Pertussis Immunization Data
Here in the Pacific Northwest, immunization rates for pertussis in 2010 were similar to the national average of 84.4 % of two year olds who had all 4 doses of DTaP (See Table 1) according to the 2010 CDC National Immunization Survey.
The most recent reporting from IHS and Tribal sites shows that in the Portland Area IHS overall, 70.4% of AI/AN two-year olds are up to date with all four doses of DTaP, ranging from 60.0% in OR to 78.2% in ID. Nationally, IHS and Tribal sites report 81.7% of AI/AN two year olds are fully immunized against pertussis. These levels of vaccine coverage are insufficient to keep communities protected from disease outbreaks. Furthermore, within each state, there are communities where immunization coverage is much lower than the average, which creates conditions for an outbreak of pertussis to occur and spread.
Table 2, below, shows DTAP coverage for specific age groups in the Portland Area. Rates of appropriately immunized infants are below 80% in all age groups and in all three states. Rates tend to decrease after 3 to 4 months of age with some catch up by 24 to 27 months. However, this leaves infants in adequately immunized for most of their first two years of life.
Data in Table 3, below, shows the percent of children who are up to date with all recommended immunizations, by age group. A pattern similar to that seen for DTAP alone (Table 2) is also seen. In many instances, adequate DTAP vaccination is the limiting factor in children being appropriately immunized at any age group.
The diphtheria-tetanus-acellular pertussis vaccine (DTaP) is routinely given starting at 6 weeks of age to prevent pertussis, but full immunity for children requires at least four vaccines before the age of two and an additional dose given at age 4 or 5 years. Immunity begins to wane in the middle school years so a booster (known as TDaP) should be given to adolescents and adults starting at age 11. Many cases are believed to be linked to adolescents or young adults who have not been fully vaccinated and become ill with mild symptoms that last for several weeks. The long duration of illness and close contact to infants means they are able to pass the infection on to those who are more likely to become severely ill.