1. Clinical Overview
A quadrivalent, combined, adsorbed, acellular vaccine for active immunization against diphtheria, tetanus, pertussis (whooping cough), and invasive diseases caused by Haemophilus influenzae type b (Hib). It is a sterile suspension for intramuscular injection, containing purified toxoids and a conjugate antigen adsorbed onto an aluminum adjuvant to enhance immunogenicity. It is a critical component of the National Immunization Schedule in India for primary and booster vaccination in infants and children.
| Onset | Duration | Bioavailability |
|---|---|---|
| Immunological response begins within 7-14 days post-vaccination, but protective antibody levels are typically achieved after the completion of the primary series (3 doses). | Protection varies by component. Following a complete primary series and recommended boosters: Diphtheria/Tetanus protection can last ~10 years, Pertussis protection wanes after 4-12 years, Hib protection is long-lasting after the primary infant series. | Not applicable (N/A) for parenteral vaccines. The immunological 'availability' is considered 100% upon intramuscular administration. |
2. Mechanism of Action
The vaccine induces active immunity by stimulating the production of specific antibodies and memory B and T cells against the antigens. Diphtheria and Tetanus Toxoids: Inactivated forms of the exotoxins (Corynebacterium diphtheriae and Clostridium tetani) that induce neutralizing antibodies. Pertussis Toxoid: Inactivated form of the pertussis toxin from Bordetella pertussis, a key virulence factor. Haemophilus influenzae type b Conjugate Vaccine: The Hib capsular polysaccharide (polyribosylribitol phosphate, PRP) is chemically conjugated to a carrier protein (often Tetanus Toxoid). This conjugation converts the T-cell-independent PRP antigen into a T-cell-dependent antigen, eliciting a stronger, more durable immune response with robust memory, especially in infants.
3. Indications & Uses
- Primary immunization of infants and children from 6 weeks up to 5 years of age against Diphtheria, Tetanus, Pertussis, and invasive diseases caused by Haemophilus influenzae type b (e.g., meningitis, pneumonia, epiglottitis, septic arthritis).
- Booster vaccination in children as per the National Immunization Schedule (e.g., 16-24 months booster).
4. Dosage & Administration
Adult Dosage: Not indicated for adults. Adults require Td or Tdap formulations with reduced diphtheria and pertussis antigen content.
Administration: For intramuscular use only. Shake the vial or pre-filled syringe well before use. The preferred site for infants and young children is the anterolateral aspect of the thigh. In older children, the deltoid muscle can be used. Do not administer intravenously, intradermally, or subcutaneously. Use a separate, sterile syringe and needle for each individual. Do not mix with other vaccines in the same syringe unless specifically licensed for co-administration.
5. Side Effects
Common side effects may include:
- Pain, redness, and swelling at the injection site (≥1 in 10)
- Fever (usually mild to moderate, <39°C)
- Irritability, fussiness, drowsiness
- Loss of appetite
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Immunosuppressants (e.g., high-dose corticosteroids, chemotherapy, biologics like TNF-alpha inhibitors) | May diminish the immunological response to the vaccine, potentially leading to suboptimal protection. | Major |
| Other Vaccines (e.g., Rotavirus, Pneumococcal Conjugate, IPV) | Can generally be administered concomitantly at different injection sites. No clinically significant interference in immune response. Co-administration is standard practice in the UIP. | Minor |
| Anticoagulants (e.g., Warfarin) | Increased risk of bleeding or hematoma at the injection site. Administer with caution using a fine-gauge needle and apply firm pressure. | Moderate |
7. Patient Counselling
- DO complete the full schedule of 3 primary doses and the booster for optimal protection.
- DO inform the doctor/nurse of any history of severe reaction to a previous vaccine or any known allergies.
- DO keep a record of the vaccination (Mother & Child Protection card).
- DONT give aspirin or other salicylates for fever relief in children due to the risk of Reye's syndrome. Use paracetamol (acetaminophen) as advised.
- DONT massage the injection site vigorously.
8. Toxicology & Storage
Overdose: Accidental overdose is unlikely due to unit-dose packaging. Theoretical risks include a pronounced local reaction (severe pain, swelling) and heightened systemic symptoms (high fever, pronounced irritability).
Storage: Store at +2°C to +8°C (in a refrigerator). Do not freeze. Protect from light. Do not use if the vaccine has been frozen or exposed to temperatures outside the recommended range. The vaccine is sensitive to heat and freezing. Use immediately after opening the vial. Transport in a cold chain. Discard unused vaccine.