I Didn’t Get My Flu Shot Because…
Honestly, I’ve never had one. Until I had children, it wasn’t even on my radar that a healthy, young person would or should get a flu shot.
I’m sure you have been told all the reasons why you *should* get an annual flu vaccine, but are you being offered any counter information that may include some of the consequences or risks associated with the procedure?
There have been several papers now dealing with a phenomenon of ‘reduced vaccine effectiveness’ in people who have had annual or yearly doses of the flu vaccine. It means that people who get the influenza vaccine every year have a higher risk of catching the flu, than people who don’t get the yearly dose.
In 2014, US investigators published a paper that examined the vaccine effectiveness over 8 seasons and found that the greatest level of protection was seen in individuals who were not vaccinated in the previous 5 years.
Persons who had frequent vaccination history had an efficacy of 24% compared to vaccinated people with no prior vaccination history, at 65%.
The study enrolled 7,315 persons aged 9 and over with medically attended acute respiratory illness (ARI) during 8 influenza seasons. Of those people, 14% had influenza A, 9% had influenza B; the rest had non-influenza ARI (so approximately 75% of cases did not have influenza).
A curious finding in my opinion is that a large number of persons with ‘medically attended ARI’ had actually been vaccinated against the flu. For example, of those who were 20-49 year olds, 38% of them had received the ‘current season’ flu vaccine, compared to 41% with no current season vaccine and no vaccine history. But looking at older adults, 50-59 years old and 60-69 years old, 54% and 67% of them had the ‘current season’ flu shot, respectively, compared to 28% and 18% with no current season vaccine and no vaccine history, respectively.
For even older adults ages 70-79, 82% of them reported having the current season flu vaccine, while in elderly adults over 80 years of age, 84% of them had the current season flu shot. Remember, everyone in the study had a ‘medically attended acute respiratory illness.’
One can make the case that an elderly, high risk person is more likely to get a flu shot overall, but with the current recommendation declaring that all persons should get an annual flu vaccine irrespective of their risk factors, it may be good to know that a high number of these ‘medically attended acute respiratory illnesses’ occurred in persons with a recent flu vaccine.
This study doesn’t really make the case that flu shots keep these people out of the doctor’s office as these are all medically attended acute respiratory illnesses. And some flu season flu vaccine matching is worse than others: according to this paper, the 2012-2013 influenza vaccine had a negative vaccine efficacy for those who had the current season shot and was a frequent vaccinee, adjusted to -7% efficacy, so worse than a completely unvaccinated reference person.
Read the paper here:
Impact of repeated vaccination on vaccine effectiveness against influenza A(H3N2) and B during 8 seasons.
That Study Isn’t Alone
Several other studies (one in 1999 and another in 2015) came to similar conclusions: the more you do it, the less effective it is.
Published in 1999, the paper “Variable efficacy of repeated annual influenza vaccination” attempted to answer the question of why people who get annual flu vaccinations have reduced protection against influenza.
“The hypothesis extends the idea that the closeness of the antigenic match between the vaccine strain and the epidemic virus is important for vaccine efficacy in first-time vaccinees, by also considering the closeness of the vaccine and epidemic strains to previous vaccine strains to determine how vaccine efficacy is modulated by prior vaccination.”
A 2017 paper… “explored the extent to which repeat vaccination effects may have contributed to suboptimal influenza vaccine performance during recent A(H3N2) epidemics in Canada.”
How Many People Actually Get the Flu?
I always find it so interesting the discrepancy between symptomatic and asymptomatic infections…
A 2018 study in Clinical Infectious Diseases estimate around 3.0%–11.3% of the total population get symptomatic flu every season. This is a statistical estimate and not based on direct observation. During the pandemic, we saw the influenza virus basically disappear, and yet SARS-COV-2, a completely different virus, continued to circulate. While it’s common to see one strain replace another strain of the same virus, as in Delta replaced Wuhan strain, and Omicron replaced Delta–we don’t normally see one distinct virus chase off another genetically distinct virus. Where did the flu go?
But one trait that is common for nearly all viruses–is their propensity to go unnoticed, a.k.a. asymptomatic infections.
Several studies have looked at asymptomatic infections (the fraction of asymptomatic infections in an outbreak setting) and found huge variability, some around 16%, others as high as 65%-85% go completely unnoticed!
Read the paper here:
Seasonal Incidence of Symptomatic Influenza in the United States.
How can that be? How can so many of these “infections” have absolutely no symptoms? Why would we try to prevent that? With something that could possibly do more hard? Could there be another explanation for the symptoms that only *some* people feel?
And here’s another study: a 2014 paper in the Lancet Respiratory Medicine journal found that 18% of unvaccinated people were infected with influenza on average every winter based on a four-fold titre rises in strain-specific serology, and the majority of these infections were asymptomatic!
On average influenza infected 18% of unvaccinated people each winter. Up to three-quarters of infections were asymptomatic and about a quarter of infections had PCR-confirmed disease. 17% of people with PCR-confirmed disease had medically attended illness.
Doesn’t it seem important to try to uncover the mystery of why some people’s infections are not asymptomatic? What contributes to symptomatic disease? How does the body benefit from fever, or excretion of mucus.
Flu Vaccine and Mortality
Why would our health agencies still recommend yearly flu shots when this produces a reduced vaccine efficacy overall and an increased likelihood of infection relative to seldom vaccinated? Well, one reason may be because they think it reduces a person’s risk of death.
The CDC website has many studies that support the recommendation to vaccinate everyone against the flu, and cites a meta-analysis style study that suggests flu vaccines are associated with a 31% lower risk of death from flu compared with those who were unvaccinated.
Drilling into that meta-analysis, I picked one study that controlled for at least some confounding, because there are fundamental difference between people who seek or don’t seek influenza vaccination, as well as those who die of influenza and those who don’t die of influenza.
Keep in mind the study was financially supported by the CDC, and its authors potential conflicts of interest include:
W. S. is a member of the data safety monitoring board of Merck and Pfizer. W.S. also serves as a consultant for NovaVax, Dynavax, Sanofi-Pasteur, GSK and Seqirus. A. E. received funding from AbbVie for RSV-related work. His institution also received funding from MedImmune, Regeneron and NovaVax. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
The 2017 study in question is titled: “Influenza Vaccination Modifies Disease Severity Among Community-dwelling Adults Hospitalized With Influenza“ and it reports:
Overall, vaccinated adults had a 52−79% reduction in in- hospital death and a 37% reduction in ICU admission (among those aged 18−49 and ≥65 years) compared to those unvaccinated.
A few things I find interesting: A person is considered unvaccinated if they don’t have recorded the current season flu vaccine, but they could have had the prior season’s vaccine and still be considered unvaccinated. Since we have so much information about immune blunting from previous vaccine doses I am surprised this is not considered confounding, since we can’t rule out whether past doses affected a person’s future resistance against infection from both influenza and non-influenza pathogens.
Also, they excluded any person who didn’t get “antivirals”–and Tamiflu is notoriously associated with death–another hidden confounding variable that isn’t considered or explained. Pneumonia was also less common in the flu-vaccinated, yet they don’t mention pneumococcal vaccination status–another confounding variable. If pneumonia was more likely in the unvaccinated, and pneumonia is associated with death, that could be an explanation for higher mortality among the unvaccinated. A person who is flu-vaccinated may be more likely to have received their pneumococcal vaccine. The fact that this isn’t explained or addressed is, well, inexcusable.
It’s hard to take numbers at face value, because people are not numbers.
For example, this prospective cohort study of the elderly found that influenza vaccination was associated with an unadjusted reduction in all-cause mortality during three flu seasons to be 50, 46 and 42% respectively, which then decreased to 14, 19 and 1%, respectively, following adjustment for confounders and differences in mortality between vaccinated and unvaccinated individuals following the influenza season.
Their conclusions:
Vaccination remains the most important measure for prevention of influenza complications in elderly people, although the effectiveness in reducing all-cause mortality in elderly persons is lower than previously thought.
I do appreciate that their outcome measure was all-cause mortality, because I suspect that if a person had received a flu vaccine that may introduce bias into subsequent medically attended events, and they would be less likely to be diagnosed with influenza or that influenza would be labeled as their cause of death.
Because so many cases of medical attended upper respiratory infections are not caused by influenza, it may be better in general to keep track of all-cause mortality.
Here is a 2016 study that looked at influenza vaccine status among patients admitted with pneumonia: Association between hospitalization with community acquired laboratory-confirmed influenza pneumonia and prior receipt of influenza vaccination.
Overall, 2767 patients hospitalized for pneumonia were eligible for the study; 162 (5.9%) were influenza positive.
A total of 794 (29%) patients with pneumonia were vaccinated during current influenza seasons. Compared with unvaccinated patients, vaccinated patients were older, more likely to be white and enrolled during the 2010–2011 influenza season.
There were 11 (1%) in-hospital deaths among vaccinated patients, and 20 (1%) among unvaccinated patients.
So the same proportion of deaths occurred in vaccinated and unvaccinated patients, regardless of pathogen type. If the flu vaccine is supposed to reduce overall mortality–it isn’t apparent in this sample.
But How Does The Claim That the Flu Shot Reduces Death Relate To Mortality Surveillance?
Overall, since widespread flu vaccination has been encouraged, we have actually seen a higher influenza disease burden and mortality, not lower.
Interestingly, the first universal influenza vaccine recommendation did not come until the 2010-2011 influenza season. And since then, overall influenza disease burden has gotten worse, not better.
Just look at this graph from the CDC:
It’s typical for there to be seasonal fluctuations, but this is trending upwards, and cases, hospitalizations and deaths are not decreasing as would be expected to correlate with increasing vaccine coverage.
I wrote a while back about how flu deaths are increasing, not decreasing, since flu vaccines are being pushed more often on vulnerable populations. So nice try, Big Pharma.
How about you decide what is best for you and your family, but please don’t take the public health initiatives at face value. Look behind what they’re saying, and dig a bit deeper into the data, because it really makes no sense!
ADDITIONAL READING:
SOURCES:
Impact of Repeated V—n on V—e Effectiveness Against Influenza A(H3N2) and B During 8 Seasons, 2014
