How can a lower still birth rate in ‘vaccinated’ pregnant women mean that they are at higher risk of a still birth? It is all about what stage of their pregnancy they get vaccinated – there is ‘survivor bias’ in those vaccinated late in pregnancy. The following analogy is based on one used by colleague Prof Retsef Levi. Suppose we want to find out whether runners in a 40 km (that’s 26-mile) marathon are more likely to finish the race if they are given a special vitamin drink during the race. To do this we set up a drinking station at 20 km where runners can pick up the drink if they wish. Suppose 200 runners start the race and we observe the following:
A very helpful analogy, thank you. Might there also be biases in women who take the vaccine being more educated (working against them in this case) and those who don't chose to take it being less well educated, wealthy, well nourished or smokers? These are not a randomised placebo controlled studies.
A very helpful analogy, thank you. Might there also be biases in women who take the vaccine being more educated (working against them in this case) and those who don't chose to take it being less well educated, wealthy, well nourished or smokers? These are not a randomised placebo controlled studies.
Jo
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