COMPARISON OF DIAGNOSTIC ACCURACY OF SELF-REPORTED VARICELLA HISTORY WITH SERUM ANTI-VARICELLA-ZOSTER VIRUS IGG AMONG HOSPITAL HEALTHCARE WORKERS, SAMUT SAKHON PROVINCE, THAILAND (SEPTEMBER - OCTOBER 2020)

Abstract

Varicella outbreaks in hospital settings can cause severe or  disseminated disease in immunocompromised patients and vaccination of health care workers (HCWs) who lack evidence of immunity is recommended  to prevent and control such outbreaks.  We reviewed questionnaires from pre-vaccination protocol and result of varicella immunity from medical records of all HCWs aged ≥ 18 years who were enrolled in the varicella vaccination program at a secondary care hospital in Samut Sakorn Province, Thailand during September to October 2020.  Diagnostic accuracy of self-reported  varicella history compared with serum anti-varicella-zoster virus (VZV) IgG was evaluated among HCWs (n = 654; median age = 33 years, interquartile range = 26-41 years) with self-reported varicella disease history without  medical documentation or negative or uncertain varicella disease history.   Overall seroprevalence was 78.4%, which significantly increased with  increasing age (p-value <0.001).  Physicians had the highest seroprevalence and nurses the lowest.  Among HCWs with self-reported history of prior varicella disease (n = 264) and with a negative or uncertain history (n = 390), 4 and 33% had negative serology test respectively.  Self-reported history of varicella  disease showed 49% sensitivity, 92% specificity, 96% positive predictive value,  and 33% negative predictive value.  One in four HCWs had no detectable  anti-varicella antibodies.  In conclusion, a positive self-reported varicella  history was a good predictor of serum anti-VZV IgG while a negative or uncertain varicella history was a poor predictor and, thus, implementation of a policy of pre-vaccination screening for varicella for all hospital HCWs is recommended.