Poland(37) Chickenpox(29) Epidemiology(26) epidemiology.(11) varicella(9) 2019(7) public health(6) 2016.(6) 2014.(5) COVID-19(5) Infectious diseases(5) 2017.(4) 2012(4) vaccination.(4) 2020(4) hepatitis A(4) varicella.(3) hepatitis B(3) SARS-CoV-2(3) complications(3) 2015.(3) 2018(3) vaccination(3) hepatitis B.(2) HCV(2) SARS-CoV-2.(2) frequency.(1) Q fever(1) viral hepatitis A(1) health care personel.(1)