BioNTech vaccine in Norway, where authorities had prioritized the immunization of nursing-home residents. Those who died were all older adults (75+) including terminally ill and very frail patients.
After a review, both the Norwegian Institute of Public Health and the WHO Global Advisory Committee on Vaccine Safety said that the fatalities “are in line with the expected, all-cause mortality rates in the sub-population of frail, elderly individuals.”
What does that mean? Sadly, those over 80, especially those already frail enough to be a nursing home, already have high BASELINE mortality. A certain number of 80+ year old’s die every day. In “normal” times Norway typically sees 45 deaths among nursing residents each week.
More generally: The chance of dying in an average week for those over 80 is about 0.2%– or 1 in 500. Thus, if you vaccinated 40,000 80+ year old’s, you would expect about 80 deaths out of that group within one week *just by coincidence*. So even though 23 people dying shortly after a vaccine sounds scary, it’s not above what is expected.
This may sound similar to another argument that many COVID-19 deaths in older adults are deaths that would have happened anyway. This is true, and EXACTLY why scientists prefer to measure “EXCESS MORTALITY” to assess the true toll of the pandemic—which counts how many deaths from any cause there have been ABOVE AND BEYOND what is expected.
Spoiler alert: Excess mortality during the pandemic has been VERY high.
The US aims to vaccinate 1 million people a day, and the UK has already approached 500K a day. In one month, that means 15-30 MILLION people will have been vaccinated, and all kinds of good and bad things will happen to some of those people shortly thereafter that have nothing to do with the vaccine.
It can be super scary to hear that someone died, or had a stroke, following vaccination. Scientists are very serious about evaluating “Adverse Events Following Immunization.” But if someone is just as likely (or more likely) to experience a health event without vaccination, the timing is almost certainly coincidence—and that’s what scientists and data nerds like us are tracking very closely. We’re watching carefully–there have already been literally tens of millions of doses given out, and things are looking extremely good for safety.
Ideally, the Nerdy Girls want to “inoculate” our readers against these types of post-vaccination scary headlines (or even worse, purposefully deceptive viral videos of strange side effects). These stories will continue to come out—stuff happens every day, some of that will happen coincidentally with vaccination.
When you see one of those headlines, take a deep breath and remember the Nerdy Girl Mantra- —“What is the BASELINE RATE?”
The Nerdy Girls are watching the data closely and have your back, no scare tactics involved.
Those Nerdy Girls
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