Table 3. Statistical data concerning the level of antibodies to F1 Y.pestis among people have been vaccinated previously.

Months since vaccination	Odds ratio	95% confidence interval LL	95% confidence interval UL	p-value	Positive/negative results
12 months	3.8	1.6	9.4	0.003	38/241
8 months	7.2	2.8	18.3	0.0000	52/222
4 months	73.5	10.1	525.2	0.0000	91/184