Susceptibility to measles among healthcare workers: a cross-sectional serological study

To the Editor, Due to their job tasks, Healthcare workers (HCW) have a higher risk of exposure to measles than the general population. In a recent report in this journal from Patras, Greece, the authors raised concern when finding that only 50% of HCWs were completely vaccinated [1]. In Italy, epidemiological data from the Health Ministry reported that during the period 2017–2019 the vast majority of measles cases occurred among subjects who had no vaccination and a significant number of cases were reported among HCWs [2,3]. Here, we report on the susceptibility to measles of HCWs employed at the Tor Vergata Policlinic of Rome in terms of protective IgG antibody levels. We collected clinical records of HCWs who underwent annual occupational screening from 1 January 2019 to 31 December 2019. We excluded from the study, medical students since their occupational risk was not well established. For each patient, we recorded the following data: age, gender and IgG measles antibodies titer. Measles-specific IgG antibodies were detected by means of the LIAISONR Measles IgG assay that uses chemiluminescence immunoassay (CLIA) technology: a semi-quantitative evaluation of specific IgG antibodies was obtained. Serum IgG values higher than 16.5 AU/mL were considered protective. We divided the study population into two subgroups according to the age: below or over 35 years old. Among HCWs protected against measles infection, we compared the mean values of IgG specific antibodies between the two age groups through multivariate analysis. Statistical analysis was performed using SPSS software (release 24). p Values < . 01 were considered significant in our study. The study was approved by the Ethical Committee for Research in Human Subjects of the Foundation PTV, Polyclinic Tor Vergata of Rome (PTV). Clinical records of 378 HCWs (138 male and 240 female) were evaluated. The median age was 33.8 years (range: 25–70); 260 HCWs were in the 25–35 years group (102 males, 158 females), 118 were older than 35 years (36 males, 102 females). We found that 322 HCWs (85.2%) showed protective measles IgG antibodies values. Immune subjects in the age group 25–35 years were 79.2% of the sample, whereas in the 35-year old group 98.3% had a protective measles IgG levels (p< .001). Main findings are reported in Table 1. The average antibody titer of the sample was 183.8 AU/mL and we found no significant difference between male and female gender (179.4 vs. 191.6 AU/mL, respectively; p1⁄4 n.s.), whereas a statistically significant association between measles IgG level and age was detected (mean titer was 146.4 AU/mL for the age group 25–35 and 266.2 AU/mL among subjects aged 35-year old or more; p< .001). Our study aimed to evaluate the rate of serological protection among HCWs after the introduction of Italian national immunisation plan. We found a relatively high proportion of unprotected employed among subjects aged 35 years or less. The immunisation coverage found was far from the level of 95% considered by the WHO to be necessary to avoid the virus circulation in the target population. Due to their job task and to the general inadequate coverage, unprotected HCWs are potentially exposed every day to biological risks, working with infectious patients and coming into contact with contaminated fluids and materials: in this case, the vaccine may protect not only the HCWs but may also avoid the spread of the disease to susceptible populations. Younger HCWs were born in a period when measles