Herd immunity occurs when a high enough percentage of the population becomes immune that a virus cannot be easily transmitted from person-to-person. Immunity is typically achieved through having the disease or through vaccinations. With regard to COVID-19, it has been estimated that to achieve herd immunity 60-80% of the population may need to be immune. Since there currently is no vaccine, the only way to achieve immunity now is to be infected; however, it is not known how long this natural immunity lasts. Additionally, long-lasting effects of COVID-19 have been reported, which would be a problem with achieving immunity via being infected. Learn more in our epi mini-lesson.