Is there any connection whatsoever between getting a flu shot and getting the flu?

Factual Questions
1

I am not a conventional vaccine skeptic

In fact, I’d probably be classified by genuine vaccine-skeptics as a liberal doctrinaire pro-vaxxer who wants anti-vaxxers arrested, jailed, and castrated, in that order. My position on the COVID vaccine, for example, is “volunteer pin cushion” who will take a COVID booster any time they’re offered and who has never been less fully vaccinated than was possible. And I’m vehemently in favor of children being vaccinated against any and all childhood diseases, and I recommend vaccination to all of my lazy or moderately skeptical friends constantly. I’m something of a bore on that subject.

But here’s the thing: in the late 1970s, I took a flu vaccine, as was recommended to me, and about a week or ten days later, came down with the most miserable whopping case of flu known to man. I was in bed for a week, simply miserable, running a very high fever and suffering from classic flu symptoms as I never had before and never since. (I was in my early 20s at the time.)

I connected the two events in my mind. Plainly, I got the flu shot and soon afterwards I got the flu.

This made me skeptical about the efficacy of the shot but did not make me into a conspiracy-minded enemy of vaccines. What accomplished that was being told that I was crazy to associate the two events.

I was told (you can imagine) that there was no connection, that it was purely a coincidence, that any causality between the shot and the subsequent illness was statistically improbable to the point of ludicrousness, and that I was, in short, a nutjob to imagine that the one had anything whatsoever to do with the other.

Being so informed offended me. I found myself angry at having what seemed to me a rather obvious nexus invalidated and at being treated like an anti-scientific nutjob for connecting the two events.

I don’t know for sure that there is an explanation that would satisfy those who tried to explain what had happened but that wouldn’t have offended me. I like to think that such an explanation does exist. I just haven’t heard it.

And now that RFK jr has declared that he would not take a flu shot in a million years, I find myself in horrendously bad company, the worst company imaginable. But this Facebook short https://www.facebook.com/reel/2210560579469234 features a real scientist refuting Kennedy’s point. I’m no immunologist, so I have a little bit of trouble understanding the fine points of his refutation, but is he addressing my issue with the flu shot? In other words, I think he may be stating that there is a theoretical connection between getting the flu shot and getting the flu which MAY in rare cases result in the phenomenon that I insist happened to me (and that RFK jr insists happens regularly). Am I putting words into this scientist’s mouth, or is his explanation saying what I hope he’s saying, i.e., that there is a rare case of the flu shot leading to the flu, and I was just an unlucky bastard in 1978. I can live with that.

2

I’ve never gotten the flu or COVID in the same year I got shots for them.

3

Yes, there is a connection between getting the flu shot and getting the flu. If you don’t get a flu shot, you are much more likely to get the flu. Getting the flu a week or two after getting the shot is a coincidence. Humans are great at finding specious patterns from rare occurrences.

4

From my experience, the flu vaccine keeps me from getting the flu, but in some cases, it just means that if I do get it, I won’t be as sick as if I hadn’t had the vaccine. The same goes for the COVID vaccine, which I have gotten every year, and so far, I haven’t gotten COVID. Contracting a virus involves exposure, as well as how your immune system responds. A vaccine preps your immune system for the virus before you get it.

5

???

  • I get why it was frustrating for you to get a flu shot and then to get a terrible case of flu.
  • I get why it (very reasonably) seemed plausible to you that your flu shot and your subsequent flu infection were causally connected.
  • I get why you find it frustrating that nobody has a solid specific analysis on exactly what happened with your immune system and flu antibodies back in 1978, other than falling back on the most statistically probable explanation of “mere coincidence”.

What I don’t get is why this situation is offending and angering you to the point of making you sympathetic to antivax nutjobbery, even to a minor extent. Why can’t you just say “Yeah, it seems statistically most probable that the not-100%-effective flu vaccine I received happened not to protect me from the particular flu infection that I coincidentally encountered shortly afterward, although I’m keeping an open mind that there might possibly have been some statistically unlikely causal connection”?

In short: y u mad, bro?

6

I’m no immunologist either, but ISTM that this scientist is correcting Kennedy’s misinformation while acknowledging the existence of a real phenomenon called antibody-dependent enhancement of infection.

Antibody-dependent enhancement (ADE) of infectious disease is a phenomenon whereby host antibodies increase the severity of an infection. It is well established in viral infections but ADE also has an underappreciated role during bacterial, fungal and parasitic infections. ADE can occur during both primary infections and re-infections with the same or a related pathogen; therefore, understanding the underlying mechanisms of ADE is critical for understanding the pathogenesis and progression of many infectious diseases. […]

Antibodies elicited in response to an initial infection or vaccination can provide long-term protection against subsequent infections by exquisitely recognizing particular antigens and epitopes expressed by the infecting pathogen. Once bound to their target epitope, antibodies can elicit multiple protective functions, including pathogen neutralization, antibody-dependent phagocytosis, antibody-dependent cellular cytotoxicity, complement activation and enhancement of inflammatory responses. However, antibodies do not always protect the host, and antibody-dependent enhancement (ADE) of disease has been well described for dengue virus infections.

IOW (and IANAD, so take this with a large dose of salt), it appears to be well known that although vaccines do not give you an infection (except in quite rare cases of severe immunocompromisation or whatever), in some cases the antibodies elicited by vaccination can enhance rather than suppressing a subsequently acquired infection.

(Also, TIL that the ability of an algorithm or an organic substance to discriminate very finely among characteristics of different possible inputs is known as “exquisite recognition”, which was worth getting out of bed for all by itself. :slight_smile: )

7

The trick is to understand what getting an immunising shot does. It doesn’t stop you getting infected with the flu. What it does is prime the immune system so that it can short circuit some of the steps needed between being infected and your body being able to create an immune response that kills off the infection. Often this can mean you never notice the infection, but it might also just mean that you do get sick, but the infection never gets a good hold before you get well again. What is needed, is to prime your immune system with a specific antigen peculiar to the virus, which the system remembers and targets when it next sees it.

In the past some vaccines were made from attenuated (ie chemically damaged) viruses, and there was the small but real risk that they were not as attenuated as you might hope. This has long since past. Vaccines deliver a tiny fragment of virus particles, or just the antigen, and there is no viable component of the vaccine that can cause infection. Certainly no RNA, which is needed to actually replicate the virus. That is key, no viral RNA, no infectious agent present.

Flu vaccines are problematic in that there is usually more than one strain of flu doing the rounds, and only so many strains that the vaccine can protect against. Modern vaccines are quadravalent - ie can carry four strains. But in the past this was not so. The lead time needed to create a flu vaccine means that the expected virulent strain(s) has to be guessed at long before the flu season. Watching the strains doing the rounds in the opposite hemisphere can guide the choice. But it isn’t possible to get it right every year. So you can have the simple bad luck of getting immunised against a different strain of flu than is actually doing the rounds. In the past this was more the case, but even now, mutation of the flu can catch things out.

8

There are hundreds of influenza viruses and they mutate rapidly. Especially back in the 70s, predicting which ones were going to cause the problems in any one flu season was kind of a crapshoot:

[from the AI summary]

  • Predicting strains: To develop the annual vaccine, the World Health Organization (WHO) and other public health bodies analyze which flu strains are circulating globally. This information is used to predict which strains will be most prevalent during the next flu season.

This problem was demonstrated memorably in the 1976 Swine Flu “pandemic.” It was widely broadcast that H1N1, a variant of the strain that caused the notorious 1918 pandemic, would be very serious and the government recommended that everyone be vaccinated against it. But the WHO and CDC guessed wrong. Very few cases of swine flu showed up, and side effects from the vaccine became the big story. ( Swine influenza - Wikipedia ).

So yeah, you got vaccinated and it protected you against the strains for which the vaccine was effective, but you got unlucky and encountered a different flu virus that was going around.

I think the predictive models have improved over the decades, but it still isn’t 100% certain that a flu shot will immunize you.

[ed ninjaed by @Francis_Vaughan ]

9

It takes about two weeks for the flu vaccine to reach maximum effectiveness, so at week or ten days you had not reached that point.

10

I think this video sums up the link quite well…

11

Most flu vaccines work this way - using fragments of flu virus which cannot cause infection. An exception is FluMist, the nasal spray vaccine.

The situation the OP describes sounds like exposure to a flu strain not incorporated in that season’s flu vaccine, or a failure of the vaccine to cause an adequate immune response. But it wasn’t the vaccine giving the OP the flu, though it’s understandable the leap was made from correlation to causation.

In this situation I’m OK with the OP being a “vaccine skeptic”. With that caveat, I’m heartily sick of the news media calling full-blown virulent antivaxers like RFK Jr. “vaccine skeptics”. The term “skeptic” classically suggests someone dubious about certain things, but willing to entertain good evidence and change their mind. Antivaxers cannot be swayed - their brains are locked solidly into their beliefs and any countervailing evidence will be met by sullen silence, changing the subject and/or playing the shill card. “Skeptics” they are not.

12

This is fairly typicial vaccine skeptic thinking, I’m sorry to say.

13

There are still some common vaccines that are ‘live’-attenuated vaccines, chief among them is the MMR (measles, mumps, rubella) vaccine, as are varicella (chickenpox) and zoster (shingles), and by necessity most bacterial vaccines. The oral polio vaccine (OPV) is an attenuated active virus and actually works by infecting the recipient with a ‘harmless’ virus that replicates without pathogenic effects; however, during replication it can revert to the original form and be shed, potentially infecting non-immunized people, which makes it crucial to get as comprehensive vaccination of the population. as possible. The inactivated polio vaccine (IPV) is preferred and the standard in developed countries but in developing nations OPV is often used for ease of distribution and application.

Vaccines, even recombinant, mRNA, and fully deactivated vaccines are not completely without risk because although the vaccine cannot revert to a propagating virus there is always the potential for stimulating an excessive adverse immune system response (organ or systemic inflammation). However, modern vaccines of all kinds are evaluated through a rigorous three phase process of safety and efficacy trials before being released for general use, and even though adverse reactions can occur (like myocarditis from the COVID-19 vaccines) the incidence and mortality are far less than that of infection by the actual virus. Modern vaccines have a very high safety profile (i.e they protect vastly more people than they harm) and the risk of permanent illness or death from a vaccine is so low that you are more likely to be killed in the parking lot walking into a clinic or pharmacy to get the vaccine than you are from adverse efforts. Vaccination with ACIP-approved vaccines is literally safer than taking most over-the-counter medications and certainly safer than consuming unregulated supplements. (At least, the ACIP before it was recently gutted by the current political regime in the US; going forward look for recommendations from the Vaccine Integrity Project or the European Vaccination Information Portal.)

The other statements about influenza vaccines are entirely on point (although I believe the US CDC is going to a general recommendation of the trivalent vaccine for this season). The protective efficacy of influenza vaccines is great by initial inspection—usually somewhere in the 40-ish % range—but that is because the dominant strains for a season are informed guesswork by virologists based upon epidemiology data of the proceeding season in the opposite hemisphere (and have to be produced months in advance so projections may not be completely accurate). However, even partial protection is sufficient to significantly reduce the severity of illness and more importantly attenuate spread of the virus to protect people with weakeNed immune system for who vaccination has less effectiveness.

That is a salient point; you need to get vaccinated several weeks in advance of the peak of the season for maximum protection, not once you’ve heard about outbreaks on the news. You also don’t want to get vaccinated too early if a late-season peak is anticipated because immunogenicity of the influenza vaccines wane after 3-4 months. For people with compromised immune systems getting a ‘booster’ shot three months after the initial shot is often recommended.

Stranger

14

The OP is a perfect example of the “post hoc ergo propter hoc” fallacy:

a Latin phrase meaning “after this, therefore because of this.” The phrase expresses the logical fallacy of assuming that one thing caused another merely because the first thing preceded the other. In other words, it is the fallacy of inferring a causal relationship from a temporal one. For example, “the dog barked immediately before the power went out; therefore, the dog’s bark caused the power to go out.”

15

And are you sure its even the flu that you got? As we all know now, a coronavirus can be happily circulating at the same time and have symptoms that are similar enough to pass as the flu. Without labouring the point others have made, there are so many ifs and unknowns to get through and resolve before you are ready to ask the question of causality.

The only likely measurable connection i can see is that if you go to pharmacies, your doctor or hospital outpatients for your jab, then you are at a slightly elevated risk because that is where sick people tend to hang out.

16

I think you’ve probably heard it, you just don’t accept it. The incubation for influenza is pretty long, and it’s very possible to be infected, not know it, get the shot, become symptomatic, and conclude the shot made you sick. Logical, but also wrong.

17

Flaw in that video: It defines correlation as not involving causation. But plenty of times, when there is a correlation between two things, one really does cause the other. Just, not always.

18

On a statistical note - a single example of what might have been you getting the flu says nothing about the effectiveness of the vaccine you got.

Vaccines are tested on huge numbers of people.

19

Yeah the ‘Correlation is not causation!’ meme has really taken root among people who don’t actually know anything about statistics, but while that statement is technically true, correlation is an indication of some causal link even if it isn’t the one that is naively assumed (or else some systemic bias in the assessment), which is why we have statistical tests to assess the significance, covariance, and direction of potential causality.

Stranger

20

Here’s a fun book about correlation vs. causation, with numerous “charts” showing such:

Spurious Correlations, by Tyler Vigen

Example: Cosmopolitan magazine ad revenue vs. coal imports to Germany, correlation: 92.8%

One of my favorite quotes is from another excellent book, How to Lie With Statistics, by Darrell Huff. Mr. Huff points out that there is a positive correlation between the salaries of Presbyterian ministers in Massachusetts and the price of rum in Havana. The question that comes to mind is: Are the ministers supporting the rum trade, or benefiting from it?

Both books are available at Amazon.com, but I don’t benefit from their sale, i.e., there is no correlation.