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Judy Converse response to Orac blog concerning "Vaccination Status and Health in Children and Adolescents"

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Judy Converse response to Orac blog concerning Vaccination Status and Health in Children and Adolescents

I saw several questionable aspects in this study design. Haven't had time to read the comments so my apologies if these were already noted. (1) A control group many tens of times larger than the test (unvaccinated) group means that no particular trend can emerge. Doing this weakens the statistical likelihood of seeing the trend you are testing for. If getting equal size groups to test is impractical for some reason, then having twice as many controls as test kids is workable - but having many thousands more in the controls versus less than 100 kids in the unvaccinated group assures a weak finding if any. (2) The paper is vague on exactly what the vaccine records were. If kids got newborn hepatitis B shots, that usually resides only in the hospital (birth) record, and not in the pediatrician's office record. Were some of the unvaccinated kids actually vaccinated? It's not really clear - a potentially huge confounder. (3) It's a retrospective, not prospective design; considerably weaker (4) I see errors on kids' vaccine records in my practice regularly, which makes me further question the reliability of reviewing records and retrospectively at that (5) The German vaccine schedule is not the same as the US schedule, so we can conclude nothing about our schedule in the US from this (6) The authors appear at one point to lump "illness" all together, and count discreet illnesses like measles as they do chronic conditions like asthma, which is directly counter to the purpose of the study. Discreet infections like measles don't equate allergic illness/inflammatory conditions that last a lifetime. ... Long short this is a weakly designed study that looks like it intended from the outset to satisfy the bias of the authors.

Posted by: Judy Converse MPH RD LD | March 12, 2011 5:05 PM