Simulation parameters Mean of absolute difference (maximum) α σ CPa/FEb versus GEEc -5 1 0.0081 (0.0671)   1.5 0.0086 (0.0873) -6 1 0.0064 (0.1576)   1.5 0.0080 (0.1931) -7 1 0.0060 (0.1175)   1.5 0.0099 (0.2884) -8 1 0.0068 (0.2174)   1.5 0.0127 (0.3393) aCP, conditional Poisson model. bFE, fixed effects model. cGEE, generalized estimation equations.

Table 3: Mean of absolute difference of vaccination effect coefficient (maximum) from 1000 simulations with true β1=0.693 when individual-specific random effects have a normal distribution.