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Long term serologic follow-up after pertussis immunization
1Department of Pediatrics, Karolinska Institute, Sachs' Children's Hospital, Stockholm, Sweden.
Insights
Antibody levels to pertussis toxin decrease rapidly after booster shots in young children. However, most children maintained protective antibody levels, suggesting current vaccines offer good protection against whooping cough.
Area of Science:
- Immunology
- Vaccinology
- Pediatrics
Background:
- Pertussis toxin (PT) is a key virulence factor in *Bordetella pertussis*.
- Neutralizing antibodies to PT (antitoxin) are a correlate of protection against pertussis.
- Assessing long-term antibody persistence after vaccination is crucial for understanding vaccine efficacy and duration of protection.
Purpose of the Study:
- To determine the persistence of neutralizing antibodies to pertussis toxin (antitoxin) in 4-year-old children.
- To compare antitoxin levels after primary immunization with acellular versus whole-cell pertussis vaccines, followed by an acellular booster.
- To evaluate the protective efficacy of vaccine-induced antitoxin levels against pertussis infection.
Main Methods:
- Blood samples from 201 children aged 4 years were analyzed for antitoxin levels.
- Children had received primary immunization at 6-8 months with acellular (n=149) or whole-cell (n=52) pertussis vaccine.
- A booster dose of acellular vaccine was administered to 195 children 9-16 months prior to sample collection. Data on pertussis exposure and disease occurrence were also collected.
Main Results:
- A rapid and significant decrease in antitoxin levels was observed between immediate post-booster titers and levels measured 24 months later.
- The rate of antitoxin decrease per month was significantly greater after the booster than after the primary immunization series (P < 0.001).
- Despite the decline, 86% of children maintained measurable antitoxin levels, and none of the 19 exposed children developed whooping cough.
Conclusions:
- Long-term follow-up is essential for evaluating new vaccines and immunization schedules.
- Current acellular pertussis vaccine boosters appear to provide sufficient antibody concentrations for protection against whooping cough for at least 24 months post-booster.
- Further research is needed to determine optimal booster intervals to maintain protective immunity throughout childhood.
Abstract:
Neutralizing antibodies to pertussis toxin (antitoxin) were determined in 201 blood samples from 4-year-old children. They had received primary immunization at 6 to 8 months of age with an acellular (n = 149) or a whole cell (n = 52) pertussis vaccine and 195 of them had received a booster dose of the acellular vaccine 9 to 16 months later. Data on exposure to pertussis and occurrence of pertussis were also collected. There was a rapid decrease of antitoxin between immediate postbooster titers and those measured 24 months later. This decrease per month was significantly greater than that after the primary immunization series (P less than 0.001). Neither the number nor the spacing of acellular vaccine doses given for primary series influenced the titers found 24 months after the booster. An antitoxin response was still measurable in 86% of the 196 four-year-old children. None of 19 exposed children developed whooping cough, which suggested that the antibody concentrations during the follow-up period were sufficient for protection. The results indicate a need for long term follow-up studies in the evaluation of new vaccines and immunization schedules.