Why did routine smallpox vaccination end after global eradication?

Routine smallpox vaccination was discontinued following the global eradication of the disease in 1980 because the disappearance of the threat reduced the incentive for widespread prevention.12

The eradication campaign, led by the World Health Organization, successfully interrupted chains of transmission by using ring vaccination to isolate cases and vaccinate their contacts. Because smallpox has no nonhuman reservoir and infected individuals are generally only contagious after symptoms appear, public health officials were able to effectively eliminate the virus from the human population.23

Once the disease was declared eradicated, the risks associated with the vaccine—which contains live vaccinia virus and can cause side effects ranging from fever to severe complications like myocarditis or pericarditis—outweighed the benefits of continuing routine immunization for the general public. Today, vaccination is reserved only for specific groups at increased risk of exposure, such as certain laboratory or military personnel, while many countries maintain strategic stockpiles to prepare for potential emergencies.2