Nosocomial transmission of chickenpox and varicella zoster virus seroprevalence rate amongst healthcare workers in a teaching hospital in China

Abstract

Background Varicella zoster virus (VZV) is a highly contagious herpesvirus with potential for nosocomial transmission. However, the importance of nosocomial chickenpox outbreak in China has often been ignored. With the increasing immunocompromised population in China, a thorough review of issues related to nosocomial transmission and the seroprevalence rate of VZV among healthcare workers is necessary. Methods Retrospective case finding for nosocomial transmission of chickenpox was conducted between January 1, 2013 and December 31, 2017. Cases were identified based on clinical features compatible with chickenpox. A cross-sectional study on the seroprevalence rate of VZV among healthcare workers (HCWs) was conducted between January 1, 2014 and December 31, 2017. The serum VZV antibodies of 1804 HCWs were measured by enzyme-linked immunosorbent assay (ELISA). The seroprevalence rate of VZV antibodies, the positive predictive value and negative predictive value of self-reported history of varicella were analyzed. The economic impact associated with nosocomial transmission of VZV was also assessed. Results A total of 8 cases of chickenpox were identified in three nosocomial transmissions, including 4 HCWs who were infected nosocomially. The overall seroprevalence rate of VZV was 88.4%, which significantly increased with age ( P < 0.01). The seroprevalence rates of HCWs with different genders and occupations showed no statistically significant differences. The positive and negative predictive values of a self-reported history of varicella were 80.8 and 10.6% respectively. An estimation of 163.3 person-days of work were lost in each nosocomial transmission and 86.7 infection control unit person-hours were required for each outbreak investigation. The cost of VZV IgG ELISA screening was estimated to be 83 USD per nosocomial transmission. Conclusions Nosocomial transmission of VZV occurred repeatedly in the hospital setting. An alarming 11.6% of HCWs were seronegative for VZV, which might increase the risk of nosocomial infection and outbreak for other susceptible co-workers and patients. This is especially important in the setting of a teaching hospital where many immunocompromised patients were managed. Furthermore, the positive predictive value of self-reported varicella on seroprevalence rate in our study was lower than those reported in other countries, therefore serological testing of VZV antibodies with subsequent vaccination for all non-immune HCWs should be considered.

Varicella Seroprevalence in Healthcare Workers at a Medical Center Following Changes in National and Local Hospital Vaccination Policies

“…VZV seropositivity was 90.63%, which is consistent with the 91.1% previously reported in Taiwan [7]. It has been reported that a group immunity of 94% or more is needed to interrupt viral transmission in the healthcare setting [2,13]. The study results showed a lack of VZV immunity in young participants 18–20 years of age, in whom nearly 15% were not seropositive.…”

“…In the absence of a natural booster, the protection provided by early childhood vaccination may decrease in adolescence and adulthood. That may result in an increase of varicella complications in addition to the risk HCW infection [2,6].…”

“…The varicella seropositive rate of the HCWs in this hospital was not high enough to prevent outbreaks. Evidence of immunity for HCWs includes one of the following: (1) written documentation with two doses of vaccine, (2) laboratory evidence of immunity or laboratory confirmation of disease, (3) diagnosis or verification of history of varicella or herpes zoster by a healthcare provider [2]. Confirmation of the VZV IgG status of all HCWs and the vaccination of those who are susceptible is recommended for effective prevention of nosocomial varicella infections.…”

“…It is important that the immunity of the hospital staff to varicella zoster virus (VZV) be monitored in order to decrease the risk of nosocomial infection and infection to the staff and visitors [1,2]. Varicella is highly contagious and spreads via respiratory aerosols or vesicle fluid.…”

“…Varicella is highly contagious and spreads via respiratory aerosols or vesicle fluid. It is usually self-limiting but may cause severe complications [2,3,4]. Approximately 11,000 cases of varicella are reported per year in Taiwan [5].…”