COVID-19 for the entire population is needed to achieve herd immunity and that vaccines will need to be given to young children.Currently, children under the age of 12 years old are ineligible to get a shot, which makes getting to such a high percentage difficult or impossible to obtain, the report indicates.The report, released on Monday, said the Delta variant is more transmissible, causes more severe disease and reduces the effectiveness of a single vaccine dose compared with other strains.