Wow! Getting vaccinated protects against premature birth in the period PRIOR to when one actually receives the vaccine. I think this pretty much settles it and there's no need to try to rule out confounding variables.
So the proportion of extremely premature births in women "immunised" in the first or second trimester might be as high as 1.09% * 18,187 / ( 18,187 - 13,005) = 3.83%? For a better estimate, one would have to know how many of the 13,005 were "immunised" in weeks 25-27.
Are the categories extremely/very/prematurely nested, or mutually exclusive?
This is not new. I remember last summer a similar paper written by the American CDC. The same trick.
Wow! Getting vaccinated protects against premature birth in the period PRIOR to when one actually receives the vaccine. I think this pretty much settles it and there's no need to try to rule out confounding variables.
So the proportion of extremely premature births in women "immunised" in the first or second trimester might be as high as 1.09% * 18,187 / ( 18,187 - 13,005) = 3.83%? For a better estimate, one would have to know how many of the 13,005 were "immunised" in weeks 25-27.
Are the categories extremely/very/prematurely nested, or mutually exclusive?