Selection bias: neighbourhood controls and controls selected from those presenting to a Health Unit in a case control study of efficacy of BCG revaccination.

None are statistically significantly associated with a second dose BCG vaccine in either control group, except that in the neighbourhood control group the association between owning a video and having a second BCG dose is of borderline significance, and the associations between ownership of other goods, although not significant, are in the direction expected – with the wealthier having a higher coverage.

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