Monday, June 08, 2015

VE Voodoo

VE is Vaccine Effectiveness - an estimate of how well a vaccine does (or does not) work. 

The VE for the 2014 - 2015 flu vaccine was 18% (with a 95% Confidence Interval of 6-29%); 

Perhaps I could have titled this one "How a Confidence Interval can be a Confidential Informant". 

In statistics, the Confidence Interval (or CI) is interpreted as giving the range within which we can be x certain (in this case, 95%) that the true effect exists. In general, the wider the interval between the two numbers the less certain one can be of the effect. The width of the CI is influenced by the sample size of the study - and in general the larger the study the smaller the width of the CI, providing greater confidence in the precision of the estimation of the effect in question. 

The CI associated with the CDC's VE for flu vaccines in the 2014 - 2015 influenza season is wide. It is unknown how large was the sample size used to generate the VE (this information is not provided). But if the sample size was large a wide CI is all the more concerning.  In their report they do at least acknowledge "reduced protection" and indirectly allude to the fact that even when the vaccine strain is well-matched to the circulating strain VE is about 50% at best. 

But then the last paragraph of the report contains this sentence: "None of the VE estimates by age for this season are statistically significant at this time." A polite way of saying that even the 18% VE may well be meaningless - that there may have been no statistically significant effect from the vaccine at all, or that it didn't work. At all. 

Given this information, how is it rational to demand healthcare workers use this product or risk losing their jobs? How can healthcare providers recommend this to a client? Why is the government and why are health insurers paying for this product? Why accept the risks of using this product when the odds of benefit are so slim (even IF the risk of harm is low)? 

No one should be forced to use a vaccine - nor manipulated, nor coerced in any way, shape, or form. Being threatened with loss of employment is a form of manipulation and/or coercion. Being threatened with not being able to go to school because you have not been vaccinated is likewise manipulative and coercive - it causes people to make a medical decision under an influence other than objective information and it introduces a third party into a relationship (and decision) that should be private. 

We deserve better - especially from people whose salaries we pay (ie: CDC officials). 

1 comment:

  1. Excellent points. It seems the data does not match their conclusion!

    Where have we seen this problem before?


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