[Randomized clinical trial on the effectiveness of a postal reminder to increase tetanus-diphtheria vaccination coverage in the young adult population]. / Ensayo clínico aleatorizado acerca de la efectividad del recordatorio postal para aumentar la cobertura vacunal contra tétanos-difteria en población adulta joven.

OBJECTIVE: To evaluate the effectiveness of individual postal reminders compared with no action of any kind in increasing the tetanus-diphtheria immunization rate in the population aged between 24 and 30 years old in an area where a general population strategy was simultaneously being conducted through information posters on tetanus vaccination. METHOD: We performed an open, randomized clinical trial with parallel groups among the population aged 24-30 years old in a basic health area with 13,523 inhabitants over a 3-month period in 2005. There were 311 patients in the control group and 311 in the experimental group, after exclusion of individuals correctly vaccinated according to the computerized medical records system. The intervention evaluated was a postal reminder on tetanus vaccination. The response variable was the immunization rate due to the intervention. Other variables studied were sex, age, reason for seeking vaccination, compliance with the vaccination timetable, whether vaccination was rejected, and whether prior vaccination was verified. The statistical analysis consisted of Student's t-test and the chi2 test, with a confidence level of 95% (p < 0.05). RESULTS: Vaccination coverage among the general population at the end of 2005 was 75.6%. After the postal reminder, 22.2% of the control group and 40.5% of the experimental group were correctly vaccinated. CONCLUSIONS: Individual postal reminders sent to the population aged between 24 and 30 years is effective in increasing the immunization rate in this age group. Periodic reminders could help to ensure continuity in vaccination of the adult population.