Effect of COVID-19 vaccination on platelet count. Forest plot for estimated ratios of geometric means with 95% CI for the effect on platelet count. Time points 1 week, 4 weeks, 5 weeks, and 8 weeks after the first COVID-19 vaccination are compared with T = 0 (baseline), ITP diagnosis is the comparison of patients vs healthy subjects, and other variables are reported as comparisons of yes vs no. *Percentage difference and 95% CI were calculated from the ratio of geometric means.