## 2 Methods
### Potential Confounders  
Each subject's history was followed to evaluate the risk of stroke or to determine protective factors. Demographic characteristics (age and sex), comorbidities (e.g., diabetes, dyslipidemia, atrial fibrillation (AF) and Charlson comorbidity index [CCI]), level  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**Whole Cohort**} & \multicolumn{2}{c}{**Unvaccinated**} & \multicolumn{2}{c}{**Vaccinated**} & \\  & \multicolumn{2}{c}{**(_n_ = 59,521_)**} & \multicolumn{2}{c}{**(_n_ = 33,985_)**} & \multicolumn{2}{c}{**(_n_ = 25,266_)**} & \multicolumn{2}{c}{\(p\)**} \\ \cline{2-7}  & \multicolumn{2}{c}{_n_} & \multicolumn{2}{c}{**\%**} & \multicolumn{2}{c}{_n_} & \multicolumn{2}{c}{**\%**} & \multicolumn{2}{c}{_n_} & \multicolumn{2}{c}{**\%**} \\ \hline Age, years (Mean \(\pm\) SD) & \multicolumn{2}{c}{66,24 (8.24)} & \multicolumn{2}{c}{64.08 (8.19)} & \multicolumn{2}{c}{69.14 (7.37)} & \multicolumn{2}{c}{\(<\)0.001} \\
55–64 & 30,531 & 51.53 & 22,205 & 65.34 & 8326 & 32.95 & \\
65–74 & 19,122 & 32.27 & 7661 & 22.54 & 11,461 & 45.36 & \\ \(\geq\)75 & 9598 & 16.20 & 4119 & 12.12 & 5479 & 21.69 & \\ Gender & & & & & & \\ Female & 30,106 & 50.81 & 16,819 & 49.49 & 13,287 & 52.59 & \\ Male & 29,145 & 49.19 & 17,166 & 50.51 & 11,979 & 47.41 & \\ CCI & & & & & & \\
0 & 24,501 & 41.35 & 14,208 & 41.81 & 10,293 & 40.74 & \\
1 & 15,333 & 25.88 & 8699 & 25.60 & 6634 & 26.26 & \\
2 & 9613 & 16.22 & 5394 & 15.87 & 4219 & 16.70 & \\ \(\geq\)3 & 9804 & 16.55 & 5684 & 16.73 & 4120 & 16.31 & \\ Comorbidities & & & & & & \\ Diabetes & 13,422 & 22.65 & 7725 & 22.73 & 5697 & 22.55 & 0.600 \\ Dyslipidemia & 15,062 & 25.42 & 9087 & 26.74 & 5975 & 23.65 & \(<\)0.001 \\ Atrial fibrillation & 3726 & 6.29 & 1636 & 4.81 & 2090 & 8.27 & \(<\)0.001 \\ Anti-hypertension medications & & & & & & \\ Antihypertentives & 12,255 & 20.68 & 5343 & 15.72 & 6912 & 27.36 & \(<\)0.001 \\ Diuretics & 33,998 & 57.38 & 17,076 & 50.25 & 16,922 & 66.98 & \(<\)0.001 \\ Beta blocking agents & 31,978 & 53.97 & 16,696 & 49.13 & 15,282 & 60.48 & \(<\)0.001 \\ Calcium channel blockers & 44,966 & 75.89 & 24,277 & 71.43 & 20,689 & 81.88 & \(<\)0.001 \\ RAA & 40,146 & 67.76 & 21,659 & 63.73 & 18,487 & 73.17 & \(<\)0.001 \\ Co-medications & & & & & & \\ Statin drugs & & & & & & \\ \(<\)28 days & 38,564 & 65.09 & 22,849 & 67.23 & 15,715 & 62.20 & \\
28–365 days & 10,204 & 17.22 & 5829 & 17.15 & 4375 & 17.32 & \(<\)0.001 \\ \(>\)365 days & 10,483 & 17.69 & 5307 & 15.62 & 5176 & 20.49 & \\ Metformin drug & & & & & & \\ \(<\)28 days & 45,017 & 75.98 & 26,178 & 77.03 & 18,839 & 74.56 & \\
28–365 days & 4335 & 7.32 & 2677 & 7.88 & 1658 & 6.56 & \(<\)0.001 \\ \(>\)365 days & 9899 & 16.71 & 5130 & 15.09 & 4769 & 18.88 & \\ Aspirin drug & & & & & & \\ \(<\)28 days & 34,022 & 57.42 & 21,900 & 64.44 & 12,122 & 47.98 & \\
28–365 days & 12,351 & 20.85 & 6419 & 18.89 & 5932 & 23.48 & \(<\)0.001 \\ \(>\)365 days & 12,878 & 21.73 & 5666 & 16.67 & 7212 & 28.54 & \\ Level of Urban & & & & & & \\ Urban & 41,015 & 69.22 & 25,268 & 74.35 & 15,747 & 62.32 & \\ Suburban & 12,129 & 20.47 & 6158 & 18.12 & 5971 & 23.63 & \(<\)0.001 \\ Rural & 6107 & 10.31 & 2559 & 7.53 & 3548 & 14.04 & \\ Monthly income (NTS) & & & & & & \\
0 & 5709 & 9.64 & 2818 & 8.29 & 2891 & 11.44 & \\
1-20,100 & 19,825 & 33.46 & 10,282 & 30.25 & 9543 & 37.77 & \\
20,100–30,300 & 19,665 & 33.19 & 10,363 & 30.49 & 9302 & 36.82 & \(<\)0.001 \\ \(\geq\)30,301 & 14,052 & 23.72 & 10,522 & 30.96 & 3530 & 13.97 & \\ \hline \end{tabular}
\end{table}
Table 1: Characteristics of the Sample Population.  
of urbanization, monthly income and the use of various drugs (e.g., statin, metformin, aspirin), anti-hypertension medication (e.g., antihypertensive, diuretics, beta blocking agents, calcium channel blockers, renin-angiotensin antagonists) were obtained for all patients. Patients with prescribed <28 cumulative daily doses (cDDDs) of drugs were defined as nonusers [23].