Vaccine-preventable disease experts say the severity of Canada’s situation will depend to some extent on chance.Andrew Testa/New York Times News Service
A surge in measles cases worldwide, declining vaccination rates, and one of the busiest travel seasons of the year have many medical experts on high alert for an outbreak, preventing further spread of the highly contagious virus. We are preparing an emergency response to stop it.
The World Health Organization’s measles expert said the coming months could test Canada’s vaccination system and expose potential weaknesses.
“This is where we will find out whether our immunization system is as good as we think it is,” said Natasha Crowcroft, WHO’s senior technical adviser for measles and rubella. She said, “Until measles spreads everywhere, just pretend that everything is okay.”
Nearly 20 confirmed cases of measles have been reported in Canada so far this year, but only 12 for all of 2023. Twelve of this year’s cases have occurred in Quebec, where community transmission of measles has occurred in the Montreal area. Vaccination rates are low. Last week, British Columbia recorded its first measles case since 2019.
Health authorities have urged travelers to take precautions during the March holidays, given the increasing prevalence of measles around the world.
Measles recurrence is cause for concern, not contempt
Vaccine-preventable disease experts say the severity of Canada’s situation will depend to some extent on chance. If you get measles while traveling abroad, your risk is low if you live in an area where vaccination is well-established. However, if measles cases are introduced into unvaccinated areas or even hospitals with large numbers of immunocompromised patients, the situation can be more difficult to manage.
“It’s always kind of a lucky draw where the imported cases end up,” said Monica Knauss, medical director of the Immunization Program and Vaccine Preventable Diseases Service at the B.C. Center for Disease Control. Ta. She added: “The risk is even higher if imported cases enter an under-vaccinated population.”
According to the WHO, the number of measles cases worldwide increased by 79% last year, reaching more than 300,000 people. Experts say a combination of factors, including disruptions to vaccination programs during the pandemic, lack of access in low- and middle-income countries, vaccine hesitancy and anti-vaccination beliefs, are all part of the problem. There is.
How effective is the measles vaccine?
The measles, mumps, and rubella vaccine has an efficacy rate of about 95%, meaning that 5% of vaccinated people remain susceptible. Imagine if out of a group of 100 people, 95 are vaccinated and 5 are unvaccinated. Unvaccinated people are at risk of contracting measles, as are five people in the vaccinated group. If all 100 people contract the virus, five unvaccinated people and five vaccinated people are likely to become infected. Ultimately, 5.3 percent of the vaccinated group will become ill compared to all unvaccinated people.
susceptible to –
not vaccinated
Curly Weeks and John Sopinski/Globe and Mail,
Source: BC Center for Disease Control
How effective is the measles vaccine?
The measles, mumps, and rubella vaccine has an efficacy rate of about 95%, meaning that 5% of vaccinated people remain susceptible. Imagine if out of a group of 100 people, 95 are vaccinated and 5 are unvaccinated. Unvaccinated people are at risk of contracting measles, as are five people in the vaccinated group. If all 100 people contract the virus, five unvaccinated people and five vaccinated people are likely to become infected. Ultimately, 5.3 percent of the vaccinated group will become ill compared to all unvaccinated people.
susceptible to –
not vaccinated
Curly Weeks and John Sopinski/Globe and Mail,
Source: BC Center for Disease Control
How effective is the measles vaccine?
The measles, mumps, and rubella vaccine has an efficacy rate of about 95%, meaning that 5% of vaccinated people remain susceptible. Imagine if out of a group of 100 people, 95 are vaccinated and 5 are unvaccinated. Unvaccinated people are at risk of contracting measles, as are five people in the vaccinated group. If all 100 people contract the virus, five unvaccinated people and five vaccinated people are likely to become infected. Ultimately, 5.3 percent of the vaccinated group will become ill compared to all unvaccinated people.
susceptible to –
not vaccinated
Carly Weeks and John Sopinski/Globe and Mail, Source: BC Center for Disease Control
Canada eliminated measles in 1998. This means the virus can no longer spread naturally here. Cases are usually introduced through international travel. But if the virus persists here for more than a year, Canada will lose its measles-free status. It happened in 2011, after an outbreak in Quebec that infected nearly 800 people.
A 2012 study of the outbreak published in the Journal of Infectious Diseases noted that many of the cases were spread among students who had received one or two doses of the measles vaccine. But the WHO said overall vaccination coverage was below the 95% threshold needed to stop the virus.
The study concludes that given that a small number of vaccinated people are still susceptible to the virus, even if 3% to 5% of people remain unvaccinated, “a significant shift in the population’s risk of epidemics could occur.” concluded that this could be enough to push the country to a point.
Another large outbreak occurred in British Columbia in 2014. The outbreak was largely confined to religious communities that opposed vaccination. However, Dr. Knaus noted that thanks to the efforts of members and public health, the outbreak did not spread beyond the community.
He said if there is an outbreak in the area or in areas that are anti-vaccine, health workers can set up semi-secret vaccination centers where local residents can get vaccinated without anyone knowing. He said he has a lot to do.
“People who are members of the community didn’t want to come forward and be excluded from family and friends,” Dr. Knauss said, adding that establishing trust and maintaining communication with communities that refuse the vaccine. is essential for public health, he added.
Health officials say Canadians planning international travel should make sure their vaccinations are up to date. A person born before 1970 is thought to have immunity from the time when measles was prevalent in Canada, and he only needs to receive one dose to ensure immunity. there is. People born after 1970 need two doses to develop immunity. Officials are encouraging individuals to check with their health-care provider, but given that Canada does not have a national vaccine registry, it can be difficult to know who has been vaccinated. be.
Infants can receive their first measles vaccine at 1 year of age. Babies aged 6 months to 12 months can receive the vaccine if they travel abroad (but will need to be vaccinated again after 12 months).
Measles is one of the most contagious viruses in existence. Almost anyone who comes into contact with the virus will become infected unless they have been vaccinated or have immunity from a previous illness. There is no need to even be in the room at the same time as the infected person, as the virus can remain suspended in the air for up to two hours.
One in five infected people will require hospitalization. One in 10 people will develop complications such as pneumonia, and one in 1,000 people will develop brain inflammation, which can lead to serious problems such as hearing loss and intellectual disability. Up to 3 out of 1,000 people infected with measles will die.
That’s why health officials sound the alarm as soon as even a single case is reported, which is what’s happening in Greater Toronto’s York Region. On February 29, York Region Public Health announced a confirmed case of measles in an adult man in his 30s who had not recently traveled or had contact with anyone with measles. He was fully vaccinated and had mild symptoms.
As soon as the infection was confirmed, health authorities alerted about 1,800 close contacts to identify those most at risk of serious complications. So far, there have been no reports of infection.
An alert has been issued to inform the public of the places the man visited before being quarantined. Sarah Erdman, York Region’s deputy medical officer of health, said the health department has set up vaccine clinics and post-exposure prophylaxis clinics for high-risk groups. People who have been exposed to measles should be vaccinated within 72 hours or, for infants under 6 months old, pregnant women, and people with weakened immune systems, given blood that contains measles antibodies to prevent complications. It is necessary to inoculate the preparation.
Dr Crowcroft, who returned to the World Health Organization, said vaccination rates were falling around the world, creating a “perfect storm” of risks.
“We are in a really dire emergency for the rest of the world,” she said. “I can’t believe this is being taken seriously. Urgent action is needed now.”
