I thought this was very interesting and thought I'd share:
From Section 12.1 of the Novartis 2009 H1N1 package insert:
Mechanism of Action
"...antibody titers (after) vaccination with inactivated influenza H1N1 virus vaccine have not been correlated with protection from influenza illness. In some human studies, antibody titer of ≥1:40 have been associated with protection from influenza illness in up to 50% of subjects."
What this says, in plain language, is that having an H1N1 antibody after getting an H1N1 shot has no correlation with not getting sick. And that a sizable antibody titer (of 1:40 or greater) only protects UP TO 50% of people from getting the flu -- meaning that the vaccine is a 50:50 deal at best for keeping you from getting sick.
To the OP it's great you are reading the insert but unfortunately your interpretation of the data has some false assumptions. Statistics is a subject that can be widely interpreted when only partial information is given. It is a large insert so there are further tables and such that I won't quote here but I'll explain some of these concepts.
First what is an Antibody titer. Basically it is a dilution so you number your first tube 1:1. Dilute that in half and then if you can still detect Antibody then you have a 1:2 titer. You keep going until you hit a dilution where you no longer detect antibody.
Here is an analogy, not exact. I give you a dole whip which lets say is real potent. Then I dilute it with half ice no additional flavoring. We are now a 1:2 Dole Whip, but I can still taste it. I do this again with another half ice. Now we are at 1:4 but because its really tasty I can still taste the Dole Whip. I continue on until sadly and after a quick cry I can't taste the Dole Whip.
Now this is
very important, the insert states that "In some human studies, antibody titer of ≥1:40 have been associated with protection from influenza illness in up to 50% of subjects." It does
NOT state that "a sizable antibody titer (of 1:40 or greater) only protects UP TO 50% of people from getting the flu." I am not sure where the "sizeable" adjective comes from, that's not really objective and concerning antibody titers doesn't describe any sort of adequacy from an immunological standpoint. Also the term greater needs to be used with caution because one has to remember you are dealing with the reciprocal of a number.
The insert statement means exactly what it says and if you read further in the insert it shows a trend that uses 1:40 as a data point for seroconversion.
Seroconversion means the development of detectable antibodies after immunization or exposure, in this case the H1N1 vaccine. For example in this case they found that some people with a titer of 1:40 have 50% protection (let's call it immunity from now on). You can't look at this as some 2-D entity one plane. There are some people that have immunity with a more dilute titer and some with a less dilute.
I'll use
another example of this concept, not an exact analogy just for the concept. For most people the grading system in a class A B C D F (A being the highest grade and F being a fail). And lets say there is a bell curve as well. Midway through the semester I show your report card to the class and it is a C and I say everyone that has a C has a 50% chance of passing this class and a 50% chance of failure. While this maybe true at this point there is more data to the question. People with a higher grade (A and B) have a higher chance of passing. People with equivalent grades (C) are in the same boat. People with a lower grade (D) have a higher rate of failure but remember if they keep a D they
still pass. So using C as a middle point of the curve there is a passing grade on both sides (ABCD)
Hypothetically if the company had chosen something like 1:100 as the titer and then told you that 90% of people have immunity at this level. This doesn't mean that 90% of people have protection. It sounds great, but there is not enough information in the initial statement. It doesn't tell you how many people have this level of titer (what if it is just one person), it doesn't tell you what population you are looking at, it doesn't give you any time frame, etc. That's the power of statistical analysis, it's all about what information you have and how you interpret the data.
If you read the whole insert there is a good amount of data there. I mean they even break it up into pediatric and geriatric populations. There is much more in-depth review that cold be had of the information so I am not claiming to explain it all. Whether it is peer reviewed I am not sure I didn't do these studies and I am not an Infectious Disease physician, I am just a quick look at this data. My point is that the company has no interest in making an overly long insert. They put exactly what they found data wise into it, there is very little interpretation there. Unfortunately they don't make things more clear in the insert but legally they don't have to, they only need to give the pertinent information. So it is difficult to make a global assumption that the vaccine is a 50:50 deal.
As a PP said as well, vaccines do not necessarily prevent all incidence of disease, while that is the goal often immunizations temper the outbreaks of disease and at least attempt to give a population an advantage against a possible outbreak. The most successful vaccine ever was the smallpox vaccine and I think that is the only case with 100% eradication.
Glad someone already pointed out that H1N1 is NOT the same flu being prevented by the flu mist.
Sorry for the long post but hopefully it makes some things clear.
) of strains there is always the possibilty of becoming infected even with the vaccine.
