Families can heighten individuals’ risks of contracting measles. Measles clusters within families given the intimacy of family life; an infected person’s family member has a significantly greater risk of infection than random individuals. Family behaviors also create unequal health risks, as demonstrated with the Disneyland outbreak. Millions of families with young children flock to Disneyland every year. Even if only 2% of these families have not vaccinated their children, this translates into thousands of susceptible children coming in contact with each other. Together, families’ vaccination decisions and vacation plans created heightened risks for some children, but not others.