EPI primary vaccination alone cannot control the disease. Additional specific immunization activities are essential.
Control is the first step in any vaccination programme. Its aim is to reduce disease morbidity and mortality (the number of cases and the number of deaths).
In particular, control is the objective of mass vaccination campaigns conducted during population influxes (IDPs/refugees) or in response to an outbreak.
Control strategies have four components:
- improving patient management;
- increasing routine vaccination in order to attain primary measles vaccination coverage ≥ 90% in children under 1 year;
- administering a second dose of vaccine during supplementary immunization activities (SIAs): an initial catch-up campaign to eliminate measles susceptibility in the population (objective: ≥ 95% coverage in children ages 6 months to 15 years), then follow-up campaigns to vaccinate all children born since the last SIA (objective: ≥ 95% coverage in children ages 6 to 59 months). The interval between these campaigns should be adjusted according to the epidemiological situation (from 2 to 4 years);
- increasing surveillance and assessing the impact of activities in order to fine-tune the strategies.
Rapid outbreak response vaccination was added to the control strategy arsenal in late 2011.
Elimination strategies aim at stopping circulation of the virus in a large geographic area. While there are no more cases, the risk of reintroduction of the virus makes maintaining very high immunization coverage crucial.
Elimination relies on four activities:
- improving treatment of cases, including routine administration of vitamin A;
- setting up surveillance for each suspected case: investigation and laboratory confirmation;
- maintaining a routine primary measles vaccination coverage ≥ 95% in children less than 1 year;
- offering a second chance for vaccination (SIA) to keep the cohort of susceptibles below the critical threshold.
Countries who resort to regular SIAs to achieve a high level of immunity in the population should not consider ending these SIAs before routine administration of two vaccine doses reaches a coverage of at least 90 to 95% nationally.
Eradication means a complete end to transmission of the wild virus in the world. There are no more cases or transmission, and immunization activities can be stopped. This final phase cannot be implemented until the virus has been successfully eliminated worldwide.