The concept of herd immunity – the principle by which a high percentage of vaccinates prevents infectious agents from circulating and triggering epidemics – we have written several times. But as often happens, the images are more effective than words: in this animation, the user of Reddit theotheredmund shows, in a matter of seconds, because the only way to stem the path of pathogens is to vaccinate the highest percentage of people possible.
AT RISK. The answer to the question: why should I vaccinate (or vaccinate my children) ?, is in the blue dots of these images, representing who is unable to be vaccinated: for example, newborns or immunosuppressed patients, because under chemo, or seropositive.
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RACE AT OBSTACLES. As seen in the GIF, low levels of vaccinated allow viruses and bacteria to spread very quickly (their advance is indicated in red). Mean levels of vaccinations slow down the progression of epidemics, but do not adequately protect the most vulnerable.
On the other hand, when a high percentage of coverage is reached (from 90% upwards), the pathogens wishing to spread find, before them, a blocked road, made of protected individuals (in yellow in the image): in this case, the majority of the population, including non-vaccinated, is protected.
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HOW IT HAS BEEN CREATED. The animation was obtained through a simulation in R, an open source programming language created to elaborate statistical models. It is not based on real data related to one or the other disease, but on projections based on the percentages of effectiveness of the flock immunity in preventing the diseases reported in a 1993 article, published on Epidemiologic Reviews.
As you can see, the only way to forget about some epidemics is to focus on the large numbers of the vaccinated: after all it is only thanks to the immunity of flocks, that today we can not worry about diseases such as polio and smallpox.