You may read this post as the continuation of the one I made last year. Evaluate the risk caused by an action by comparing it with situations without that action. That is the core of the risk-benefit trade-off in decision-making. A third factor is missing in the equation, namely, the cost.
A new study published in The Lancet is the basis for this post. The report compiles the incidents of myocarditis and pericarditis, two well-known side effects linked to the mRNA vaccines against COVID-19. The data covered four health claim databases in the US and more than 15 million individuals.
The results
First, the overall summary: the data from four Data Partners (DP) indicate 411 events out of the 15 million studied who received the vaccine. Details of what is provided by each of the DPs are,
| Data Partner (DP) | Total vaccinated | Total Observed myocarditis or pericarditis events (O) | Expected events (E) (based on 2019) | O/E |
| DP1 | 6,245,406 | 154 | N/A | – |
| DP2 | 2,169,398 | 64 | 24.96 | 2.56 |
| DP3 | 3,573,097 | 94 | 40.08 | 2.35 |
| DP4 | 3,160,468 | 99 | 44.61 | 2.22 |
I don’t think you will demand a chi-squared test to get convinced that the two mRNA vaccines have an adverse effect on heart health. Age-wise split of the data gives further insights into the story.
| Age-group | Observed Events | Total vaccinated | Incident Rate (per 100,000) | Expected Rate (per 100,000) |
| 18-25 | 153 | 1,972,410 | 7.76 | 0.99 |
| 26-35 | 62 | 2,587,814 | 2.40 | 0.95 |
| 36-45 | 63 | 3,226,022 | 1.95 | 1.11 |
| 46-55 | 62 | 3,597,292 | 1.72 | 1.3 |
| 56-64 | 71 | 3,764,831 | 1.89 | 1.63 |
The relative risk is much higher for younger – 18 to 35 – age groups. But the absolute risk of the event is still in the single digits per hundred thousand. And this is where we should look at the risk-benefit-cost trade-off of decision-making.
The risk
First and foremost, don’t assume all those 411 individuals died from myocarditis or pericarditis; > 99% recover. To know that, you need to read another study published in December 2021 that reported the total number of deaths to just 8! So, there is a risk, but the absolute value is low. The awareness of the risk should alert the recipients that any discomfort after the vaccination warrants a medical checkup.
The benefit
It would be a crime to forget the unimaginable calamity that disease has brought to the US, with more than a million people dying from it. A significant portion of those deaths happened prior to the introduction of the vaccines, and even after, the casualties were disproportionately harder on the unvaccinated vs the vaccinated.
The cost
At least, in this case, the cost is a non-factor. Vaccine price, be it one dollar or 10 dollars, is way lower than the cost of the alternate choices, buying medicines, hospitalisation or death.
Managing trade-off
Different countries manage this trade-off differently. Since the risk of complications due to COVID-19 is much lower for children and the youth, some allocate a lower priority to the younger age groups or assign a different vaccine. However, it is recognised that avoiding their vaccination altogether, due to their low-risk status, is also not an answer to the problem. It can elevate the prevalence of illness in the system and jeopardise the elders with extra exposure to the virus.
References
Risk of myocarditis and pericarditis after the COVID-19 mRNA vaccination in the USA: The Lancet
Myocarditis after COVID-19 mRNA vaccination: Nature Reviews Cardiology
How to Compare COVID Deaths for Vaccinated and Unvaccinated People: Scientific American
