The drumbeat happens every year, echoing far and wide: It's flu season! Protect yourself and others -- get a flu shot right away! Roughly half of the population heeds the message and gets the shot.
The reality of the flu and flu vaccines can be found, but it's elusive. Once you find out what's really going on, you can't help but wonder why public authorities and provider groups keep pounding everyone to take these shots.
What we're told about the flu and flu shots
I got an email from my primary care provider. Here was the attention-grabber:
And here was the lead paragraph:
They go on to give lots of detail in an FAQ.
It's pretty clear: get a flu shot and you won't get the flu. It's not just my medical group; they all seem to say it, along with major pharmacies like CVS. The FDA is equally clear: "A flu vaccine can be given to anyone who wants to avoid the flu (persons over 6 months of age." The CDC pushes it hard:
The message is similar to "shovel the snow off your snowy walk, and you won't slip and fall."
The flu is awful!
The CDC makes repeated strong claims about how awful flu is and how flu shots protect you from getting the flu. Surely those claims are backed by solid data, gathered by some of the more than 10,000 employees of that organization.
First, the CDC collects and presents highly detailed data about what they call the "burden" of flu, by which they mean the number of people made ill, hospitalized or killed by it. While the numbers vary from year to year, the totals are massive:
For example, for the last flu season entirely unaffected by Covid, here are the annual numbers from the CDC:
The overall burden of influenza (flu) for the 2018-2019 season was an estimated 29 million flu illnesses, 13 million flu-related medical visits, 380,000 flu-related hospitalizations, and 28,000 flu deaths (Table 1)
Huge, right? It makes sense that everyone should be protected against these consequences of the terrible disease of flu.
Let's dig a little deeper into those catastrophically bad outcomes. Again, we'll use the CDC's own data.
First, let's look at the flu disease burden by age. The CDC, quite sensibly, presents these next numbers as a rate per 100,000, so that you can get how likely the outcome is to actually affect you.
For little kids, age 4 and under, the rate of catching the flu is a whopping 15,238 per 100,000 -- about 15% of little kids got the flu! For people aged 5 to 64, it was in the range 7- 12,000 for most older kids and adults; less for those 65 and older. Lots of people get the flu, around 10%.
With so many people catching the flu, it makes sense that the flu shot is pushed by health authorities. It's not rare, it's widespread! The numbers back it up.
What about all those hospitalizations and deaths?
While getting the flu, going to the doctor and even getting hospitalized aren't great, the thing you really want to avoid is death.
So what happens after you get the flu? For the vast, vast majority, not much. For young kids and older adults, only 0.1% end up in the hospital, and for most it's less than half of that. Death? The death rate for adults 18 to 49 is 1.2 per 100,000. That's a rate of 0.001%. The rate for younger people is even lower.
How the the flu rank among the other causes of death? The CDC has the numbers.
Flu ranks number nine out of the top ten, about the same as kidney disease. Things like accidents, strokes and the ever-present heart disease and cancer are way more dangerous. And the chart says "flu and pneumonia," without getting specific. Chances are it's mostly pneumonia. From another CDC data table, I find that the rate of death due to suicide in 2019 was 14.5 per 100,000. So the chances of dying from the flu or pneumonia were about the same as killing yourself!
But wait! Something's wrong! The deaths per 100,000 are listed as about 13, while we learned from the CDC (table 2 above) that the flu deaths for kids and adults per 100,000 were only about 1 -- truly tiny!
Putting the death rate for kids and most adults into the chart above, the rate of dying of the flu is less than one tenth that of the least likely of the top ten, way under 1% of dying from one of the top two causes. For kids and most adults, dying of the flu is not even close to being a leading cause of death.
Old people and the flu
Let's read the stats about flu burden by age (table 2 above) more carefully. Go down to the bottom and look at the numbers for older people, 65 and over. Only 4% of older people get the flu (way less than other ages), but for those who do, the rates of hospitalization and death are dramatically higher. Roughly 10% of those who get the flu end up in the hospital and 10% of the hospitalizations result in death! That's a mortality rate of 40 per 100,000. So it's the old people dying of flu (and pneumonia) that puts flu into the top ten causes of death! Without the old people, not only would the flu death rate not make the top ten causes of death, it would be less than 10% of the bottom cause, kidney disease! And way lower than other things such as accidents and suicide.
Let's understand the death rate for old people. Yes, it's forty times larger than the rate for most younger people. Scary, right? But running out the numbers, 0.4% of old people are hospitalized due to flu, and 0.04% of old people die of the flu. That's according to the CDC. Here's a chart from the CDC's annual report (a PDF file) of the leading causes of death for older people:
See flu and pneumonia there on the left? Pretty low on the list of things for older people to be worried about.
The charts for younger people are also interesting. For ages 10 to 24, accidents, suicide and homicide cause more than two thirds of deaths, while flu is less than a percent. For adults aged 25 to 44, flu is one percent, while for ages 45 to 64, flu doesn't even make the chart.
What about the flu shots?
The CDC and the rest of the health establishment may flash warning lights with loud warning sounds about the flu and how we need protection from it, but we now know that the numbers aren't compelling. But getting a flu shot isn't a big deal. shouldn't we get it anyway so that we're protected against the flu?
Flu shots: the CDC
First, let's look at the CDC's own numbers. They went to the trouble of assembling patient panels so they could get good numbers. The numbers have increased over the years; the recent 2018-19 panels are over 10,000 people. Here is the chart from the 2018-19 panel for effectiveness of flu shot against by age:
This is tough to make sense of at a glance. First, look at the top line, for all ages. 2763 people got the flu -- and almost half of them (48%) were vaxed! Meanwhile, 7249 people were flu-free, with a bit over half (56%) vaxed. Clearly, the vax didn't make much difference.
The numbers for older people are interesting. As we saw above, people 65 and older are the least likely to get the flu but the most likely to be hospitalized or die from it. The table shows that the older were far more likely than the rest to be vaxed, over 80%. But the number vaxed was nearly identical in the groups with and without the flu. Let's dig in.
The last column, CI (confidence interval) will be mysterious to most people. The CDC has an explanation in its section on vaccine effectiveness It's standard statistics. They give the effectiveness number based on a tiny fraction of the number of people who could get the flu. How likely is it to be the true value? The CI is the range of values it would be, with 95% statistical confidence. See the negative numbers in the far right for teens and adults age 50 and older? According to the CDC (and statistics in general) that means:
...if a confidence interval crosses zero, for example, (-20% to 60%), then the point value estimate of VE provided is considered “not statistically significant.”
Not only was the VE tiny, the number is effectively meaningless -- the flu vax could increase your chances of getting it, or decrease your chances. The CDC's main flu vax effectiveness ongoing study can't tell the difference! Which means ... getting the flu shot has no impact on whether you get the flu.
Flu shots: published controlled trials
There have been dozens of published controlled trials of flu vaccines in multiple countries. Reviews of the many trials have been conducted and published. This is an updated version published in 2018 of the prior review.
We included 52 clinical trials of over 80,000 people assessing the safety and effectiveness of influenza vaccines.
The effectiveness they found:
Inactivated influenza vaccines probably reduce influenza in healthy adults from 2.3% without vacination to 0.9% (risk ratio (RR) 0.41
"Risk ratio" is what is called the "efficacy" of the vaccine, normally reported as a percent; in this case it would be 41%. Most people when they read a number like that think it means they've reduced their chances of getting the flu by about 40%. Not so. Read the quote again: "2.3% of the unvaccinated got the flu, while 0.9% did get it." This means that most people didn't get the flu, whether vaxed or not. The study translates this into NNV (number to treat NNT, which is NNV for vaccines -- see this for an explanation)
71 healthy adults need to be vaccinated to prevent one of them experiencing influenza,
What about other consequences?
Vaccination may lead to a small reduction in the risk of hospitalization in healthy adults, from 14.7% to 14.1%
What do they conclude?
Healthy adults who receive inactivated parenteral influenza vaccine rather than no vaccine probably experience less influenza, from just over 2% to just under 1% (moderate-certainty evidence). They also probably experience less ILI following vaccination, but the degree of benefit when expressed in absolute terms varied across different settings. Variation in protection against ILI may be due in part to inconsistent symptom classification. Certainty of evidence for the small reductions in hospitalizations and time off work is low. Protection against influenza and ILI in mothers and newborns was smaller than the effects seen in other populations considered in this review. Vaccines increase the risk of a number of adverse events, including a small increase in fever, but rates of nausea and vomiting are uncertain. The protective effect of vaccination in pregnant women and newborns is also very modest. We did not find any evidence of an association between influenza vaccination and serious adverse events in the comparative studies considered in this review.
Makes you want to run right out and get the shot, doesn't it?
Flu shots: Huge UK study on older people
There was a massive study in the UK on the extent to which getting flu shots helps older people. This is the background they give:
Observational studies using traditional research designs suggest that influenza vaccination reduces hospitalizations and mortality among elderly persons. Accordingly, health authorities in some countries prioritize vaccination of this population. Nevertheless, questions remain about this policy's effectiveness given the potential for bias and confounding in observational data.
They studied adults aged 55 to 75 in England and Wales during 2000 to 2014. Here is what they found:
The data included 170 million episodes of care and 7.6 million deaths. Turning 65 was associated with a statistically and clinically significant increase in rate of seasonal influenza vaccination. However, no evidence indicated that vaccination reduced hospitalizations or mortality among elderly persons. The estimates were precise enough to rule out results from many previous studies.
Flu shots: are they harmless?
The data says clearly that flu shots don't do much good. But it's no big deal to get one, it might help, so why not? It turns out there are good reasons to avoid getting the flu vaccine, based on how vaccines work and supported by data. The CDC even explains some it, buried away.
Let's start with a little-discussed fact: vaccines do not in themselves prevent anything. Everyone has an immune system. Immune systems are amazing things. They fight against a huge variety of invaders to the body, defeating the vast majority of them most of the time. What vaccines do is "trick" the immune system into strengthening its defenses against a particular invader by sending things that look like the real attackers, except they've been neutered. Here's the issue: immune systems don't have endless defensive "weapons," so increasing defenses against one thing means decreasing them for others. Also the defenders aren't endlessly energetic. If they've been mobilized against an attack that doesn't occur, they don't have as much energy for the next mobilization.
This means that if you trick the immune system into shifting weapons for a threat and a different one occurs, the defense against the real attackers isn't as strong. This happens every year with flu vaccines as the variants change and particularly older peoples' immune strength fades. It also happens with covid.
Here is a summary of the most important studies.
The CDC has claimed that influenza vaccines do confer this benefit to older people. However, to support that claim, the CDC relies on observational studies that have been discredited by the scientific community.
In fact, as observed in a 2005 study in Archives of Internal Medicine (which is now JAMA Internal Medicine), despite a considerable increase in vaccination coverage among the elderly between 1980 and 2001, pneumonia and influenza mortality rates actually rose substantially. A 2008 review in Virology Journal similarly observed that “influenza mortality and hospitalization rates for older Americans significantly increased in the 80’s and 90’s, during the same time that influenza vaccination rates for elderly Americans dramatically increased.”
The effect of influenza vaccines on influenza mortality—much less their effect on all-cause mortality—was never studied in clinical trials, and later studies showed that the studies relied upon by the CDC to support its claim were fatally flawed due to a selection bias known as “healthy user bias”. In short, it wasn’t that elderly people who got a flu shot were less likely to die that flu season but that elderly people who were so frail that they were likely to soon die were less likely to get a flu shot. As a 2006 article in the International Journal of Epidemiology observed, the magnitude of this demonstrated selection bias “was sufficient to account entirely for the associations observed”.
In other words, there is no good evidence to support the claim of a mortality benefit of influenza vaccination for elderly people.
Unlike some vaccines, flu vaccines don't seem to do much active harm to those who get them. However, they do little to no good, and getting them repeatedly weakens your immune system, making you more likely to get the disease you are supposedly protected from. The fact that as more elderly people get the flu shot the more of them die of the flu is unsettling, to say the least. Doesn't sound like a boat I'd like to jump on to.
Conclusion
Why does the entire health establishment keep banging away at promoting flu shots? What is it exactly that causes the medical establishment to heavily promote treatments that not only don't help but can seriously hurt you? Things like diet, cholesterol, blood pressure and flu? If your goal is to promote trust in government and medical health advice, this is the last thing you should be doing.