Nigeria is battling a diphtheria outbreak that has reached 18,000 suspected cases and 630 deaths, a case fatality rate of 3.5%. PandemicAlarm rates this event at 3/5 severity. What makes this outbreak particularly stark is that diphtheria is preventable with a routine childhood vaccine that has existed since the 1920s.
Why is this happening?
DPT3 vaccination coverage, the standard three-dose diphtheria-pertussis-tetanus series given in infancy, has dropped below 50% in several northern Nigerian states. Kano, Bauchi, and Yobe have been hit hardest. In some local government areas, coverage falls below 30%.
Multiple factors drive the gap. Insecurity from Boko Haram and bandit activity has disrupted health services across the northeast and northwest for over a decade. Cold chain infrastructure for vaccine storage is unreliable in remote areas. Vaccine hesitancy, fueled partly by a legacy of distrust dating back to the 2003 polio vaccine boycott in northern states, continues to suppress uptake even where supplies are available.
When enough children in a community go unvaccinated, Corynebacterium diphtheriae (the bacterium that causes diphtheria) finds a susceptible population and spreads. Most cases in this outbreak are children under 15 who never received their primary vaccination series.
What does the response look like?
Nigeria's National Primary Health Care Development Agency launched emergency vaccination campaigns in affected states starting in late 2024. WHO and UNICEF are supporting with vaccine supply, surveillance strengthening, and case management. Diphtheria antitoxin, which neutralizes the toxin produced by the bacteria, is the primary treatment alongside antibiotics. Global antitoxin supplies are limited, and procurement has been a challenge.
By early 2026, reactive vaccination campaigns had reached over 3 million children in the most affected local government areas. Coverage gaps remain significant, especially in hard-to-reach communities affected by conflict and displacement.
Why does this matter beyond Nigeria?
Diphtheria outbreaks are a signal of broader immunization failure. When routine vaccination programs break down, diseases that were controlled for decades return. Indonesia saw a diphtheria resurgence starting in 2017. Yemen and Venezuela experienced outbreaks amid political and economic collapse. Each case follows the same pattern: vaccine coverage drops, susceptible populations accumulate, and an old pathogen fills the gap.
Globally, WHO and UNICEF estimated that 14.3 million children received zero routine vaccine doses in 2023 — so-called "zero-dose" children. Each one represents a potential link in an outbreak chain for diphtheria, measles, pertussis, and other vaccine-preventable diseases.
Nigeria accounts for the largest share of zero-dose children in the world. Until routine immunization reaches the communities currently being missed, outbreaks like this one will recur. Emergency campaigns save lives in the short term, but they cannot substitute for a functioning routine immunization system.
Track this outbreak and others driven by vaccination gaps on the PandemicAlarm map. For more on how vaccine supply failures contribute to outbreaks, see our coverage of vaccine supply chain breakdowns.