Shingles vaccine
Should I get it??
Not many a day goes by when I am not asked about whether to take a preventive treatment, make a diet/lifestyle change or get a vaccine.
Yes prevention matters.
Disclaimer: My practice is based on how researching different treatment and lifestyle interventions affect an individuals health. Population data and guidance are important, but since I treat individuals one at a time, I need to focus on how the treatment affects you, not your community, town or State. Population data is helpful for the forest view, but not always for the individual tree and root view.
A common vaccine I get asked about is Shingrix, marketed and used for preventing Shingles.
Here is an ad for the Shingrix vaccine
Ad looks impressive, but that is what advertisements are for.
90% effective sounds pretty awesome.
But is that actually true or perhaps a play on numbers??
Is the 90% efficacy the population (forest) or the individual (tree)?
BTW- There is a difference as we shall see.
When I look at any proposed treatment I want to first know how the treatment works and understand the mechanism of action.
I want to know if the treatment is safe.
I want to know how well it works for each individual (tree).
Knowing how it works in a population (forest) is fine, but as already mentioned I treat individuals (tree) one person at a time and I do not mind digging into and evaluating the roots, to see what makes it grow, or perhaps makes it sick.
To dive deeper let's look at prevention of Shingles using the Shingrix Vaccine.
There will be some math involved but no worries as I will be doing all the calculations. If there are any Math majors out there please feel free to correct my work if I messed up.
The trial included 13,900 people all 70 years of age or older, which are the people most affected by Shingles.
Shingrix vaccine was given as a set of injections spaced 2 months apart.
The trial participants were followed for a mean of 3.7 years following vaccinations.
There were 6950 participants in each group, labeled vaccinated or placebo.
Now let us look at the results through a common sense lens.
Of vaccinated participants, 23 out of 6950 developed Shingles over the 3.7 years.
Of placebo or non-vaccinated participants, 223 out of 6950 developed Shingles over the 3.7 years.
Those numbers may look impressive.
223 vs 23 - That is a big difference.
But remember there were 6950 people in each group.
Let's look at how many people from each group did not get Shingles.
Of vaccinated participants, 6927 out of 6950 did not develop Shingles over the 3.7 years.
Of placebo or non-vaccinated participants, 6727 out of 6950 did not develop Shingles over the 3.7 years.
Do the numbers 6927 vs 6727 seem as big a difference as 223 vs 23???
If we calculate the relative percentage risk reduction for Shingles in vaccinated participants, it comes out to about a 90% relative risk reduction, calculation below.
23/223= 0.10
(1 - 0.1) x 100 = 90% Relative risk reduction
This is what Big Pharma uses to make their numbers look so impressive. They take the population (forest) based approach to numbers as opposed to an individual (tree) based approach.
So now let us look at the numbers in a different manner. Let us look at the absolute percentage risk reduction for an individual (tree) and then calculate a number we call the NNT, Number Needed to Treat.
NNT is how many people you need to treat with an intervention to prevent one case of what you are trying to treat/protect against.
I find this more helpful in deciding upon treatments for individuals (tree)- meaning one person at a time- YOU! Calculation below.
223/6950 = 3.2% of unvaccinated participants developed Shingles over 3.7 years
23/6950 = 0.33% of vaccinated participants developed Shingles over 3.7 years
3.2% - 0.33% = 2.87% (This is the absolute percentage difference between the two groups)
So if you as an individual (tree) take the Shingrix vaccine, there is a 2.87% chance you will not get Shingles over the first 3.7 years from when you received the Shingrix vaccine.
2.87% is quite a bit different than 90%
This also means there is a 97.13% chance the Shingrix vaccine will not benefit you.
Let us now calculate the NNT (number needed to treat):
NNT is how many people you need to treat with an intervention to prevent one case of what you are trying to treat/protect against.
100 / 2.87 = 35
The NNT for preventing Shingles using the Shingrix vaccine is 35.
This means that 1 out of every 35 people who take the vaccine benefit by not getting Shingles over the first 3.7 years.
This also means that 34 out of every 35 people who take the vaccine do NOT benefit from the Shingrix vaccine in preventing Shingles.
Funny that the numbers are never presented to you or even healthcare professionals this way by Big Pharma. I wonder why????
One other caveat here.
The study only looked at people aged 70 and older who are at greatest risk of getting Shingles. They do not have large data on people younger than 70. Why? I believe so few people under 70 in a population get Shingles that the data would be more difficult to manipulate in their favor.
I hope I do not sound too harsh.
One more example.
If I told you a preventive treatment would double your chances of avoiding contracting a disease, I am sure you would probably want that treatment.
What if I told you the disease occurs in about 1 out of every million people?
So if you take the treatment, a vaccine or a daily medication, your chance now of getting the disease is 1 in 2 million.
Would you jump at the treatment?
Or would you take your chances with a 1 in a million risk?
The relative risk reduction is 50% (1 million / 2 million)
The absolute risk reduction is 0.0001 %
The NNT would be 1 million people to prevent 1 case.
Tricky tricky tricky math numbers………….
Let us now take this one step further.
Post-Herpetic neuralgia (PHN) is a painful nerve condition that can arise after you have had Shingles. The below numbers are from the above study and another study which included people 50 years of age and older.
From the NEJM study PHN occurred in 4 out of 8250 vaccinated participants or 0.04% or 1 in every 2062 people.
From the NEJM study PHN occurred in 36 out of 8346 non-vaccinated participants or 0.4% or 1 in every 232 people.
The NNT for PHN:
0.4% - 0.04% = 0.36%
100 / 0.36 = 278
The NNT for preventing PostHerpetic Neuralgia using Shingrix vaccine is 278.
This means that 1 out of every 278 people who take the vaccine benefit by not getting PHN over the first 3.7 years.
This also means that 277 out of every 278 people who take the vaccine do NOT benefit from the Shingrix vaccine to prevent PHN.
So when you look at the above numbers it should make you think.
Big Pharma advertisements always stress the numbers that look so good.
But they never show the numbers that are closer to reality for an individual.
When I look at a treatment I want to first know how it works.
I then want to know if it is safe.
I then want to know how well it works for each individual. Knowing how it works in a population is fine to know, but I treat individuals one at a time. I will repeat that as it is important. I treat individuals one at a time.
This individualized treatment approach is why I prefer to look at statistics of absolute percentages and NNT as opposed to only looking at Big Pharma’s advertised relative percentages.
Absolute percentages and NNT tell me more about individual treatment.
Relative percentages tell me more about a population based treatment approach.
Both are worthwhile to know and understand before deciding upon a treatment plan.
I believe this is just Common Sense Health and Wellness.
Comments are always welcome.
If I messed up any Math, please let me know.
The 3.7 year timeframe is central to your arguments.
Thanks for this “real” analysis of the shingles shot. It is appreciated. I find your articles very informative.