The results of this study show that the prevalence of measles antibodies in HCW in Catalonia is higher than that found in other countries [11
]. A study in a New York tertiary hospital [11
] found a prevalence of 91%, and a Japanese study in which the majority of participants were tertiary hospital physicians found a prevalence of 92.6% [12
]. The specific characteristics of hospitals do not seem to be the main explanation for the differences between these studies and ours (which also included primary healthcare workers) because we found no significant differences in the prevalence between hospital and primary healthcare workers. Likewise, we found no differences between professional categories.
In Catalonia, as in other countries, vaccination of all subjects without documented evidence of measles immunity is recommended. Sufficient evidence is considered as birth after 1965 with a documented history of physician-diagnosed measles, serologic evidence of immunity or written confirmation of receipt of two doses of MCV [5
]. Adults born before 1966 are considered immune to measles, because the lack of vaccination and greater circulation of the virus resulted in near-universal exposure and the development of natural immunity [14
Susceptible individuals may be found in population cohorts born between 1965 and 1980, as some persons may have avoided measles infection due to the reduction in the incidence and because they were not vaccinated [15
]. However, this was not confirmed by the results of our study, as HCW from this age group had the highest prevalence of measles antibodies. Our results showed that the most susceptible group was HCW born after 1980, who should have received two doses of MCV. These findings are similar to those of Botelho-Nevers et al. [16
], and Seo et al., who suggested that, in younger subjects, vaccination coverage remained low [11
Although the objective of measles elimination in the European Region by 2010 was established, 120 outbreaks were reported throughout the region during the period 2005–2008, of which 17 had more than 250 cases, with 25 deaths [17
]. Currently, the goal of elimination has been renewed as 2015 [18
]. Therefore, improvements in vaccination coverage targeting all pockets of susceptible individuals and the early identification of and response to outbreaks are critical to achieving this target date for elimination in Europe [4
In some developed countries, due to the low incidence of measles in the last twenty years, exposure and the risk of infection of non-vaccinated subjects, including HCW, has been minimal. As vaccination coverages increase and the incidence of measles declines, nosocomial transmission is likely to become an increasingly important source of measles virus in the population [19
]. In these circumstances, physicians are less familiar with diagnosing measles, and delays occur in the diagnosis and laboratory confirmation of measles [24
], increasing the risk of nosocomial transmission. HCW have been affected by many outbreaks and their role in measles transmission is key on many occasions [15
]. Given the potential severity of measles and the ease of transmission in healthcare centres, vaccination of susceptible HCW is essential to control nosocomial infection and achieve progress in the elimination strategy [4
Because HCW are at extremely high risk of acquiring measles from patients or transmitting measles to patients and co-workers in medical settings, in addition to the universal vaccination of children, the vaccination of susceptible individuals working in healthcare facilities with two doses of vaccine separated by an interval of at least 28 days is currently recommended [5
Most HCW are immune to measles, but many cannot provide sufficient accessible evidence of documented immunity. If outbreaks occur, these HCW should be temporarily taken off health care work, which may cause severe logistic and financial problems [24
]. In circumstances in which HCW state they know their history [30
], undocumented information is clearly not sufficient to justify overriding these problems. This is true even for situations in which the PPV for immunity of having had measles or being vaccinated are high, as in the present study.
In the era of measles elimination, the goal is 100% immunity in populations at high risk of acquiring measles, such as HCW. The risk of acquiring measles is estimated to be 13 to 19 times higher for susceptible HCW than for the general population [4
]. The criteria accepted as sufficient evidence of immunity in the general population may be insufficient in HCW, especially in younger age groups. These criteria should be reviewed, replacing the required documentation of physician-diagnosed disease as a evidence of measles immunity by laboratory confirmation of measles [13
]. Those HCW who cannot provide proof of laboratory-confirmed measles or receipt of 2 doses of MCV should receive a full course of vaccination [4
In Catalonia, the priority should be the availability of information on HCW measles immunity. Measles serology should be required in all HCW born after 1966 without documented evidence of vaccination with two doses of MCV or laboratory confirmation of the disease. The data should be stored and easily accessible, in computerized occupational records [4
]. The vaccination card demonstrated limited usefulness in confirming vaccination in our study, suggesting that the undocumented histories reported by HCW have little validity. Another preoccupation is the possible limitation of the vaccination history of two doses as a criterion to ensure immunity. Although this information was only obtained in 50 HCW, serologies were negative in 4%. In addition, in the 2010 outbreak in Catalonia, one of the 11 HCW affected was an emergency room physician who had 2 documented doses of MCV [10
A lesser priority should be routine review of the situation of unvaccinated HCW born before 1966 who lack laboratory evidence of measles immunity or laboratory confirmation of measles, in whom the recommendation of two doses of MCV should be strongly considered.
One limitation of this study is that, as we used a convenience sample, the results may not be generalizable to all HCW in Catalonia. Likewise, the serological study was made in HCW who voluntarily attended ORP health examinations: therefore, the prevalence of measles immunity in the study subjects may differ from that of HCW who did not attend these health examinations. However, the large sample size, which included hospital and primary healthcare centre workers from 5 of the 7 Catalan health regions, added to the fact that less than 5% of HCW invited to participate refused, suggest that our results may reflect the true situation in many Catalan health centres.