Toddlers: measles, mumps, rubella, polio, tetanus, diphtheria, pertussis, flu, hepatitis, chickenpox.

Infants: Infants are particularly at risk for pertussis (whooping cough) because they aren't fully immunized until six months.

Adolescents: A pertussis booster is now recommended for children at ages 11 and 12. Federal data show that 52 percent of Minnesota adolescents received the booster in 2009, slightly below the national average.