About risks, numbers and thrombi

About risks, numbers and thrombi

We have spent a few days wondering about the risks of suffering a thrombus when receiving the AstraZeneca vaccine. However, to take this risk into account and with perspective, we must broaden the focus and remember two things: that we are numerical by nature (we are not good at calculating risks using mathematics) and that the scaremongering of the media stimulates our amygdala, which boycotts our reasoning.

Death is not the only problem

To get a general idea of ​​the risk we face, let’s use the following example. If we take a figure of 10 million imaginary people, we could expect to see 40 of these thromboses, and about 10 thromboses would have fatal consequences. Ten deaths out of 10 million vaccinated people is a one in a million chance . If we delay vaccinations for our 10 million people in a week, about 16,000 could get coronavirus, based on current levels of the virus.

If they were all older adults, say 60 years, maybe 1,000 would end up in the hospital and 300 of them would be expected to die , far more than the 10 deaths from clots after vaccination we mentioned earlier. But for the very young, the risks of hospitalization or death are considerably lower.

Given the same number of infected 40-year-olds, 16 could be expected to die, and the expected number of deaths would be even lower for people in their 20s and 30s. Therefore, for the younger age groups, the choice about whether to receive the AZ vaccine is not so clear, especially when there are so many uncertainties in all these figures.

But death is not the only problem . About a quarter of people who end up in intensive care with Covid have some type of clot resulting from the virus.

And for a long time, Covid is more likely to affect people in their 30s than those in their 70s. On average, just over 2,000 of our group would still deal with Covid symptoms three months later, and more than half of they would be limited in their daily activities by these symptoms.

And if a person is not vaccinated, what is the average risk of thrombosis? Approximately 40 men and 100 women in our imaginary group of 10 million could suffer a thrombosis, that is, approximately 12 per month.

The European medicines regulator has said that by mid-March they could have expected to see between 1 and 2 cases of thrombi in people under 50 who received the vaccine, but had seen 12, about nine times more than expected.

That said, we must take risks when we medicate . Either with a vaccine, or with heparin (which produces more thrombi): More than 300 medicines can cause thrombosis, many of them more likely than AstraZeneca.

It is the first time that we vaccinate so many millions of people (we have to expect more adverse cases) and that we follow, minute by minute, all the details through the media and social networks. Until recently, people were vaccinated for yellow fever before going on safari to Africa and did not ask about the side effects (which are also there) or the brand of the vaccine. Let’s keep that in mind the next time our amygdala tries to avoid us reasoning coldly and statistically .

Let’s use mathematics to conceptualize infrequent events as they deserve, as we must to relativize the fact that we have premonitory dreams :