All children < 6 months old seen at the hospital who did not have measles were given measles immune globulin. If these children were subsequently vaccinated, the immune globulin could impair vaccine effectiveness for up to 9 months.
Measles immune globulin, which provides short term temporary protection, is usually reserved for a child with immune deficiency problems or a baby during their first few weeks of life if his/her mother doesn't have immunity.