Measles-Related Hospitalizations in Italy, 2004-2016: The Importance of High Vaccination Coverage

Measles is a highly contagious human infectious disease. It can lead to serious complications and often requires hospitalization. In Italy, as in other European countries, the goal of measles elimination in 2015 failed. To reach this target, identifying susceptible individuals, closing any immunity gaps and reaching adequate vaccination coverage is necessary.

To contribute to these purposes, a retrospective observational study on measles-related hospitalization between 2004 and 2016 in Italy was conducted, using the national hospital discharge database as informational flow.

Admission frequencies and hospitalization rates were compared between regions with low (<90%) and high (≥90%) vaccination coverage for measles at age 24 months. Categorical variables were analyzed using the χ2 test or the χ2 test for trend for ordinal variables; t test was performed to verify the significance when annual average hospitalization rates were compared. Trends of vaccination coverage and hospitalization rates were analyzed using the slope of the regression line.

During the study period, 9,546 measles-related hospitalizations were collected in Italy, with an average annual number equal to 734. The overall measles hospitalization rates increased from 0.21 × 100,000 persons in 2004 to 0.82 × 100,000 in 2016 (β = 0.04; p = 0.689). A shift of mean age (from 1-17 years to 18-44 years) of measles-related hospitalizations was shown. A number of admissions for the low vaccination coverage group about twice as much as recorded for the other regional group was shown (6,344 vs 3,202). The involvement of 18-44 age class in the high vaccination coverage group was 14% higher compared with the low vaccination coverage group, in which, however, the 1-17 age class presented a 16% higher frequency.

These findings confirmed that large measles epidemics continue to occur in Italy, although with regional differences related to different rates of measles immunization. Vaccination coverage >90% led to a halving of measles hospitalizations, but it is insufficient for the elimination: ≥95% coverage continues to be the target to be reached.