CNN: The ‘chicken and egg’ reason why polio outbreaks still happen
“If polio is near extinction, why do outbreaks still pop up in places where the disease was thought to be long gone? The answer is complicated. … [S]ome immunization efforts carry the very rare risk of causing polioviruses to circulate in areas where many people might not yet be vaccinated or areas that were poorly vaccinated — an event that could lead to new cases of disease while trying to demolish it…” (Howard, 7/10).