Tag: herd immunity

Challenging the Concept of Herd Immunity

Before we talked about clusters of unvaccinated children, experts warned about pockets of susceptibles.
Before we talked about clusters of unvaccinated children, experts warned about pockets of susceptibles.
The idea of herd immunity has been around since at least 1923 and became used to describe “the indirect protection afforded to individuals by the presence and  proximity of others who are immune.”

That’s not much different from how the CDC defines herd immunity today:

A situation in which a sufficient proportion of a population is immune to an infectious disease (through vaccination and/or prior illness) to make its spread from person to person unlikely. Even individuals not vaccinated (such as newborns and those with chronic illnesses) are offered some protection because the disease has little opportunity to spread within the community.

Also called community immunity, it is often misunderstood by folks in the anti-vaccine movement.

Challenging the Concept of Herd Immunity

That the idea of herd immunity is being challenged is not new.

“Along with the growth of interest in herd immunity,  there has been a  proliferation of views of what it means or even of whether it exists at all.”

Paul E. M. Fine Herd Immunity: History, Theory, Practice

If you get educated about vaccines and understand how herd immunity works, it is easy to refute these challenges, especially the idea that herd immunity isn’t real just because we still have outbreaks of vaccine-preventable diseases among highly vaccinated communities.

Why do we still have outbreaks then?

It is mostly because we live in open communities that don’t mix randomly.

Keep in mind that the best model for herd immunity is a randomly mixing closed community – “one in which the probability of contact within any time interval is the same for every choice of two individuals in the population.”

Again, that doesn’t mean herd immunity doesn’t work.

It just means we can expect to see some outbreaks when someone in a well vaccinated community visits another community with lower vaccination levels and more disease, gets sick, and returns.

“However,  within the population of a community,  there may be pockets of  susceptibles, either because prior epidemics have failed to spread into the group or because they have not accepted immunization.”

John P. Fox Herd Immunity

You must also consider the size of the community when thinking about herd immunity, for example, a family, school, neighborhood, or city, versus the entire state. So you can have herd immunity levels of protection at the state or city level because of high average vaccination levels, but pockets of susceptibles who live in the same neighborhood or go to the same school can mean that you don’t have herd immunity in those places, leading to outbreaks.

“Hib vaccine coverage of less than 70% in the Gambia was sufficient to eliminate Hib disease, with similar findings seen in Navajo populations.”

RA Adegbola Elimination of Hib disease from The Gambia after…

Lastly, there is not one herd immunity level for all diseases. It is a separate threshold for each and every disease, depending on how easily it spreads, how many people are already immune, how long immunity lasts, if there is a vaccine, and the effectiveness of the vaccine, etc. That means that a community can have herd immunity for Hib and polio, but not the flu, and for rubella and measles, but not pertussis.

What happened in The Gambia is a great example of herd immunity. After introducing a three dose primary Hib immunization schedule (no booster dose), rates of Hib meningitis quickly went from 200 per 100,000 to none. A few years later, there were 6 cases of Hib meningitis in mostly vaccinated children (no booster dose) and in the majority of cases, “close contacts had a history of frequent or recent travel to Senegal, a neighboring country with strong kinship links with The Gambia and where vaccination against Hib was not introduced” until the following year.

With a Hib meningitis rate of 3 per 100,000, they are still far below pre-vaccine levels of disease, and their situation doesn’t mean that herd immunity isn’t real, as you will understand once you review these myths about herd immunity.

Myths About Herd Immunity

What are some common myths about herd immunity?

  • that natural immunity is better than getting vaccinated. Not True. Natural immunity often comes with a price. Remember, many vaccine-preventable diseases are life-threatening, even in this age of modern medicine.
  • you can just hide in the herd. Not True. “Freeloaders” can gamble and hope that their intentionally unvaccinated kids won’t get a vaccine-preventable disease, but it won’t always work. There is a risk to “free-riding, in which individuals profit from the protection provided by a well-vaccinated society without contributing to herd immunity themselves.”
  • most adults aren’t immune because they haven’t been vaccinated or don’t get boosters, but since we aren’t seeing that many outbreaks, herd immunity itself must be a myth. Not True. Adults were either born in the pre-vaccine era and likely have natural immunity or were born in the vaccine era and are vaccinated and immune. But again, herd immunity is disease specific, so when we talk about herd immunity for measles, it doesn’t matter if they have immunity against hepatitis A or Hib. And adults get few boosters or catch-up vaccines. Also, some vaccines, like Hib and Prevnar, have indirect effects, protecting adults even though they aren’t vaccinated because vaccinated kids are less likely to become infectious.
  • most vaccines wear off too soon to provide long lasting protection for herd immunity to be real. Not True. While waning immunity is a problem for a few diseases, like pertussis and mumps, and you need boosters for others, like tetanus, vaccine induced immunity is typically long lasting and often life-long.
  • herd immunity wasn’t developed by observing immunized people, it was all about natural immunity. Not True. The first experiments about herd immunity by Topley and Wilson in 1923 involved vaccinated mice. Ok, they weren’t immunized people, but it wasn’t just about natural immunity! And much earlier, in 1840, it was noted that “smallpox would be disturbed, and sometimes arrested, by vaccination, which protected a part of the population.” That’s herd immunity he was talking about.
  • herd immunity is not a scientifically validated concept. Not True. It has been well studied for almost 100 years.
  • if herd immunity was real, diseases would be eradicated once you reached herd immunity levels. Not True. Reaching herd immunity levels simply starts a downward trend in disease incidence. A little more work has to be done at the final stages of eradication, like was done for smallpox and is being done for polio.
  • natural immunity causes much of the decrease in mortality from a disease in the developed world, even before a vaccine is introduced. Not True. While it is certainly true that there was a big drop in mortality in the first half of the 20th century for most conditions because of improvements in sanitation, nutrition, and medical science, it was not a consequence of natural herd immunity. And we continue to see significant levels of mortality and morbidity for many diseases in the modern era, especially for those that can’t yet be prevented by a vaccine, like RSV, West Nile Virus, and malaria, etc.
  • vaccines aren’t 100% effective, so herd immunity can’t really work. Not True. Part of the equation to figure out the herd immunity threshold for a disease takes into account the effectiveness of a particular vaccine.
  • folks with medical exemptions for vaccines put the herd at risk just the same as those who intentionally skip vaccines. Not True. Children and adults with medical exemptions, including immune system problems, those getting treatments for cancer, and other true medical exemptions don’t have a choice about getting vaccinated.

So, like other anti-vaccine myths, none of the herd immunity myths you may have heard are true.

That makes it hard to understand why Dr. Russel Blaylock goes so far as to say “that vaccine-induced herd immunity is mostly myth can be proven quite simply.” Does he just not understand herd immunity? That is certainly a possibility, because “although herd immunity is crucial for the elimination of infectious diseases, its complexity and explicit relationship to health politics cause it to remain under-explained and under-used in vaccine advocacy. ”

He is also really big into pushing the idea that adults have no or little immunity, because when he was in medical school, he was “taught that all of the childhood vaccines lasted a lifetime,” but it has now been discovered that “most of these vaccines lost their effectiveness 2 to 10 years after being given.”

The thing is, Blaylock graduated medical school in 1971, when the only vaccines that were routinely used were smallpox (routine use ended in 1972), DPT, OPV, and MMR (it had just become available as a combined vaccine in 1971). Of these, it was long known that smallpox, diphtheria, and tetanus didn’t “last a lifetime,” and the live vaccines OPV and MMR, except for the mumps component, actually do.

Blaylock, like most anti-vaccine folks who push myths about herd immunity, is plain wrong. And like most anti-vaccine myths, using herd immunity denialism to convince parents that it is okay to skip or delay vaccines puts us all at risk for disease.

What To Know About Herd Immunity Myths

Herd immunity is not junk science or a false theory. Herd immunity is real, it works, and explains how people in a community are protected from a disease when vaccination rates are above a certain threshold.

More About Herd Immunity Myths

Parents Who Regret Not Vaccinating Their Kids

My uncle got polio just before the vaccine was developed. He was hospitalized for six months, almost didn't survive, and lived with atrophied muscles in one of his legs.
My uncle got polio just before the vaccine was developed. He was hospitalized for six months, almost didn’t survive, and lived with atrophied muscles in one of his legs.

A rather strange anti-vaccine argument you might sometimes hear is that you can’t unvaccinate your kids (even though they push detox plans that say they do exactly that), so go ahead and wait to vaccinate them until you have “done your research” and are sure.

The problem with that argument, like most others that anti-vaccine folks use to justify their decisions to skip or delay vaccines, is that you can wait too long.

“In 1736 I lost one of my sons, a fine boy of four years old, by the smallpox taken in the common way. I long regretted bitterly and still regret that I had not given it to him by inoculation. This I mention for the sake of the parents who omit that operation, on the supposition that they should never forgive themselves if a child died under it; my example showing that the regret may be the same either way, and that, therefore, the safer should be chosen.”

Benjamin Franklin Autobiography

Tragically, Ben Franklin wasn’t the last parent to regret not vaccinating his child.

More Parents Who Regret Not Vaccinating Their Kids

Roald Dahl, who famously wrote Charlie and the Chocolate Factory, is less well known for having a daughter who died of measles. It was just before the measles vaccine came out, so he didn’t regret not vaccinating her, but in urging other parents to protect their children, he did seem to regret that a vaccine wasn’t yet available.

For many other parents, a vaccine was available that could have kept their kids from getting sick.

“In 1989, the Haemophilus influenzae type b vaccine was relatively new and not yet routine. I was aware of the vaccine’s availability, but, busy mom that I was, I had not yet made the trip to the health department to get the immunization for my two-year-old daughter, Sarah. I will always regret that bit of procrastination and the anguish that it caused.”

Peggy Archer

Some of them have shared their personal stories, including the parents of:

  • Abby Peterson‘s “pediatrician steered her away from vaccinating her daughter” against chickenpox and her mother, Duffy Peterson, now says that “she wishes she had questioned the doctor’s recommendations more forcefully.” Abby died of a chicken pox infection.
  • Emily Lastinger who was unvaccinated and died of flu.
  • After all seven of her unvaccinated kids caught whooping cough, this parent regretted not having them vaccinated.
  • Claire Noelle Bakke who got pertussis when she was five weeks old
  • Scarlet Anne Taylor who died of the flu during the 2014-15 flu season
  • this unvaccinated three year old who spent six days in the hospital (part of it in a slight coma, during which they weren’t sure he would survive) with Haemophilus influenzae type b epiglottitis
  • Abigail who was unvaccinated and died of invasive pneumococcal disease
  • these two unvaccinated kids who developed severe dehydration from rotavirus infections
  • Sarah who was unvaccinated and developed a croupy cough when she was two-years-old and ended up on a ventilator with Haemophilus influenzae type b epiglottitis
  • Ashley who died from the flu and had never gotten a flu shot
  • Evan who died of a vaccine-preventable disease because his mom was not told about the vaccine that could have prevented it

There is another group of parents who have regrets about vaccines. Those parents whose kids can’t be vaccinated (too young to be vaccinated, have cancer, or have another medical exemption, etc.) are put at risk and exposed to vaccine-preventable diseases by intentionally unvaccinated kids. These parents typically regret that those around them don’t get vaccinated and protected.

Your decision to get educated and vaccinate your family shouldn’t be based on fear or concerns of regret if you delay or skip any vaccines, but these types of personal stories are important to review, especially if you also hear, watch, or read any stories about vaccine injuries.

What To Know About Regretting Not Vaccinating Your Kids

Delaying or skipping one or more vaccines isn’t safer or healthier, it just puts your child at increased of catching the vaccine-preventable diseases the vaccines protect you against and might lead to feelings of regret if you wait too long.

More On Parents Who Regret Not Vaccinating Their Kids

5 Myths About Tetanus and Tetanus Shots

Think you know everything you need to know about tetanus and tetanus shots to make an informed decision about getting vaccinated?

Unfortunately, there is a lot of misinformation out there about tetanus that can scare you away from getting a tetanus shot or make you think that you don’t really need one.

You can only get tetanus from a rusty nail. (False)

Would a rose smell as sweet if you pricked your finger on a thorn and got tetanus?
Would a rose smell as sweet if you pricked your finger on a thorn and got tetanus? Photo by Cherrie Mio Rhodes. (CC BY 2.0)

Tetanus is caused by the Clostridium tetani bacteria.

Unlike most other vaccine-preventive diseases, tetanus is not contagious. Instead, you can get tetanus after being exposed to tetanus spores in dust, soil, and feces, which then grow and make a powerful neurotoxin. Tetanus spores can even be found in the mouth of many animals.

So why does everyone associate tetanus with rusty nails?

We likely think that an old, rusty nail  is more likely to be contaminated with tetanus spores simply because it has been outside for a long time. Especially as compared to a brand new one that you just took out of a box.

But tetanus is not just about nails.

You can get tetanus after a cat or dog bite, a burn, frostbite, a tractor falling on your leg (crush injury), or falling into a rose bush (puncture wounds from thorns), etc. Almost anything that can cause a non-superficial wound can cause tetanus, especially if the wound is contaminated with dirt, feces, or saliva.

A tetanus shot won’t help after you have already been cut, stabbed, or bitten. (False)

The reason we give the shot is because the tetanus spores take time to germinate.

We are not worried about tetanus bacteria on a rusty nail, cat teeth, rose bush, or on ones very dirty hands through which a clean knife went through.

It’s the tetanus spores on those things and everywhere else, because they are in dirt and dust. And then, after the spores germinate inside a wound, the C. tetani bacteria have to start producing the exotoxin that acts as a neurotoxin, which causes the symptoms of tetanus.

The tetanus vaccine is against this exotoxin.

Unfortunately, it only takes a very small amount of tetanus toxin to cause tetanus. That’s why you don’t get natural immunity after being exposed to tetanus, but you do after getting the vaccine. It would only take about 60 nanograms of tetanus toxin to kill a small child.

Once the spores germinate, start producing exotoxin, and the exotoxin finally reaches your nervous system, that’s when you will start having tetanus symptoms.

If a puncture wound bleeds a lot, then you don’t need to get a tetanus shot. (False)

Many puncture wounds do not bleed a lot, but those that do are still at risk for tetanus.
Many puncture wounds do not bleed a lot, but those that do are still at risk for tetanus. Photo by James Heilman, MD

You don’t need to get a tetanus shot if you have a clean, minor wound and:

  • you have completed a primary tetanus series (a minimum of 3 tetanus containing vaccines), and
  • your most recent dose of tetanus vaccine was within the past 10 years

For most other wounds, including dirty wounds, animal bites, and puncture wounds, etc., you likely don’t need a tetanus shot if you have completed a primary tetanus series, and your most recent dose of tetanus vaccine was within the past 5 years.

In addition to a dose of tetanus vaccine, if has been less than 5 years since their last dose or they are unvaccinated or incompletely vaccinated, then they might also need to get tetanus immune globulin (TIG).

How much the wound bleeds has nothing to do with whether or not you need a tetanus shot. After all, a bleeding wound is not going to flush out all of the tetanus spores that might have contaminated your wound, or at least you have no guarantee that it did. What if the bleeding was more superficial and there was a deeper puncture wound that you couldn’t see?

This idea likely comes from the fact that tetanus is an anaerobic bacteria, meaning that it can’t survive around oxygen.

Tetanus is a mild disease. (False)

Tetanus, which people commonly think of as “lockjaw” is hardly a mild disease.

According to the CDC, “Even with modern intensive care, generalized tetanus is associated with death rates of 10% to 20%.”

And tetanus will always be a problem – if you aren’t vaccinated.

Since tetanus isn’t contagious and the tetanus spores are in the dirt and dust around us, you can’t rely on the folks around you to get vaccinated and “hide in the herd” for this vaccine-preventable disease.

Some recent cases highlight this myth:

  • an unvaccinated 7-year-old in Australia who contracted tetanus through an open wound in her foot while playing in her family’s garden. She was in critical condition, remained in the ICU for a few weeks despite quick treatment, and will likely face months, if not years of rehab after being released. (2017)
  • an unvaccinated women who developed obstetric tetanus
  • an unvaccinated 6-year-old in Canada who developed tetanus symptoms 10 days after stepping on a nail (2015)
  • unvaccinated children in parts of the world where vaccines are not longer available, like Ukraine
  • an unvaccinated 7-year-old in New Zealand who developed tetanus after cutting his foot and was hospitalized for almost a month (2013)

Worldwide, there are still about 49,000 deaths a year from neonatal tetanus and 14,500 deaths in children and adults. The incidence of tetanus has dropped tremendously since 1980 though, as more and more people get vaccinated throughout the world.

There are easy, non-toxic ways to prevent tetanus.

This one is actually true, it’s called a tetanus vaccine.

It replaced the previous treatment for tetanus, giving folks tetanus antitoxin, a treatment which began in the late 19th century. The first tetanus vaccine followed soon after, in the early 1920’s. It became more widely used during World War II.

“I myself suffered a fairly severe and deep cut on my ankle from a freak accident a few years ago but the thought of getting a tetanus shot for the injury never even crossed my mind.  I simply soaked my foot and ankle in warm salt water a couple of times a day for about a week to ensure that it stayed clean and contamination free.

The injury healed up nicely and I never exposed myself to the toxins and lingering health problems that can and do result from a tetanus shot.”

The Healthy Home Economist

Of course, when anti-vaccine folks talk about ‘non-toxic’ ways, they mean holistic type treatments without vaccines or other standard medical treatments.

When they tell you to clean the wound and take “extra cod liver oil, natural vitamin C, lacto-fermented foods and plenty of bone broths,” they are basically saying to hope that you are lucky and you don’t get tetanus.

Not only is the tetanus vaccine not toxic, but it helps fight the toxin that tetanus bacteria could produce in a contaminated wound.

What about hydrogen peroxide or colloidal silver? Like simple cleaning, with a deep puncture wound, none of those things will likely get to the ‘bottom’ of the wound. If you have even seen a puncture wound, like when a child steps on a nail, there is not much to clean. The wound typically closes up as the nail or other object exits the skin. Even with other wounds, unless you surgically open and irrigate the wound, you likely won’t clean it well enough to get all of the spores out if they are there.

What to Know About Tetanus and Tetanus Shots

Keeping up-to-date on your tetanus vaccines, which might mean an early shot if you have a dirty wound, is the only way to avoid serious and potentially life-threatening tetanus infections.

More About Tetanus and Tetanus Shots

Who Is at Risk If You Don’t Vaccinate Your Kids?

Passive immunity doesn't last until 12 months, when infants get their first dose of the MMR vaccine, so they are at risk for disease.
Passive immunity doesn’t last until 12 months, when infants get their first dose of the MMR vaccine, so they are at risk for disease. Photo by Jamie Beverly (CC BY-SA 2.0)

Whenever there is a discussion about folks who intentionally choose to not vaccinate themselves or their kids, one of their arguments invariably is ‘why are you so worried if you and your kids are vaccinated?”

Here is an example:

“My argument is simple. If you are vaccinated, you should not have to fear an outbreak of any preventable disease. That’s what the vaccine is supposed to prevent, right? Therefore, why should anyone butt into someone else’s business and tell them they should vaccinate? If one and one’s dependents are vaccinated, why should they have to worry about my personal decision to not vaccinate?”

I personally don’t believe in vaccines

As most people understand, the argument is far from simple.

Who Is at Risk If You Don’t Vaccinate Your Kids?

There are many people who are at risk from those who are unvaccinated, including those who:

  • are too young to be vaccinated or fully vaccinated – remember, with the latest immunization schedule, kids don’t typically get their first MMR until age 12 months and their second until they are 4 to 6 years old
  • can’t be fully vaccinated and have a true medical exemption – this includes children and adults with some immune system problems, vaccine allergies, or other contraindications to getting one or more vaccines
  • were vaccinated, but later developed an immune system problem and their immunity has worn off – might include children with cancer, AIDS, those receiving immunosuppressive therapy after a transplant, or a condition that requires immunosuppressive doses of steroids, etc.
  • were vaccinated, but their vaccine didn’t work or has begun to wear off (waning immunity) – vaccines work well, but no vaccine is 100% effective

These are the children and adults that can be, and should be, protected by herd immunity. At least they can be when most folks are vaccinated.

“We want to create a ‘protective cocoon’ of immunized persons surrounding patients with primary immunodeficiency diseases so that they have less chance of being exposed to a potentially serious infection like influenza.”

Medical Advisory Committee of the Immune Deficiency Foundation

So while some folks who are against vaccines try to scare others about shedding, those who take care of kids with immune system problems and their families go out of the way to get everyone around them vaccinated so their kids aren’t at risk of getting a vaccine-preventable disease!

“…the increased risk of disease in the pediatric population, in part because of increasing rates of vaccine refusal and in some circumstances more rapid loss of immunity, increases potential exposure of immunodeficient children.”

Medical Advisory Committee of the Immune Deficiency Foundation

Tragically, not everyone has gotten the message, and we continue to see and hear about kids who are too young to be vaccinated or who couldn’t be vaccinated get exposed to those who got sick because they simply chose to not get vaccinated.

What to Know About Risks from the Unvaccinated

Intentionally unvaccinated children and adults put others at risk for vaccine-preventable diseases.

More Information on Risks from the Unvaccinated

Effectiveness Rates of Vaccines

We know that vaccines work.

But how well do they work?

Taken together, you have to say that vaccines work very well.

Remember, according to the CDC:

Vaccine efficacy/effectiveness (VE) is measured by calculating the risk of disease among vaccinated and unvaccinated persons and determining the percentage reduction in risk of disease among vaccinated persons relative to unvaccinated persons. The greater the percentage reduction of illness in the vaccinated group, the greater the vaccine efficacy/effectiveness.

They aren’t perfect though and some vaccines do work better than others.

For example, the MMR vaccine provides 99% protection (two doses) against measles, while the seasonal flu vaccine can vary from 10% to 60%, depending  on how well the flu vaccine matches the flu virus strains that are getting people sick that year.

Fortunately, most vaccines have over 90 to 95% effectiveness.

The exceptions, in addition to flu vaccines, are the mumps and pertussis vaccines.

In addition to problems with waning immunity, they have lower rates of effectiveness than most other vaccines:

That’s probably why we are seeing more outbreaks of mumps and pertussis among vaccinated children and young adults, although intentionally unvaccinated children and adults are also contributing to most of those outbreaks.

For More Information On Efficacy Rates of Vaccines:

Herd Immunity

Herd immunity or community immunity refers to the process in which all people are protected against a vaccine-preventable disease because most of the community is vaccinated.

For more information: