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Immunity and immunization of children against diphtheria in Sweden
A Mark1, B Christenson, M Granström
1Division of Child Health, Landstingets kansli, Jönköping, Sweden.
Insights
Diphtheria immunity wanes over time, with many children lacking protective antitoxin levels. Booster vaccinations significantly increase immunity, highlighting the need for serologic monitoring in vaccination programs.
Area of Science:
- Immunology
- Vaccinology
- Public Health
Background:
- Childhood vaccination schedules aim to establish long-term immunity.
- Immunity to diphtheria can decrease over time, potentially leaving individuals susceptible.
- Understanding diphtheria antitoxin levels is crucial for assessing vaccine effectiveness.
Purpose of the Study:
- To investigate diphtheria immunity levels in children of different ages.
- To evaluate the impact of varying diphtheria toxoid vaccine doses on immunity.
- To determine the necessity of serologic monitoring for vaccination programs.
Main Methods:
- Assessed diphtheria antitoxin levels in 457 children aged 6, 10, and 16 years.
- Administered booster doses of diphtheria-tetanus vaccine at different volumes.
- Monitored antitoxin levels and adverse reactions post-vaccination.
- Examined a cohort of 5-year-olds vaccinated with extended primary intervals.
Main Results:
- Prior to booster, significant percentages of children (15-48%) had suboptimal diphtheria antitoxin levels.
- Booster vaccinations with diphtheria-tetanus vaccine rapidly increased antitoxin levels in over 97% of children.
- Different booster doses resulted in 23-96% achieving long-term protective antitoxin levels (≥1 IU/ml).
- Extended primary vaccination intervals showed high efficacy, with only 1.4% below protective levels.
Conclusions:
- Childhood diphtheria immunity diminishes, necessitating booster doses.
- Booster vaccinations are effective in restoring protective antitoxin levels.
- Serologic monitoring of vaccination programs is recommended to ensure sustained population immunity.
Abstract:
The level of immunity to diphtheria and the effect of vaccination with different doses of diphtheria toxoid was investigated. The 457 study children, 6, 10 and 16 years of age, had as infants received routine primary vaccination with three doses of diphtheria-tetanus-toxoid or diphtheria-tetanus-pertussis vaccine, and the 16 year-olds also had received a booster dose of tetanus with a small dose of diphtheria at the age of ten. Prior to the study booster, 15% of the 6-year-olds had antitoxin levels against diphtheria less than 0.01 IU/ml, the given minimum level for protection. Of the 10-year-olds, 48% had titres less than 0.01 IU/ml, while the corresponding figure for the 16-year-olds was 24%. After a booster injection of 0.1, 0.25 or 0.5 ml of diphtheria-tetanus vaccine, more than 97% of the children showed titre levels greater than or equal to 0.1 IU/ml, while levels of greater than or equal to 1 IU/ml, indicating titres sufficient for long-term protection, were attained by 23-96%. Systemic reactions were few and moderate. Local reactions were of little clinical significance. In a group of 5-years-olds given diphtheria-tetanus primary vaccinations over wider intervals, only 1.4% had antitoxin titres less than 0.01 IU/ml. The results show a need for serologic monitoring of vaccination programmes.