Trend of immunity against measles and varicella zoster virus in healthcare workers in Korea.

OBJECTIVE

To examine the seroprevalence of measles and varicella zoster virus (VZV) among healthcare workers (HCW) and evaluate the concordance between self-reported history of previous disease or vaccination and seropositivity.

DESIGN

A seroprevalence study and survey.

SETTING

A university-affiliated tertiary care hospital.

PARTICIPANTS

All HCWs working in high-risk services in 2017 underwent serologic tests and survey; all new HCWs employed in the subsequent years, serologic tests only.

METHODS

A serologic study was conducted using chemiluminescence immunoassay (2017) or enzyme immunoassays (2018 and later). HCWs who underwent serological testing in 2017 completed a self-administered questionnaire on their history of infection and vaccination.

RESULTS

A total of 10,278 and 9607 HCWs underwent serologic tests for measles and VZV IgG, respectively, from 2017 to 2022. The overall seropositivity rates for measles and VZV were 78.1 % and 92.8 %, respectively. Measles seropositivity declined gradually from >90 % in the HCWs born in the 1960s to <80 % in those born in the 1990s. There was a significant difference in measles seropositivity between the birth cohorts (BCs) 1967-1984 and 1985-1999 (P < 0.001; odds ratio, 1.16; 95 % confidence interval, 1.14-1.18). The seropositivity for VZV was stable, at >90 % in all BCs. The self-reported vaccination history was not independently associated with seropositivity, and the negative predictive value of the survey was very low (9.6 % and 13.1 %, respectively).

CONCLUSIONS

Measles seropositivity showed a substantial decline among HCWs born in 1985 or later, while varicella seropositivity remained high. The self-reported vaccination history was not sufficiently reliable for screening HCWs.