Varicella zoster virus immunity in multinational health care workers of a Saudi Arabian hospital

Abstract

Introduction: The health care worker (HCW) is vulnerable to hospital-acquired varicella zoster virus (VZV) infection, and thereafter may transmit infection to coworkers and patients who are susceptible and hospitalized. Interventions to prevent varicella transmission in HCW groups of uncertain immunity prove labor intensive, costly, and disruptive. Therefore, documentation of total varicella immunity in HCWs is desirable.

Setting: The National Guard King Abdulaziz Medical City is a 600-bed tertiary care center in Riyadh, Saudi Arabia with a multinational staff.

Material and method: A program to assess the VZV status of HCWs was initiated in 1999. The survey was confined to HCWs having direct patient contact. Questions elucidated previous history of varicella (chicken pox) infection, antibody testing against varicella, and varicella vaccination. HCWs with a negative or unknown history were subsequently tested for varicella antibodies (IgG).

Results: Seventy-six percent (2,047) of the HCWs responded to the questionnaire. Of these, 562 (28%) were physicians, 761 (37%) were nurses, 438 (21%) were medical technicians, and 286 (14%) were involved in clerical work. A total of 802 (39%) were from the Middle East including Saudi Arabia, 633 (31%) were from the Far East, 361 (18%) were from the West and from temperate areas, 138 (7%) were from South Africa, and 113 (5%) were from other nationalities. A previous history of VZV infection was reported by 1303 (64%); 262 (13%) had a history of positive test for varicella antibody, and only 44 (2%) had a history of varicella vaccination. Of the 744 (36%) HCWs who had a negative or unknown history of VZV infection, 217 (29%) underwent antibody testing. Of these, 181 (83%) proved to be immune (IgG > or = 1.10), and 36 (17%) nonimmune (IgG < 1.2). The latter group have completed varicella immunization. Staff from the West (81%), Far East (78%), and South Africa (59%) reported more histories of VZV infection compared with the employees of Middle Eastern origin (46%) (P <.001) and disclosed a history of positive antibodies in 13%, 18%, 17%, and 8%, respectively (P <.001). In relation to occupation, nurses reported history of varicella infection (75%) and a history of positive varicella antibodies (16%) more than physicians (54% and 8%, respectively) (P <.05). Conversely, serologic immunity to VZV infection proved consistent among the different nationalities and among the 4 occupational groups.

Conclusion: Total varicella immunity of a multinational workforce can be realized through screening of HCWs and vaccination of susceptible individuals. It is preferred above repeated interventions after varicella exposure for its simplicity, cost-effectiveness, and efficiency. Knowledge of VZV infection varies between different nationalities and cannot be used as a true predictor of immunity. There is no difference in the immunity by antibody testing of staff recruited from temperate and tropical climates. Total varicella immunity should, therefore, be achieved through screening of all HCWs and vaccination of those susceptible.