Dear colleagues,
I compared the rates of an infectious disease in two groups (vaccination
vs. no vaccination group). To estimate the vaccine efficacy, I fitted a
Poisson Regression model
with some (fix) covariates and age as time dependent categorical
covariate (time varying age bands ) to adjust for the aging of the
population (assuming a piecewice constant baseline hazard within the age
bands). Adjusted for all covariates there seems to be a time dependent
(increasing) effect of the vaccination. Now I want to test if this
heterogeneity in efficacy over time is significant (perform a test of a
trend over time). How to do that, please could anybody help me.
Thanks in advance
Bernd
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