Herd immunity and why it matters

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Credit: Kirsten Colligan

Jamie Quinn
Science & Tech Editor

Science & Tech Editor Jamie Quinn on the danger of the growing scepticism of vaccines

We’ve all encountered someone in our lives that’s been royally freaked out by vaccinations. Be it a friend who just can’t stand needles or a hardcore anti-vaxxer, a certain fear of vaccinations exists in our society and the deadly consequences of this fear have been growing. We’re all in our own ways susceptible to the scare-tactics rolled out by the anti-vaccination lobbyists. When vaccinating my sister, my own parents were swept up in the MMR scandal, that anti-expert foreshadowing moment when disgraced doctor Andrew Wakefield convinced the entire country that the combined MMR jag could cause autism in children. Luckily my parents were doubly convinced of the benefits of vaccines and paid to have my sister vaccinated through three separate jags. Other parents chose to forgo vaccination entirely.

It seems the repercussions are only being felt now, 15 years after Wakefield first manipulated Britain. Speaking about the 807 cases of measles reported in England, Dr Mary Ramsay, Head of Immunisation at Public Health England, has stated: “The majority of cases we are seeing are in teenagers and young adults who missed out on their MMR vaccine when they were children.” This year alone over 41,000 people have been infected across mainland Europe, up from 23,927 in 2017, and 5,273 in 2016.

Why are vaccinations particularly important? Of course the benefit to the individual is clear: you’re extremely unlikely to catch whatever you’ve been personally immunised against. That’s pretty great in the case of MMR, with measles causing the most number of vaccine-preventable deaths in the world, mumps lowering sperm counts in 1 in 10 men, and rubella causing the horrendously avoidable congenital rubella syndrome in unborn children. As individuals, we can avoid these kinds of highly infectious and potentially deadly diseases through a couple of simple injections given in childhood. However, there are many people in our society who are unable to be immunised, perhaps due to age, vaccine contradictions, or deficiencies in the immune system caused by HIV/AIDS, chemotherapy treatments or bone marrow cancer. Thankfully there exists a type of immunity beyond vaccinations called herd immunity. When enough people are individually vaccinated in a population, a vulnerable person is effectively immunised, using the vaccinated collective as a barrier against disease transmission.

The percentage of people that need to be vaccinated to bring about herd immunity varies with how a disease transmits itself. In airborne viruses like measles, it’s estimated that 92-95% of the population should be vaccinated. For less easily transmitted diseases like Ebola, which spreads through bodily fluids, that figure is thought to be 33-66%.

It’s quite clear how dangerous the growing scepticism of vaccines is now, given that it only takes around 5-8% of a population to decide not to vaccinate themselves or their children against measles before we lose herd immunity and vulnerable individuals, through no choice of their own, are put at serious risk. This is known as a form of the free-rider problem in economics, where people who have no medical reason to refuse vaccination do so out of fear, mistrust, misinformation or group-thinking, therefore reaping the benefits of herd immunity while actively undermining the effect. It falls to the rest of the community to ensure they are sufficiently vaccinated so that the vulnerable individuals can be protected.

So what can you do? If there’s nothing stopping you from getting vaccinated – particularly if you’re a Fresher – go sign up for the clinic and grab yourself a MenACWY vaccine, protecting you (and others) from a few strains of meningococcal bacteria that might otherwise lay you out with meningitis or septicaemia. While you’re there, you might want to check you’ve had your two rounds of MMR vaccinations. Together they usually last around 20 years, so if you went through school in the UK recently and received the jabs, you’re probably fine. Vaccines against diptheria, polio and tetanus are also on the government’s recommended list, but most UK nationals should have received these in school.

And before you consider skinny dipping in the Kelvin, I’d recommend checking your tetanus – there’s a bunch of sharp trolleys that hurt like a bitch.