You might not take kindly to being lumped together with the rest of humankind into a ‘herd’, but when it comes to your health you should be thankful to be part of a grand collective.

This is because of an effect known as ‘herd immunity’. It means that when enough of us are vaccinated against a contagious disease, most people who aren’t immunized are also protected.

It’s a phenomenon that helps people who can’t be immunized, including newborn babies, pregnant women, patients undergoing chemotherapy and those with compromised immune systems.

6 seconds that explain how and why

Drawing on data published in Epidemiologic Reviews, Reddit User theotheredmund created a GIF that neatly summarises the impact of herd immunity.

Image: Reddit

Areas with high levels of immunization are able to largely contain infections. From 90% vaccination levels and up, the number of infected people is kept low, protecting even individuals who have not been vaccinated.

As the US Department of Health and Human Services explains, herd immunity relies on a “critical portion of a community” being immunized.

Doubts about vaccination

In recent years, an anti-vaccine movement has emerged around the world. Concerns over safety, effectiveness and religious objections have all been raised. Research last year showed the scale of the problem.

As this map - created by Scientific American using data from the study - shows, concerns about safety are highest in France, where 41% said they don’t think vaccines are safe. Although only 67 countries were included in the survey, the map emphasises that this is a global issue.

Image: Scientific American

The value of vaccines

Organizations such as the WHO, UNICEF and Gavi have partnered to highlight the value of vaccines and combat negative attitudes.

According to Gavi, vaccines currently save between 2 and 3 million lives a year.

There are broader benefits as well. Preventing illness can improve cognitive skills, physical strength and ensure an uninterrupted education. That’s good for individuals, but also for society generally. As this animation shows, it’s well worth the cost:

There’s still significant work to be done though. The WHO reports that “an estimated 19.4 million infants worldwide are still missing out on basic vaccines.”

Vaccination against haemophilus influenzae is a case in point. The most common strain - type b - causes meningitis and pneumonia but immunization levels vary significantly across the world.

Coverage is estimated at 90% in the Americas, but in the Western Pacific and South-East Asia this plummets to 25% and 56% respectively.