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Measles Makes Your Immune System Forget Its Protections Against Past Illness

posted by Jason Kottke   Feb 14, 2022

Historically, contracting the measles has been linked to subsequent illness (and possibly death) from other causes. In the past few years, scientists have discovered why this is: measles causes “immune amnesia”.

Enter “immune amnesia”, a mysterious phenomenon that’s been with us for millennia, though it was only discovered in 2012. Essentially, when you’re infected with measles, your immune system abruptly forgets every pathogen it’s ever encountered before — every cold, every bout of flu, every exposure to bacteria or viruses in the environment, every vaccination. The loss is near-total and permanent. Once the measles infection is over, current evidence suggests that your body has to re-learn what’s good and what’s bad almost from scratch.

“In a way, infection of the measles virus basically sets the immune system to default mode,” says Mansour Haeryfar, a professor of immunology at Western University, Canada, “as if it has never encountered any microbes in the past”.

This re-learning process takes up to three years, which “around the time it takes infants to acquire immunity to everyday pathogens in the first place”. In the meantime…

It’s not surprising, then, that measles doesn’t just increase the risk of illness, but also death. In fact, childhood mortality from other viruses is strongly linked to the incidence of measles. The 2015 study showed that when childhood mortality in the UK, US, or Denmark goes up, this is usually because measles has become more prevalent.

The findings explain why vaccinating children against measles has the unexpected, beneficial side-effect of reducing deaths among children, way beyond the numbers who were ever at risk of dying from measles itself.

Of course, an extremely effective and safe vaccine offers protection against both measles and the immune amnesia it causes. But with the steep rise in anti-vaccination sentiment during the pandemic and the increasing willingness of conservative leaders to disregard public health protections in favor of “individual freedom”, widely vaccinating against this dangerous pathogen in the US & elsewhere will be more difficult than in the past.