Epidemiology of two large measles virus outbreaks in Catalonia

Abstract

Measles cases in the European Region have been increasing in the last decade; this illustrates the challenge of what we are now encountering in the form of pediatric preventable diseases. In Catalonia, autochthonous measles was declared eliminated in the year 2000 as the result of high measles-mumps-rubella vaccine (MMR) coverage for first and second dose (15 mo and 4 y) since the mid-1990s. From then on, sporadic imported cases and small outbreaks appeared, until in 2006-2007 a large measles outbreak affecting mostly unvaccinated toddlers hit the Barcelona Health Region. Consequently, in January 2008, first dose administration of MMR was lowered from 15 to 12 mo of age. A new honeymoon period went by until the end of 2010, when several importations of cases triggered new sustained transmission of different wild measles virus genotypes, but this time striking young adults. The aim of this study is to show the effect of a change in MMR vaccination schedule policy, and the difference in age incidence and hospitalization rates of affected individuals between both outbreaks. Epidemiologic data were obtained by case interviews and review of medical records. Samples for virological confirmation and genotyping of cases were collected as established in the Measles Elimination plan guidelines. Incidence rate (IR), rate ratio (RR) and their 95% CI and hospitalization rate (HR) by age group were determined. Statistic z was used for comparing proportions. Total number of confirmed cases was 305 in the 2010 outbreak and 381 in the 2006-2007 outbreak; mean age 20 y (SD 14.8 y; 3 mo to 51 y) vs. 15 mo (SD 13.1 y; 1 mo to 50 y). Highest proportion of cases was set in ≥ 25 y (47%) vs. 24.2% in 2006 (p < 0.001). Differences in IR for ≤ 15 mo (49/100,000 vs. 278.2/100,000; RR: 3,9; 95%CI 2,9-5.4) and in overall HR 29.8% vs. 15.7% were all statistically significant (p < 0.001). The change of the month of age for the administration of the first MMR dose proved successful to protect infants. Yet, given the current epidemiological situation, continued awareness and efforts to reach young adult population, especially those at high risk of infection and transmission such as healthcare workers and travelers, are needed to stop the spread of the virus when importations occur.

Prevalence of measles antibodies among health care workers in Catalonia (Spain) in the elimination era

“…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]. …”

“…Between November 2010 and September 2011, there was another outbreak with transmission among the native population that affected 305 people, mostly unvaccinated adults aged > 25 years, including 11 HCW, of whom one had received two doses of MCV [10]. Currently there is no continuous transmission of measles in Catalonia.…”

Implication of health care personnel in measles transmission

“…After this event, there have been other significantly important outbreaks. 14,15 The aim of this study was to assess the implication of HCP in measles transmission related to healthcare setting in the years following autochthonous measles elimination in Catalonia.…”

Measles outbreak in Dubrovnik-Neretva County, Croatia, May to June 2018

“…There was one case of measles-associated pneumonia. The typical hospitalisation rate for measles cases is one in four [14], and hospitalisation rates for other outbreaks in Europe ranged from 15.7% to 47% [15][16][17][18]. The high hospitalisation rate in this outbreak (11/15 cases) might reflect the need for isolation, rather than severe illness.…”