Seroprevalence for measles among healthcare workers in Madrid, Spain.

Background: Immunity of healthcare workers (HCWs) against measles is a particular concern. They are more likely to contract it than the general population due to their occupational exposure which may cause a nosocomial outbreak.

Aim: To assess the measles immune status of HCWs at five Spanish university hospitals.

Patients And Methods: Serologic testing (IgG) for measles by chemiluminescence indirect immunoassay (CLIA) was carried out prospectively and consecutively in HCWs from five university hospitals. All HCWs were classified into four epidemiological groups: vaccinated individuals, those with a history of measles disease, subjects with no history of measles or vaccination, and those who did not know whether they had measles or were vaccinated, and into five professional categories: physicians, nurses, nursing assistants, other clinical workers and non-clinical workers. A logistic regression model was constructed to identify the factors independently associated with immunity to measles.

Results: The study group was composed of 2157 HCWs. 89% had protective antibodies against measles. Of the 238 non-immune HCWs, 199 (83.6%) had been vaccinated, compared with 1084 of the 1919 (56.5%) immune individuals (P<0.0001). The parameters significantly predictive of having protective antibodies against measles were: older age (P<0.0001), epidemiological status (P=0.0002, mainly past measles disease), and professional category (P=0.02, in particular nurses).

Conclusion: This study shows that HCWs, including those previously vaccinated, are currently at risk of measles and suggests that those with a natural history of infection are better protected. Therefore, knowledge and maintenance of immunity to measles are an essential part of infection control among HCWs.