what immunizations are combined?
<answer> The 4:3:1:3 combined series of immunizations are 4 or more doses of diphtheria, tetanus, and pertussis vaccine, 3 or more doses of polio vaccine, 1 or more doses of a measles-containing vaccine, and 3 or more doses of Haemophilus influenzae type b vaccine. <context> 1 The 4:3:1:3 combined series measures the number of children who have received 4 key immunizations: 4 or more doses of diphtheria, tetanus, and pertussis vaccine, 3 or more doses of polio vaccine, 1 or more doses of a measles-containing vaccine, and 3 or more doses of Haemophilus influenzae type b vaccine (Hib). 2009 data are affected by a shortage of Hib vaccine that occurred between December 2007 and September 2009.