Vaccine reactions: How your “gut feelings” can fool you

The Pediatric Insider

© 2015 Roy Benaroch, MD

I’m struck, sometimes, by the vehement tone of some of the antivaccine comments you see out there. People who hate or distrust vaccines proudly proclaim that their Googling and life experiences have taught them that vaccines are bad. They don’t care what the science or the evidence shows. They know what they know.

Me? I’m not so much into vehemence and dogmatism. I’ll follow the evidence. Show me solid science that what I’m doing is wrong or harmful, and I’ll learn. I’ll let science—observations of the natural world—guide me, rather than what Facebook or Google or “my gut” says. Why? Because our guts can so easily be deceived.

A quick example: a baby gets vaccines, and five days later develops a health thing, like a life threatening allergy to peanuts, or a fever, or SIDS, or a rash, or a fussy night, or anything. The “logical” thing to do might well be to correlate one with the other. Baby got vaccine, a few days later something happened, so they’re related, right?

Wrong. Just because one thing follows another, one thing doesn’t cause another. In Latin, this is called the post hoc ergo propter hoc fallacy. An easy example:

My phone broke when I joined Netflix. So Netflix broke my phone. No, they’re probably unrelated. Phones break all the time, and people (used to) join Netflix all the time.

Babies in the first year of life have about 5 separate encounters for vaccines (it actually may be from 4-6, depending on timing and how the flu vaccine might be given, but we’ll just say “5”). So 5 of the 52 weeks of the first year of life – or about 1 in 10 — are, in fact, within a week following vaccines. Think about that. If anything bad happens in that week, and there isn’t another clear explanation, the bad thing may well be blamed on vaccines.

Statistically, about 1 in 10 babies who die of SIDS had a vaccine within the preceding week. That sounds scary, right? But in fact 1 in 10 ordinary, healthy babies from 0-12 months of age had a vaccine within the preceding week. There is no greater chance of dying of SIDS in the week following a vaccine than there is in any other week (in fact, vaccines are protective against SIDS—babies are less likely to die of SIDS if they’ve been vaccinated.)

Sometimes, a specific emotional story can frame a discussion. A friend of mine, a pediatrician, told me this story: his office was called at 4 in the afternoon by a mom who missed her baby’s 4 month well check appointment because their car broke down. No problem, she just rescheduled. But that night, her baby died of SIDS. That’s a terrible tragedy. What would the family had thought if that same baby had in fact gotten her vaccines that very day, and died that night? It was just a fluke that the car broke down. But you can imagine how the story might have played out on Facebook if the baby had been vaccinated that day.

And Facebook – we’re just beginning to realize how the expansion of social media is skewing our perception of the world around us. I’ve called this the “exaggerating freakiness” effect (I need to find a Latin phrase for that, or it will never catch on.) When an ordinary thing happens—and millions of ordinary things happen, every day—no one runs to the internet to post about it. But we love to post about the weird things, the unexpected things, and the one-in-a-million things. We don’t read about the millions of babies who get their immunizations without any problems. But we do read about babies who had issues after vaccines—whether or not the vaccines had anything to do with the problem. We can’t tell from Facebook posts whether one thing caused another, or even if the story is true. None of that matters. What we remember are stories that have emotional impact, regardless of what they mean about reality.

Parents do not need to worry about vaccines. They’re safe, they’re effective, and there is an extremely small risk of serious side effects—far outweighed by the good they’re doing keeping children and communities safe throughout the world. Don’t let headlines, click-bait, and emotional arguments trick you into worrying. Play it safe, protect your kids, and immunize.

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8 Comments on “Vaccine reactions: How your “gut feelings” can fool you”

  1. Mary Ann Kirby Says:

    Dr Roy, I am a Pediatric Developmental nurse of 50 years. I have seen devastating effects after some vaccines. I am not against them totally-but too many at once-at such young age age during critical bargain development is very dangerous. In predisposed children-I have seen the second MMR vaccine cause neurological damage-these kids- although standing in front of you-have basically left the planet. Mary Ann Kirby,R.N.


  2. wzrd1 Says:

    Well, there was *one* vaccine that was actually a fair amount dangerous.
    Thankfully, once the *super* dangerous disease was extinct, that vaccine was shelved and only given to specific traveling public health care workers, those working with that disease virus and the military and no others.
    The Smallpox vaccine actually was and is dangerous, just nowhere near as dangerous as smallpox and its 35% mortality rate.

    Liked by 1 person

  3. Dr. Roy Says:

    wzdr, you’re right, and hopefully smallpox will STAY gone (despite rumors of virus being held in labs that may not be secure. Scary world!)

    It sure would be nice to eradicate a few other diseases, like measles and polio. Polio is close to gone, though anti-vax propaganda and civil unrest in the developing world seems to have prevented complete coverage. WHO is still hopeful it can be eliminated completely. Measles is at least theoretically eradicable — it’s only transmitted by humans, and the vaccine is just about 99% effective — but in the current climate of hysteria and unfounded anxiety, it’s hard to image how we could stamp out the few remaining foci of infection.


  4. Dr. Roy Says:

    Ironically, Kirby tosses around anecdotes, perfectly illustrating the point of my post. “I say I’ve seen it happen. After A came B, so it must be the case that A caused B.”

    Liked by 1 person

  5. bilingualmom Says:

    My son started having seizures within 24 hours of vaccination with Dtap and two other vaccines. Not five days. 24 hours. And this is a common thread among parents whose children also had a reaction. And because of minor illnesses and me not feeling comfortable vaccinating him while sick (you aren’t supposed to, but some doctors will do it anyway!), he did not get any vaccines (after the Hep B at birth) until he was several months old. So for several months, he had multiple events that usually trigger a seizure in those susceptible to one (illness, fever). But no seizures. Not until he was vaccinated with Dtap several months later. What do your statistics say about that?

    Dr. Roy, you dismiss most claims of vaccine injury by saying it chalks up to post hoc fallacy. Here is the complete definition, from your own hyperlink: “Post hoc is a particularly tempting error because temporal sequence appears to be integral to causality. The fallacy lies in coming to a conclusion based solely on the order of events, rather than taking into account other factors that might rule out the connection.”

    So if the conclusion is based solely on the order of events, it is post hoc fallacy? What about when the conclusion is based not only on the order of events, but other factors like the fact that hundreds of other parents experienced the exact same type of medical event after their child was vaccinated with that particular vaccine? What about when the parent listens to the child’s doctor that it is just a “coincidence”, vaccinates the child again, and the child has a bad reaction again?

    With all due respect, I think you have gotten into the bad habit of automatically dismissing parents’ accounts of adverse reactions to vaccines as “anecdotes”. You do a grave disservice to your patients and their families when you cannot listen to what parents, who know their children much better than you do, are saying.

    And please remember that just because A does not necessarily cause B, does not mean that it doesn’t, either. What if we said that you can get lung cancer without ever having smoked, so that means that smoking does not cause lung cancer? Yes, some babies will die of SIDs, or have seizures, for other reasons. But they also die of SIDS and have seizures as a result of adverse reactions from vaccines.


  6. wzrd1 Says:

    So, you would have us ignore thousands of scientific studies and medical science, as “parents, who know their children much better than you”.
    Hence, you ignore the physicians, who know medicine infinitely more than you, in favor of your untrained, unschooled pseudo-observations.

    Our youngest child had SIDS, fortunately it was noticed early and with monitoring, she survived and is alive and well today, into her 30’s. No correlation was present with vaccines and the onset of SIDS, as is what modern medical science has also observed.

    You define a post hoc fallacy, then commit that fallacy. I’m uncertain if you cannot conceptualize the fallacy or if you’re willfully ignoring the fallacy as you commit it.

    Benign infantile epilepsy isn’t uncommon in infants and can be brought on by infection, stress and is still not extremely well understood. The epilepsy is usually self limiting and resolves in a year or two.

    Can some vaccines trigger a more significant reaction than usual in some children? Yes. Some people can even react with plain sterile water being injected. Some can be hypersensitive to a vaccine component or even the vaccine itself.
    I’d react with a low grade fever and malaise after receiving my military immunizations, about a dozen at once. I’d treat a handful of my men the following day for the same symptoms. After all, vaccines do trigger an immune response, some will react in a more robust way.
    But, which is worse, a self-limiting reaction or a disease, such as polio? Which is worse, infantile seizures that are self-limiting or measles, with its one in one thousand severe illness requiring hospitalization and one in two thousand deaths?
    Personally, I prefer a modest reaction to a life threatening disease. So does our medical professional daughter.
    But then, I’ve been present in the midst of polio and measles epidemics, once with both converging on villages at once. Far too many tiny graves were filled, I’ll not permit that horror to be brought back to our shores.

    Liked by 1 person

  7. bilingualmom Says:

    1) Please tell me how much time doctors spend specifically studying vaccines that is the reason they know “infinitely” more than parents who have studied the information available through the CDC and medical journals. I really would like to know, because from what I have heard from medical professionals, the information they are given in their training is pretty much how to administer them, what the schedule is, how to store them, and the basics of how they work. It is my understanding that they do not study the ingredients in each individual vaccine, adverse reactions and what they look like, the efficacy of each individual vaccine (because it varies by vaccine, of course – the flu and pertussis vaccines are on the low end of “effective”), who is more at risk to having a reaction due to allergies, medical history, or genetics, and how to screen children for those possible risk factors, etc, etc, etc.

    2) I defined the fallacy because it is based on coming to a conclusion based SOLELY on the order of events. In other words, if there are OTHER factors that ALSO lead you to that conclusion also, then it is not post hoc fallacy.

    3) “Our youngest child had SIDS…. and is alive and well today” How hypocritical you are. An anecdote is acceptable when it serves YOUR purpose. Apparently you also missed the part where I pointed out that just because some cases of SIDS are not caused by vaccines, does not mean that no other cases are not caused by vaccines. A little faulty thinking there. Remember my example of lung cancer sometimes not being caused by smoking, does not mean that many other cases of lunch cancer are not caused by smoking? By the way, my understanding is that SIDS – Sudden Infant Death Syndrome- is not diagnosed unless the child actually dies. It is the dying that makes it SIDS/ SUDS.

    4) I wouldn’t call my son’s epilepsy benign, as it has threatened his life on several occasions (he stops breathing), he has some mild learning delays, and he takes medication twice a day to keep seizures at bay. Pertussis is horrible for infants, but who knows what would have happened if he had been one of ones to contract it. We will never what could have been. But it IS possible to cure pertussis. My son’s epilepsy is never going to be cured.

    5) Yes, epilepsy can be triggered by infection, stress, and fever in those who already have the predisposition to it. I guess you also missed the part where I said that he did not have any seizures from birth to several months old, despite having illnesses and fever (actually, a high enough fever at 2.5 weeks that he was hospitalized). The seizures began within 24 hours of vaccination with Dtap. What a “coincidence”. Especially considering that the CDC lists seizures as a possible side effect in 1 in 14,000 children. Especially considering that thousands of people protested the previous version of the same vaccine (DTP) more than thirty years ago because so many kids were getting seizures from it, which is why they came up with the Dtap, because supposedly it is safer. I don’t even consider that 1 in 14,000 accurate, since adverse reactions to vaccines are so woefully underreported.

    6) While I understand that the measles epidemic that you witnessed was horrible to go through, please compare apples to apples. I think it is reasonable to say that “that horror” that you witnessed in a small village overseas, most likely in a population that did not have access to good nutrition, great sanitation, and/or medical resources, is not what measles epidemics used to look like here in the U.S. or would look like here if we were to ever have the same number of cases again. This is not to downplay it, but it is important to be accurate.

    You do what you have to do, but since I am the mother of a child who was permanently injured by a vaccine, I will also do what I have to do, which is push for legislation to make sure that adverse reactions are better reported, that doctors are held accountable for not following the law and not reporting serious medical events within proximity of vaccination, that manufacturers of vaccines be required to publicize the real risks that are associated with vaccines (just like any medicine that is advertised has to do), and that the public becomes aware of research showing the true efficacy of individual vaccines and that some vaccines (i.e. the pertussis vaccine) can actually turn a vaccinated person into an asymptomatic carrier of the disease.


  8. wzrd1 Says:

    I’m not going to bother numbering paragraphs or RaNdOmLy capitalize words or letters either, if you can’t figure out how to bold something, don’t bother with odd capitalization.

    Doctors study immunology during their training, that subject covers vaccines, something about immunization. Doctors also read studies, something about continuing education being required, besides, it’s really cool to keep up with one’s profession and new developments and studies.
    Random factors do indeed seem to occur, but are not purely actually related. That’s why studies are conducted and random events weighted and removed when found random. That’s why researchers conduct the studies and why peers review the studies, they’re trained in conducting the studies and peers savage poorly conducted studies. Again, your story is just that, observations conducted by someone with a bias toward the results.
    I answered an anecdote with an anecdote. Our pediatrician suggested possible SIDS when we observed that child blue and not breathing in her crib, he then had the hospital provide monitors the alarm when she stopped breathing in her sleep. Sleep apnea may indeed be one of the causes of SIDS, other risks are genetic, bedding, crib bumpers, sleep position and more. SIDS rates vary in developed countries from one in one thousand and one in ten thousand.
    Interestingly, a large study observed a decreased risk of SIDS with DTP vaccination.
    Pertussis is indeed terrible in infants, it can still be fatal with the best of care. Diphtheria is worse and a pseudomembrane can occlude the airway, heart and kidney problems can occur and bleeding can occur due to platelet depletion. Tetanus isn’t a dream vacation either.
    Sanitation has nothing whatsoever to do with vaccine preventable diseases that are droplet transmitted or transmitted by child sharing behavior. We’re not talking about cholera.
    Still, if you really want to research statistics, how about researching the morbidity and mortality rates of those diseases prevented or lessened by vaccines. That one in fourteen thousand drops by orders of magnitude.
    Again, measles has crap all to do with sanitation, it isn’t cholera, it’s airborne transmitted, or are you now claiming that we sanitize the air?
    Polio is oral-fecal, all of the sanitation in the universe won’t stop kids from contaminating themselves, hell, adults can’t prevent themselves from spreading norovirus far and wide!

    Yes, you do what you do, I’ll do what I do and raise merry hell until mandatory vaccinations are the law of the land.

    Oh, I left the smoking bit alone, as you were correct, even halon gas contamination of homes can cause lung cancer due to decay products.


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