HOLES IN THE HERD

As public trust of vaccination decreases, deadly but preventable diseases will be on the rise

By: Karen Quinto

(written for Afexa Life Sciences)

 

If you’ve ever watched the Discovery Channel, you may have seen footage of animals traveling in herds. They keep the young, old, and weak members to the inside, surrounded by the stronger ones on the outside.

It’s called herd immunity, and it’s a clever trick that keeps predators from picking off the easiest targets.

Believe it or not, the population has the same type of strategy when it comes to immunity from deadly diseases.

Say the polio virus is the big bad wolf. If everyone around you has been vaccinated, you can still enjoy the benefits of immunity without being vaccinated. The disease will have a hard time spreading with so few vulnerable hosts to attack and will likely fizzle out.

But now, as more people opt out of voluntary vaccinations, holes in the herd are beginning to appear. Suddenly, the safety net we once enjoyed is not so strong. Deadly viruses that had once been all but eradicated may slowly creep back into the fold.

It may seem hard to believe the impact of these highly infectious diseases. You probably don’t know anyone who has died of measles, mumps or polio.

But you might soon.

Losing herd immunity

The flu may send you to bed for an entire week, but it isn’t worth vaccinating for — or is it?

“If you take vaccines, you would be less resistant to the flu,” says Shravya Gunda, a 19-year-old second-year biomedical engineering student at Ryerson University. “Back in India, I never had to take any shots and I never got any fever because I was resistant to everything. So, I don’t want to take the risk [of taking shots].”

This mentality is not uncommon as motivation to vaccinate is lower amongst most healthy people because of the individual’s perception of personal risk. In the journal Human Vaccine, a 2008-2009 study conducted to assess influenza vaccination among parents and guardians revealed that for every 23 babies vaccinated against H1N1, only one parent decides to get that same vaccination. Reasons included reimbursement, medicolegal concern and simply not getting around to it.

Dr. David Fisman of the Dalla Lana School of Public Health at the University of Toronto can attest to the waning effect of population immunity.

“What we’ve seen is a lot of parents have pulled back on immunization against childhood diseases, which lets these things take off again,” he says. “If you can imagine yourself in  that situation, it doesn’t take much to tip the balance to a point where these diseases that we’ve largely eliminated through immunization start to come back, and that’s exactly what has happened over the last five years.”

The autism scare

A scientific research that claimed to show a relationship between autism and vaccination spurred an anti-vaccination movement. The study, authored by Dr. Andrew Wakefield,  was later debunked, but the frenzy it created has proven difficult to reverse. Infant vaccinations continue to decrease and there is no telling how much of it was caused by the controversy it had ignited.

Dr. Fisman experiences the difficulty within his profession. Because vaccination is effective when nothing is happening, people tend not to appreciate the invisible benefits.

“You’ve got a lot of people looking around going, ‘Well, you know, I don’t see measles, I don’t see mumps, I don’t see rubella, and my kids could get autism if I get them vaccinated. So, for me, the balance of risks and benefits of getting vaccinated are all out of whack and I’m not gonna get them vaccinated,’” he says.

The problem is, herd immunity is essential for preventing the transmission of disease. The more infectious the disease, the larger the portion of the population vaccinated against it must be to confer immunity as a whole. Measles require at least 95% of the herd to be immunized to keep the virus at bay, but the levels are much lower than that even in  industrialized countries like Canada, Australia, England and New Zealand.

Is it worth it?

While the answer for some is an obvious ‘yes’, others face mental stigmas that discourage them from getting vaccinated, from lack of awareness to concern about side effects.

Some people, for instance, are horrified to find out that a ‘flu shot is made out of the same influenza virus particles it is supposed to protect against.  What they are unaware of is that the virus in the shot has been inactivated – damaged by chemical treatment and are no longer virulent. When it is introduced into the body, the immune system responds by making more B cells that are able to create antibodies. These antibodies tag the flu  particles for destruction by other immune system killer cells like neutrophils and macrophages.

Some people claim to be negatively affected by these dead viruses, but may have nothing to do with the virus itself.

“A lot of the side effects of the vaccines aren’t really about the actual immunogenic component of the vaccine,” says Dr. Emily Agard, an immunologist, science outreach educator and professor at Ryerson University. “[For example], it is the additives in the vaccines, like eggs, that some people might have allergies to. In any type of pharmaceuticals, there’s a possibility of side effects.”

In a sense, a vaccine acts like the body’s fire drill in case of a real emergency. It prepares the body for a real virulent attack by stocking it with enough soldiers to fight the good fight. This is what make vaccines so effective and yet so misunderstood at the same time.

(for the transcribed interview with Dr. David Fisman, https://karenquinto.com/blog-2/transcript-of-the-vaccination-interview/)

Photo: Elizabeth Fischer and Kim Hasenkrug, NIH

References

Toback S, Carr W, Hackell J, Bhatt P, Ryan A, Ambrose CS. 2011. Influenza vaccination of parents and guardians by US paediatricians. Human Vaccines. Vol. 7(4). 436- 40

Freeman, Scott. 2008. Biological science . 3rd ed. San Francisco: Pearson/Benjamin Cummings. Pg. 441

Alkuwari MG, Aziz NA, Nazzal ZA, Al-Nuaimi SA. 2011. Pandemic influenza A/H1N1 vaccination uptake among health care workers in Qatar: motivators and barriers. Vaccine. Vol. 29(11):2206-11.

Advertisements