100M Catch-Up Doses Across 36 Nations Stress-Test Cold Chain Limits

Gavi, WHO, and UNICEF have confirmed that the Big Catch-Up (BCU) initiative delivered more than 100 million vaccine doses to an estimated 18.3 million children across 36 countries between 2023 and March 2026. For vaccine manufacturers and supply chain directors, the scale of this multi-year surge operation exposes both the ceiling of existing cold chain infrastructure and the forecasting complexity that accompanies demand driven by accumulated immunity deficits rather than routine birth cohorts.

Of the children reached, an estimated 12.3 million were zero-dose, having never received any vaccine prior to BCU enrollment. A further 15 million had never received a measles vaccine. The programme also administered 23 million doses of inactivated polio vaccine (IPV) to un- and under-vaccinated children. The 36 participating countries, concentrated across Africa and Asia, collectively account for 60% of all zero-dose children worldwide, a concentration that defines where fill-finish capacity, last-mile cold chain, and health worker training investments must be sustained beyond the initiative's formal close.

Systemic infrastructure changes with procurement implications: BCU did not operate as a standalone campaign. Participating countries updated age-eligibility policies, trained health workers to identify and vaccinate missed children within routine care pathways, and established monitoring systems for older cohorts aged 1 to 5. Twelve countries, including Ethiopia, Pakistan, Somalia, and Kenya, reported reaching more than 60% of zero-dose children under age 5 who had previously missed DTP1. Ethiopia alone administered DTP1 to more than 2.5 million previously zero-dose children. These systemic changes alter the demand profile manufacturers and procurement agencies will need to model going forward.

Agencies caution that catch-up vaccination, while effective at closing acute immunity gaps, is not a substitute for robust routine immunization. Millions of infants continue to miss scheduled vaccines annually, particularly in fragile, conflict-affected, and underserved communities. Final BCU coverage data is still being compiled, though the initiative is forecast to meet its target of reaching at least 21 million un- and under-immunized children. For QA and regulatory teams supporting manufacturers supplying these markets, the BCU's infrastructure investments represent a baseline, not a ceiling, for what sustained demand planning must accommodate.