Texas Retrospective Immunization Survey (TRIS) - Vaccination Coverage Levels

1999 Texas Retrospective Immunization Survey (TRIS)

The TRIS is a school-based study conducted by the Texas Department of Health. The TRIS measures immunization coverage rates of kindergarteners retrospectively at two years of age. For example, the majority of the immunization records reviewed for the 1999 TRIS were for children born in 1992-1993. Children were considered up-to-date on their immunizations if they had completed the 4-3-1 series (4 doses of diphtheria-tetanus-pertussis vaccine, 3 doses of polio vaccine, 1 dose of measles-mumps-rubella vaccine) by the time they turned two years of age in 1994-1995.

Results showed the statewide 4-3-1 immunization rate at 24 months of age at 63.7%. The TRIS 4-3-1-3 immunization rate (4-3-1 plus 3 doses of Haemophilus influenzae type b vaccine) for the same age group was 58.7%.

Thus, 1999 TRIS data reflect the immunization coverage levels of the 1998-1999 kindergarten population when they were 24 months of age (about three years prior to the survey date) rather than the levels of the 1998-1999 24-month old population.

View the Texas Immunization Rates by Public Health Region (1999 TRIS).

Retrospective Assessment of Preschool Vaccination Status in Galveston County, Texas, 1999

Epidemiology Department
Galveston County Health District, December 1999


Vaccination coverage of Galveston County preschool children was assessed through a retrospective survey of immunization records for students enrolled in kindergarten during the fall of 1999. These children became 2 years of age in 1995-96. Eight hundred and sixty one records in 29 schools were reviewed.

Survey results indicate that 56.2% of the children were adequately vaccinated with DTP4, Polio3, and MMR1 (4-3-1 series) by age 2.

Estimated percent of vaccination coverage with the 4-3-1 series 1 among 24 month olds according to the Retrospective Immunization Surveys conducted by local health authorities
County/City Coverage
Galveston County 56.2%

1 Completion of 4 doses of diphtheria-tetanus-pertussis vaccine, 3 doses of polio vaccine, 1 dose of measles-containing vaccine.

Compared to 1998 survey results, at age 2, there was a small decrease in the proportion appropriately vaccinated (from 57.7 to 56.2%). There was also a decline (4.2%) in vaccination coverage at age 5; 85.2% were adequately vaccinated with DTP4, Polio3, and MMR1 compared to 89.4% for students enrolled in kindergarten during the fall of 1998. At ages 3 months, 7 months, and 1 year, there were statistically significant increases in vaccination coverage.

Ninety-five percent confidence intervals were calculated for each estimated vaccination coverage level mentioned above. The increases were significantly different from the 1998 survey, but the decreases were not. Each of the last six annual surveys has shown improvement in the proportions of children adequately vaccinated by ages 2 and 5. The 1999 survey results reflect improvement of about 15% for 2 year olds and 7.5% for 5 year olds compared to 1993.

Substantial declines were observed again from the proportion adequately vaccinated at age 3 months (80.3%) to that at age 7 months (51.5%), and from age 12 months (77.2%) to age 19 months (45.9%). This is evidence of the need for an effective vaccination tracking system that can generate reminders to parents and providers.

Since the percentages of children at various ages who received specific single vaccine doses were somewhat higher than the percentages of children who had received the complete recommended series of vaccines, it appears that medical providers do not always provide all age-appropriate vaccines simultaneously.

The results of this survey can be used to select target areas for special vaccination efforts. The localities served by the nine schools in which students had the lowest vaccination levels at age 2 are recommended as target areas. These include Galveston (east,west and central), Dickinson, High Island, and Bacliff.

For a copy of the comprehensive report on the Galveston County retrospective survey, contact Chuck Chambers, Galveston County Public Health District, at (409) 765-2514.

Last updated September 30, 2016