Effectiveness of Digital Contact Tracing Policies in Controlling Infectious Disease Spread

Abstract: Disruptions in routine immunization programs can undermine population immunity and lead to outbreaks of vaccine-preventable diseases (VPDs). In addition to the direct threat posed by COVID-19, operational and logistical challenges, disruption of supply chains, and the effect of COVID-19 on the health system, health workforce, and disease surveillance can hinder vaccination and leave children unprotected against diseases such as measles, polio, and yellow fever. Monitoring vaccination coverage, adaptation of immunization activities, and strengthening sentinel surveillance can facilitate early detection of VPD outbreaks. Recovery in routine immunization programs requires not only the resumption of normal health service delivery but also catch-up campaigns, improvement in supply chains, and intensive engagement with affected communities.

Vaccination coverage is usually monitored on the basis of reported national administrative data but without formal validation, which compromises confidence in estimates of the actual number of children vaccinated, especially during wartime or severe epidemics. Coverage has fallen in many countries. Despite recommended herd immunity thresholds of at least 95%, suboptimal immunity may persist in areas with low vaccination coverage. Even in countries where high coverage is achieved at the national level, pockets of low uptake can facilitate the spread of VPDs.

Keywords: Routine immunization disruption, Vaccine coverage decline, Immunization service interruption, Vaccine- preventable disease resurgence, Herd immunity gaps, Public health system resilience, Health service disruptions, Pandemic impact on immunization, Childhood vaccination delays, Missed vaccination opportunities, Health inequities in immunization, Supply chain interruptions for vaccines, Vaccine stockouts, Community-level disease outbreaks, Maternal and child health outcomes, Surveillance gaps in immunization programs, Catch-up vaccination strategies, Immunization program recovery, Morbidity and mortality from preventable diseases, Global immunization coverage trends.