Junior health minister Nadine Dorries tweeted last night:
“If herd immunity existed, measles and chickenpox would have been wiped out years ago. There is no such thing as herd immunity”
But she’s incorrect. Here’s why.
Herd immunity exists
Throughout the pandemic, we’ve often heard people misinterpret the term “herd immunity” as shorthand for the idea that we should let the virus run unchecked through the population.
But as Paul Hunter, Professor of Medicine at the University of East Anglia explained back in March, herd immunity is simply “when a large enough proportion of a population are immune that an infection does not spread so easily or it can actually die out.”
So “herd immunity” refers to the outcome, not the route we might take to achieve it. Though the path we choose is obviously significant.
Dr Bharat Pankhania, Senior Clinical Lecturer with the University of Exeter Medical School says that, in theory, we can get herd immunity from an infectious disease by “either vaccinating, or allowing people to get infected and recover”.
He adds: “The concept of creating herd immunity by infection is similar to creating it by vaccination. The difference is that when you vaccinate, you are using tried, tested and extremely safe vaccinations.”
But regarding coronavirus specifically, Dr Pankharia warned in March that: “Trying to create herd immunity through Covid-19 brings in questions of safety. You can’t control infection spread to ‘high risk’ people. Therefore, some people who become infected will develop very severe illnesses, and some of those would die.”
Could herd immunity wipe out measles?
Despite Ms Dorries’ claim, it is possible to achieve herd immunity to measles. As the NHS website states: “If 95% of children receive the MMR vaccine, it’s possible to get rid of measles.”
Indeed, the UK did achieve “elimination status” for measles in 2015, but it was revoked by the World Health Organisation 2019 after an uptick in cases. It’s thought the reason for this was a low uptake of the second “booster” shot, which is needed to secure long-term immunity.
The Department of Health was contacted for comment.