Children younger than 5, but especially children younger than 2 years old
Adults 65 years of age and older
Pregnant women
People who have medical conditions including:
-Asthma
-Neurological and neurodevelopmental conditions [including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy (seizure disorders), stroke, intellectual disability (mental retardation), moderate to severe developmental delay, muscular dystrophy, or spinal cord injury].
-Chronic lung disease (such as chronic obstructive pulmonary disease [COPD] and cystic fibrosis)
-Heart disease (such as congenital heart disease, congestive heart failure and coronary artery disease)
-Blood disorders (such as sickle cell disease)
-Endocrine disorders (such as diabetes mellitus)
-Kidney disorders
-Liver disorders
-Weakened immune system due to disease or medication (such as people with HIV or AIDS, or cancer, or those on chronic steroids)
People younger than 19 years of age who are receiving long-term aspirin therapy
People who are morbidly obese (Body Mass Index, or BMI, of 40 or greater)