New research suggests that measles vaccination protects against a wide range of diseases | Radio-Canada News

New research suggests widespread measles vaccination can protect communities against a wide range of other viruses and bacteria by preventing ‘immune amnesia’ – an unusual side effect of measles that scientists now believe leads to outbreaks of measles. other illnesses.

Measles vaccine dose last year.

In 2021, there were some 9 million measles infections worldwide, which resulted in 128,000 deaths and untold complications in children, including brain damage from encephalitis, according to the World Health Organization. health.

Declared “eliminated” from the United States by the Center for Disease Control in 2000, outbreaks have re-emerged in North America, including Canada, with outbreaks in 2019 seen in British Columbia and 22 states resulting in hundreds of case.

How “immune amnesia” works

“It’s a completely vaccine-preventable disease,” said Mansour Haeryfar, a professor of immunology at Western University in London, Ont., and vice-president of the Canadian Society for Immunology, which studies measles and his uncanny ability to sabotage human life. immune system.

Unlike COVID-19, one dose of measles vaccine is 93% effective in preventing the disease. The second dose increases its effectiveness to 97%. The vaccine is so safe and effective. It is often given to infants, with a booster at five or six years old, around the same time children are ready for public school.

By having their children immunized, parents not only protect them from a life-threatening disease, but they also protect them from an unusual side effect of measles called “immune amnesia” – a phenomenon where the virus impairs the immune system itself. even – causing him to quickly forget every pathogen he has encountered.

“Your immune system is basically in ‘default’ mode, like you’ve never seen a microbe or an infection in your life before,” Haeryfar said.

Scientists have known for more than a century that measles patients who die often do so from secondary infections, but Haeryfar said it wasn’t until 2018 that scientists understood why – the virus attacks immune system memory cells, erasing all information about our past exposure to pathogens, sometimes permanently.

“The measles virus can actually bind to these memory cells and wipe them out altogether. So that means you lose memory of your previous encounters with vaccines or microbes,” Haeryfar said. “To relearn this stuff, you will have to be vaccinated again.”

“You may need to be exposed to certain infections and you can build a memory, but there is a danger that as we get older our immune system won’t work like when we were young.”

Herd immunity against measles more important than ever

Haeryfar said the new understanding of “immune amnesia” underscores how crucial herd immunity against measles is because without it we leave behind pockets of our society that cannot be immunized for religious or religious reasons. health extremely vulnerable to more than measles.

“If you don’t have enough vaccinated people in the population, we will have an epidemic and the measles virus will continue to spread. It is a highly transmissible virus. The most transmissible virus you can imagine,” said he declared.

“If those memory cells are wiped out, you’re susceptible to unrelated infections, and if those unrelated infections are also highly transmissible, that leads to further outbreaks.”

In 2019, at least 90% of all children in Canada had received at least one dose of the measles vaccine, according to the Public Health Agency of Canada (PHAC). That same year, 96% of parents of 2-year-olds said they thought vaccines were safe, but nearly half said they were concerned about potential side effects from the vaccine.

PHAC said one in 10 parents believe alternative practices such as homeopathy or naturopathy can completely replace vaccines, despite numerous studies suggesting such practices put children at risk of serious illness.

Since then, the number of vaccine-hesitant parents may have increased, thanks to misinformation spread by anti-vaccine groups during the COVID-19 pandemic.

Measles is among the diseases in Ontario where children cannot attend public schools without proof of vaccination or without applying for an exemption for health or religious reasons.

Public Health Ontario (PHO) said the province was slightly below the national average in 2019 for measles vaccination coverage and has yet to compile data for 2020 and beyond, saying that new statistics will not be available before 2023.

Some local health units, such as the Middlesex-London Health Unit (MLHU), reported that estimated disease vaccination coverage for the 7-year-old cohort was at its lowest in 2020-21, increased slightly for 2021- 22, but remains below pre-pandemic rates.

Vaccine injuries in Canada remain extremely low. Between June 2021 and June 2022, the Vaccine Injury Support Program received 774 vaccine injury claims – only eight have so far been approved by the agency’s medical review board.