Question
DPT vaccine
Answer
DPT vaccine is a combination vaccine protecting against Diphtheria, Pertussis (whooping cough), and Tetanus — three important childhood diseases — and is a cornerstone of routine national immunization schedules worldwide.
Components: diphtheria toxoid and tetanus toxoid (both formalin-inactivated exotoxins, which retain immunogenicity but not toxicity), combined with a pertussis component, which may be either whole-cell (wP) — killed whole Bordetella pertussis organisms, more reactogenic but generally providing robust/longer-lasting immunity — or acellular (aP) — purified specific pertussis antigens (e.g., pertussis toxoid, filamentous haemagglutinin, pertactin), with a more favourable side-effect profile.
Schedule: a primary series of 3 doses in infancy (commonly at 6, 10, and 14 weeks, though schedules vary by national programme), followed by booster doses (typically at 18 months and around 5 years of age); a Tdap booster during pregnancy is additionally recommended in many programmes to protect the neonate via passive transfer of maternal pertussis antibody.
Mechanism: stimulates active immunity — antitoxin antibody against diphtheria and tetanus toxins (protecting against the toxin-mediated disease manifestations, even if the organism itself is not eliminated), and antibody/cellular immunity against pertussis antigens.
Adverse effects: local reactions (pain, swelling at injection site) are common, especially with whole-cell pertussis vaccine; rare but serious reactions (e.g., encephalopathy) historically prompted the development of the safer acellular pertussis alternative.