New preventive strategy to eliminate measles, mumps and rubella from Europe based on the serological assessment of herd immunity levels in the population.

Herd immunity blocks the transmission of measles, mumps and rubella in a population group when the prevalence of positive serologic results (p) is higher than a critical value (p c), known as the herd immunity threshold. A new preventive strategy should be developed in order to achieve the elimination of measles, rubella and mumps in Europe based on the serological assessment of herd immunity levels in different population groups. This strategy could detect population groups without herd immunity (p < p c) and indicate the additional vaccination coverage required in these groups in order to establish herd immunity and prevent outbreaks. The serological assessment of herd immunity levels in Catalonia, Spain, showed that herd immunity had not been established for measles and mumps in schoolchildren (5-9 years of age) and youths/younger adults (15-29 years of age), and that the additional vaccination coverage required to establish herd immunity in these groups was 1-7%. The new preventive strategy should be used to detect priority population groups for preventive and surveillance activities in European countries.