Herd Immunity – and how every Kiwi can be a hero

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‘Herd immunity’ is a term that’s cropping up a lot these days – and although it has nothing to do with the dairy industry, and everything to do with keeping humans as healthy as possible, the concept actually has its basis in laboratory rats! But first things first, what does ‘herd immunity’ actually mean?

Bacteria and viruses (for the sake of simplicity, we’ll call them both ‘germs’) spread through communities by transferring themselves from one person to another. This can happen, for example, when germs escape from an infected person as they cough or sneeze. In some cases, it can happen when germs are passed on from one person to another via a surface which a ‘sick’ person has touched.

Once a person is vaccinated, it’s generally assumed that the germ they’re vaccinated against can no longer be passed from one person to another – or, at the very least, that this is most unlikely to happen. It’s this that helps stop the spread of the disease.

For those of you who think visually, imagine a whole bunch of people (we’ll call them a ‘herd’) in a room. A large percentage of the herd are wearing yellow t-shirts to show they’re vaccinated against a germ. The non-vaccinated members of the herd, who are randomly scattered among the vaccinated members, are wearing blue t-shirts. If the germ gets into the room, it’s very unlikely that it will harm anyone. That’s because, to do so, it will almost always have to get past the buffer of yellow t-shirters in order to reach the non-vaccinated blue t-shirters. Even if the germ happens to strike it lucky, and encounters a blue t-shirter first, it is extremely unlikely to get any further because the yellow t-shirters all around the blue t-shirter it have been vaccinated.

But, you know what? Herd immunity can happen without anyone being vaccinated. That’s because, when someone catches a germ, their immune system produces special proteins called anti-bodies. These antibodies behave like a vaccination, protecting the sick person so they (hopefully) won’t get sick with the disease next time it shows up. Sounds nice and natural, doesn’t it? But there’s just one catch – and it’s a biggie.

If you catch a disease, your antibodies might not kick in fast enough to save you – in fact, with many diseases, you stand a good chance of dying before you recover. If you’re pregnant, you might even pass the disease onto your unborn baby, with catastrophic results (in the case of rubella – also called German measles – an unborn baby can be left with hearing loss).

When it comes to Covid 19, if we wait around for herd immunity to develop naturally, our hospitals will be overrun with sick people, and many frail members of our community will die from the disease. Many others will be seriously affected by other medical problems, because there will be little hospital space left to treat them.

Just as we’re hearing a lot about ‘herd immunity’ these days, we’re also hearing about ‘Vaccination Heroes’. That’s because people who say ‘yes’ to vaccines – against any disease – are not only protecting themselves, they’re also helping to protect everyone else. This is especially important for people in our communities are simply not able to receive a vaccine. Their immune systems may be too frail, or they may be too young. Taking vaccine jabs helps protect them from diseases, too.

Now, about those rats we mentioned at the start of this article, and how they brought about the term ‘herd immunity’: A group of rats was used in an experiment in the early 1920s to see if vaccinating enough of a them would help stop a germ spreading to others in their group. The scientists referred to the group of rats as a ‘herd’, and so the term ‘herd immunity’ was born.