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BEYOND LOCAL: How vaccines really work

Experts say that when vaccines are distributed properly, they will protect the individual and their community simultaneously
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It would be an understatement to call vaccines a hot-button topic in 2020.

Outbreaks of vaccine-preventable diseases are on the rise, and experts say the anti-vax movement is partly to blame. Misinformation about vaccines is so widespread that, in 2019, vaccine hesitancy was named one of the top 10 health threats by the World Health Organization (WHO).

Dr. Isaac Bogoch, clinician investigator at Toronto General Hospital Research Institute (TGHRI), told Global News that within the medical community, “there’s really not a lot of debate.”

“These are questions that have been answered decades ago: we know they’re effective, we know they’re safe, we know they’re available.”

There has been a resurgence of several vaccine-preventable diseases, but the most notable is measles, which killed 72 people in Europe in 2018.

“Measles is a very, very infectious illness, probably the most infectious illness that is vaccine-preventable,” said Dr. Kate O’Brien, director of the department of immunizations, vaccines and biologicals at WHO.

O’Brien told Global News there is one “fundamental reason” for the return of measles: “Not enough people are getting vaccinated.”

Here, Bogoch and O’Brien explain how vaccines work, what herd immunity is and more.

How vaccines work

Vaccines are issued through a needle, and depending on which vaccine you are receiving, it could take one or more shots to ensure you’re protected.

In each vaccination, there is a “killed or very weakened version of an infection,” said Bogoch.

“What happens is the person’s immune cells will respond to that killed or weakened version of an infection, [they] will recognize it and they will make certain antibodies that will recognize the killed or weakened version of the infection that was introduced.”

 

Then, the immune cells develop what Bogoch calls a “memory” of that infection.

“Fast-forward in time, and a person’s actually exposed to the real infection — that’s not weakened [or] not killed — and their immune system will have already seen it before,” he said.

“Their immune cells will already be able to produce the antibodies because that pattern has already been seen and recognized, and they’ll be able to fend off the infection.”

When they’re distributed properly and in high amounts, vaccines will protect the individual and the individual’s community simultaneously.

If an individual is exposed to an infection but they’ve been vaccinated for that infection, “they’re just less likely to get that infection,” said Bogoch.

According to Dr. Karina Top, pediatric infectious disease specialist and investigator at the Canadian Center for Vaccinology, no vaccine is 100 per cent effective in every single person, though effectiveness depends on the vaccine.

For example, “the vaccine for measles… we know about 95 per cent of people will respond to the vaccine, but that leaves five per cent who don’t,” Top previously told Global News.

“We recommend a second dose of the measles, mumps, rubella (MMR) vaccine to catch the people that didn’t respond [fully] to the first dose. That’s why, in Canada, we recommend two doses.”

And they’re even more important on the community level. “If 95 per cent of a population is vaccinated against measles [and] a case of measles is then introduced, it’s extremely unlikely for that infection to spread,” Bogoch said.

This is known as herd-immunity protection, which happens when enough of a population is immunized against a disease for those unable to be immunized (like a newborn infant) to be protected. For a disease like pertussis, a 94 per cent immunization rate is required, for example.

Ultimately, the issue of effectiveness is even more of a reason to be vaccinated.

“For anyone, child or adult, if you’ve been vaccinated and you still get infected, [you’re] going to be much less sick than if you haven’t had the vaccine at all,” she said. “You’re much less likely to end up in hospital.”

Ninety-nine out of 100 people who have had two doses should be immune to measles, mumps and rubella, Top said, but that still leaves one person for whom the vaccine may not completely work.

“That’s why we want everyone who can get vaccinated to get vaccinated — so we can protect that one person,” Top explained.

Health officials have identified a number of places across the country that are vulnerable to outbreaks because they have low herd-immunity rates. According to a 2014 Alberta Health Services presentation, those communities included Norwich (Oxford County), St. Catharines and Brantford in Ontario; the Lower Fraser Valley, Smithers and Vanderhoof in B.C.; and the Lacombe, Rimbey, Red Deer and Lethbridge areas in Alberta.

The anti-vax movement and other barriers to access

Droves of parents in Canada and around the world have joined what’s known as the anti-vax movement, opting not to vaccine their children for preventable but highly contagious diseases like diphtheria, tetanus, measles and mumps.

The fear is that these vaccines can cause autism — a claim made by a research paper published two decades ago that has since been widely discredited, and yet, some parents still aren’t vaccinating their children.

Misinformation like this persists, in part, because of social media and the internet.

“If anybody is in doubt and they start searching for information, it’s very easy to be pulled into reading stuff that really is anti-vaccine without knowing [because] it’s written in a way that’s very inviting,” said Dr. Natasha Crowcroft, chief of applied immunization research and evaluation at Public Health Ontario.

Crowcroft says anti-vax groups use narratives about parents making “informed health decisions” on their own, suggesting that doctors or the government should not be the ones deciding whether or not they vaccinate.

This is a form of veiled or coded language, Crowcroft says, as it pushes anti-vax sentiments in a subtler way than flat-out telling a parent to avoid immunization.

O’Brien from the WHO agrees the anti-vax movement is dangerous, but she’s worried about another reason people aren’t vaccinated: lack of access.

“When we look around the world, the main reason that outbreaks are happening is not because of vaccine hesitancy but because of lack of access,” said O’Brien.

“The lack of access can be that clinics aren’t open at the times and places when parents can go, it can be the fact that clinics are just simply not available in the communities and settings where people live.”

O’Brien thinks both vaccine hesitancy and lack of access need to be confronted when considering the causes of outbreaks.

“There are absolutely examples of outbreaks that are happening, especially in highly immunized countries, that are fully attributable or largely attributable to vaccine hesitancy and vaccine misinformation,” she said.

What’s next

O’Brien hopes to develop vaccines for those diseases that don’t currently have one to prevent them — like tuberculosis, HIV and RSV.

“Vaccines are one of the greatest and most impactful public health tools that we have,” she said.

Vaccinations ensure whole swaths of people “don’t have to suffer through a disease or through curative therapy,” instead offering them a chance at survival.

Bogoch’s priority for the future is the fight against misinformation about vaccines.

“The biggest risk [associated with vaccines] is a sore shoulder. These vaccines are extraordinarily safe,” said Bogoch.

“One of the big questions now in the vaccine world is how do we fight misinformation and pseudoscience that’s being peddled and amplified online? And what is a co-ordinated approach to this?

“These are completely preventable infections. There’s no reason for that.”

— With files from Global News’ Laura Hensley and Jasmine Pazzano

Meghan.Collie@globalnews.ca




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