Fig. 2.

Vaccine-associated side effects experienced after the first dose (N = 66 individuals). Side effects occurred more frequently in people with pre-existing immunity, particularly systemic symptoms. Fever or chills were not observed among patients without pre-existing immunity.

Univariate analysis for individual variables only revealed significant differences for “disconfort" and "shaking chills" (Fisher Exact Test two tailed p<0.05). Chi-Squared test (2 x N) analysis showed an overall significant difference in reactivity to vaccination between the experienced HCW and naïve HCW groups (p<0.001)