Covid-19, we better understand the risk of an adverse event after the vaccine

Covid-19, we better understand the risk of an adverse event after the vaccine
Covid-19, we better understand the risk of an adverse event after the vaccine

The perception of risk is often subjective and instinctive, but the numbers tell us that every day we expose ourselves to much higher risks than those of the rare adverse effects of vaccines against Covid-19. Here are some comparisons

(foto: Mohammad Shahhosseini/Unsplash)

One of the most difficult issues to communicate, long before the start of the Covid-19 pandemic, is theexposure to risk and membership danger to which we are exposed in an emergency situation. It could be said that the reason and the science require us to make it primarily a numerical issue, of quantitative analysis and statistics, but it has been known for some time how much the issue actually is – especially when we move from evaluations between professionals to great audience – is also permeated by aspects related to subjective perception, all’emotionality and to our innate instinctive reaction facing a potential danger, which sometimes translates into apparently irrational actions dictated by cognitive distortions of various kinds.

A trait common to many evaluations that are read online and in newspapers about the vaccination risk (and which are also heard in the collective chatter) is the attempt to put a comparison the various vaccines. Not only in terms of overall effectiveness and against specific variants, but also in terms of the incidence of adverse effects more or less relevant that may follow vaccination. So, for example, we focus on whether one or the other formulation has a slightly higher or a little lower frequency in the rare side symptoms which can determine: an undoubtedly important issue to monitor at the level of pharmacovigilance, and returned to the fore in the last few days after the umpteenth changes to the indications for use for the vaccine Vaxzevria by Oxford-AstraZeneca. But which could lead us to think that comparisons between vaccines are crucial, when instead, even in the worst case scenario, the risk in question is extremely low.

An undoubtedly remarkable example of the comparison work is that offered by Reuters, while in other cases it was preferred to focus on the general comparison between Covid-19 risk vs vaccination risk (here the University of Cambridge, to give an idea) or on a comparison between the risk of thrombosis with and without vaccination. In absolute terms, however, to date both for the Anglo-Swedish vaccine and for the branded one Johnson & Johnson (which currently has different indications for use, although it is not clear why), estimates of the incidence of rare thrombotic side effects are one for every 100 thousand vaccinated, if not even less.

Does it make sense to compare with other drugs?

A further possibility of comparison, again with regard to the risk of adverse effects, is to compare the anti Covid-19 vaccines with others commonly used drugs. The result is obvious, even without going into the details of the numbers: vaccines are by far among the safest drugs, both in general and in the specific case of those against Covid-19. And several of the most common painkillers, antipyretics and anti-inflammatories have a much higher incidence of side effects – even serious ones – than those of a vaccination.

On a communicative level, however, this argument often struggles to hold up, because the typical objection of those who are hesitating to get vaccinated is that one thing is the drugs we take. when we are sick (accepting more willingly to take a risk, but in exchange for a perceptible benefit) and another are those who have a preventive purpose, which we assume when the problem has not yet manifested itself. Not that the objection itself is conclusive – the vaccine reduces the risk of complications in those who become infected with the virus, and the risk of contagion is certainly not negligible, indeed unfortunately quite high, in the long term – but we pretend to welcome it.

One of the exceptions to this impasse communicative are the contraceptives for female use, which certainly are not normally medications from sick people yet they have already shown to have a certain correlation with the thromboembolic events themselves: not one in 100 thousand like the anti Covid-19 vaccines, but between 3 and 9 every 10 thousand, or at least higher than 2 every 10 thousand according to a mammoth study by British Medical Journal of the last decade. This obviously does not mean that it is a bad idea to take a contraceptive (and God forbid), but that from the point of view of the most serious adverse effects the risk you run is at least ten times higher compared to that of vaccination.

More than the vaccine, the light bulb and the bath in the sea

In summary: it may not be enough to argue that the risk of getting vaccinated is much lower than that of the disease from which it protects; it may not be enough to show that the vaccine has a much lower level of risk than commonly used drugs; it may not be enough to compare the incidence of certain adverse effects with those that occur in any case in the general population; and it may not be enough to give the absolute numbers of these risks (specifying, for example, that only in one case out of three the thrombosis caused by the vaccine translates into a fatal clinical outcome, and that if instead of thinking about the twenties we pass to the fifties the risk of thrombosis is further reduced to a third). But what about the risks that, by healthy people, we run daily in making ours routine activities, and what numbers in hand are much more problematic than being vaccinated?

Let’s take some examples. Also referred to 100,000 people, according to the Winton Center for Risk and Evidence Communication and an analysis of the Bbc, the annual risk of dying fromcar crash it is estimated at 38 for young people and 23 for middle-aged people (compared to 11 and 4 in the case of the AstraZeneca vaccine). To die for any kind of accident fluctuates between 110 and 180 each year, and only in the case of deaths due to a lighting bolt we have another 1 to add every year. The risk of not surviving vaccination, in other words, is comparable to that of being victim of a murder in the next 30 days, or what you run into doing a drive of 400 kilometers.

Indeed, in many cases, even when you are at the vaccination center for the injection you are safer than anywhere else, including the walls of your home. For example, statistics in hand, the risk of dying climbing a domestic ladder steps for ordinary maintenance operations (such as changing a light bulb) is 9 times higher than vaccination if you are a woman, and 37 times if you are a man, taking into account the probability of accidental falls and the risk of being electrocuted with the electric socket. The probability of dying from the Covid vaccine is roughly half that of being killed by your partner in a western country, and roughly half as well as that of to die by drowning (due to illness or other) during every single swim in the sea.

Every bike ride has a risk of fatal death compared to a dose of Covid viral vector vaccine that is 2.5 times higher, and the same is true on average for each day spent in the workplace. Comparing with other long-standing statistics, the risk of getting vaccinated corresponds to that of traveling 16,000 kilometers in plane, o 100mila in train, a couple of hang-gliding trips, a to stroll for a total of 270 kilometers (not all at once) or to travel 95 kilometers on a motorcycle. Again, in indirect terms and for example through the diseases it can cause, a vaccine corresponds to the risk of smoking 14 cigarettes or drink 5 liters of wine.

On balance, a person who leads a full-fledged life media (no extreme sports, no excesses of alcohol, smoking, drugs or junk foods, no special work activities, extravagance or useless gambling) has a risk of dying for every week where he simply lives – that is, he gets out of bed and goes about his day – equal to double of what you run by getting vaccinated. The perception of risk will in any case remain subjective, but not getting vaccinated for fear of adverse effects rationally makes little sense if you intend to continue to lead a life that is not just lying on the mattress, and that includes, for example, moving, working, take some medication as needed, live with your partner or go on vacation.

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