Sketchplanations

Explaining one thing a week in a sketch

Herd Immunity illustration: in a line of 10 people, we see how members of a society immunised or protected from a disease or infection (in blue) can act as a buffer between unprotected members (in red) and those vulnerable to infection (in green).

Herd immunity

When studying rates of infections, notably with measles, researchers have seen that in cases where a sufficiently large proportion of a population has been immunised or developed protection against a disease then infection rates also reduce in unprotected members of the population. In other words, the unprotected members appear to receive some indirect protection from the protected members of the population. This effect is known as herd immunity and is a tantalising goal for reducing the prevalence of epidemics.

While appealing in theory this article in Nature provides Five reasons why COVID herd immunity is probably impossible. These include:

Uncertainty around whether vaccinations prevent transmission. For example, herd immunity works when diseases can't be passed between protected members of a population to the unprotected. With COVID-19, vaccines seem to reduce symptoms but may still allow transmission.

It's also challenging to get vaccines evenly to all areas. These combined with complications brought by new variants, immunity fading before widespread vaccination is achieved, and people changing their behaviour — say, mixing more widely — once they've received some protection, means COVID-19 may be more likely to be something we live alongside rather than eradicate.

Also see: the Swiss cheese model

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Keep exploring

Don't fill the silence illustration: Someone does much better at eliciting a more in-depth response by simply waiting after asking their question rather than filling in an awkward silence
How to wash your hands illustration: the 6-step guide shows how to make sure you wash your hands thoroughly; getting right into all the nooks, crannies, creases and folds of your fingers, thumbs, palms and backs of your hands. A minimum of 20 seconds wash time is recommended.
Time Hierarchy illustration: a lush, verdant, coniferous alpine forest is depicted as a means of explaining the range of layers within any durable system that develop at different speeds. From the individual needles on the trees that develop over a year, to the surrounding biome, 10,000 years in the making.
Kitty Hawk Moment illustration: The Wright brother's first successful bi-plane, The Wright Flyer is shown taking flight; shifting the concept of human flight from the impossible to the possible.
Flatten the Curve illustration: 4 different containment strategies for a contagion outbreak and their expected effect on the number of cases detected over time are shown through a series of distribution curves.
Browse line illustration with a deer reaching up to eat the leaves off a tree and creating a tidy line at the height they can reach
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