RESUMEN
BACKGROUND: Tetanus-diphtheria toxoids (Td) booster immunization is generally recommended for Grade 9 students (14- to 16-year-olds) but targeting younger students may enhance vaccine uptake or facilitate simultaneous vaccinations. However, earlier vaccination might cause greater side effects. This study was undertaken to compare the safety of Td vaccinations in students in Grade 6 (11 to 12 years old) and Grade 9. METHODS: A controlled, sequential assessment of Td vaccine, adsorbed, was conducted in one urban school district, starting with Grade 9 students. Grade 6 students were given Td concurrently with Dose 3 of hepatitis B vaccine. Adverse effects were assessed during visits 2 days after vaccination. Participation criteria, immunization technique and assessment procedures were standardized. RESULTS: Of 410 students vaccinated, 204 in Grade 9 and 206 in Grade 6, 391 (95.4%) were assessed in person. Nineteen missed follow-up visits but telephone interviewers established that none missed school because of vaccine side effects. At follow-up Grade 6 students more often reported deltoid pain with arm movement (35.2% vs. 10.8%, P < 0.001). Injection site redness > or = 50 mm in diameter was present in 12.2% of Grade 6 and 3.6% of Grade 9 students (P < 0.001) whereas swelling > or = 50 mm diameter was present in 22.4 and 10.8%, respectively (P < 0.01). Fewer than 10% of subjects took analgesics for injection site pain. Only 5 students (1.3%) rated Td site morbidity as severe/unacceptable. Hepatitis B site morbidity was minimal in comparison. CONCLUSION: Td boosters were moderately reactogenic in adolescents. Younger students more often experienced injection site morbidity but considered it bearable. Booster immunizations can reasonably be offered within the age range of 11 to 16 years.