Hexavalent Infant Vaccine

The hexavalent (6-in-1) infant vaccine is a fully liquid combination vaccine that provides active immunization against six serious childhood diseases in a single injection. It significantly reduces the number of injections needed during routine infant immunization while providing immunogenicity comparable to administration of the individual vaccine components.

Six Diseases Prevented

1. Diphtheria — caused by Corynebacterium diphtheriae; produces a thick throat coating that obstructs breathing and can cause heart failure, paralysis, and death.
2. Tetanus (lockjaw) — caused by Clostridium tetani (soil bacterium) entering through wounds; causes painful muscle spasms and can be fatal. Vaccination is the only protection.
3. Pertussis (whooping cough) — caused by Bordetella pertussis; severe coughing fits, particularly dangerous in infants, can cause pneumonia, brain damage, or death.
4. Poliomyelitis — caused by poliovirus; can cause permanent paralysis. Near-eradicated globally through vaccination but still endemic in some regions.
5. Hepatitis B — caused by hepatitis B virus; liver infection that can become chronic, leading to cirrhosis and liver cancer. Highly contagious through blood and bodily fluids; infants are at high risk of chronic infection.
6. Haemophilus influenzae type b (Hib) — bacterial pathogen that causes invasive disease (meningitis, pneumonia, epiglottitis, sepsis). Before the vaccine, Hib was a leading cause of bacterial meningitis in young children.

Vaccine Components

• Diphtheria toxoid: ≥30 IU per dose.
• Tetanus toxoid: ≥40 IU per dose.
• Acellular pertussis antigens: pertussis toxoid 25 µg, filamentous hemagglutinin 25 µg, pertactin 8 µg (and fimbriae types 2/3 in some formulations).
• Inactivated poliovirus: types 1, 2, and 3.
• Recombinant hepatitis B surface antigen (HBsAg): 10 µg.
• Hib polysaccharide: 10 µg, conjugated to a carrier protein (typically tetanus toxoid).
• Aluminum salts as adjuvants.

Mechanism of Action

The vaccine contains inactivated/purified antigens (no live organisms) and stimulates B cells to produce specific antibodies and T cells to create cellular immunity and immune memory. After exposure to the actual pathogens, antibodies neutralize toxins and pathogens and memory cells enable a rapid response.

• Immunogenicity: >95% of infants develop protective antibody levels after the primary series for all six components, non-inferior to the individual vaccines.
• Diphtheria, tetanus, polio, hepatitis B, Hib: >95% protective antibody levels.
• Pertussis: 80–98% efficacy depending on the protocol; wanes over time, requiring boosters in adolescence and adulthood.
• Real-world impact: dramatic reductions in vaccine-preventable disease worldwide; near-elimination of diphtheria, polio, and invasive Hib disease in vaccinated populations.
• Safety: excellent safety record; combination vaccine is as safe as the individual vaccines, and fewer injections reduce distress and improve compliance.

For active immunization of babies and toddlers from six weeks of age against diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B, and invasive disease (such as meningitis) caused by Haemophilus influenzae type b, per the Hexyon EPAR.

Schedule (per Hexyon EPAR): the recommended initial vaccination schedule is either two doses given two months apart, or three doses given at least one month apart. A booster dose should be given at least six months after the last of the initial doses. Hexyon or another appropriate combination vaccine may be used for the booster.

Real-world equivalents: 2-3-4 months, 2-4-6 months, or WHO 6-10-14 weeks, with a booster at 12–24 months depending on national programmes.

Per the Hexyon EPAR:

• History of allergic reaction to Hexyon, to a vaccine containing the same components, or to substances used in manufacture which may be present at trace levels (such as the antibiotics neomycin or streptomycin).
• Encephalopathy (a brain disease) of unknown cause within 7 days of receiving a vaccine containing pertussis components in the past.
• Uncontrolled or severe illness affecting the brain or nervous system, such as uncontrolled epilepsy, unless the condition has stabilised with treatment and the benefit clearly outweighs the risk.

Defer vaccination if the child has a moderate or severe fever.

Precautions (not absolute contraindications):

• Temperature ≥40.5°C within 48 hours of a previous pertussis-containing vaccine.
• Collapse or shock-like state within 48 hours.
• Persistent inconsolable crying ≥3 hours within 48 hours.
• Seizures within 3 days of a previous pertussis-containing vaccine.
• Guillain-Barré syndrome within 6 weeks of a previous tetanus-containing vaccine.
• Bleeding disorders (use precautions for IM injection).

Not contraindications: minor illness, mild local reaction to a previous dose, family history of seizures, family history of post-vaccination adverse events, stable neurological conditions (cerebral palsy, controlled seizures, developmental delay), prematurity (use chronological age), breastfeeding.

Most adverse events are mild and resolve within a few days.

Very Common (>10%): injection site pain, redness, swelling, induration; irritability/fussiness; crying; drowsiness; loss of appetite; low-grade fever.

Common (1–10%): injection site nodule, diarrhea, vomiting, unusual crying, restlessness, fever >38°C.

Uncommon (0.1–1%): upper respiratory tract symptoms, cough, extensive limb swelling (especially after booster doses), high fever (≥39.6°C).

Rare (<0.1%): allergic reactions (rash, urticaria), febrile seizures, hypotonic-hyporesponsive episode (HHE — rare, self-limiting), thrombocytopenia.

Very Rare: anaphylaxis, afebrile seizures, encephalopathy (causality not established), brachial neuritis.

Post-vaccination apnea: in very premature infants (≤28 weeks gestation), monitor for 48–72 hours after the first dose. Benefits of vaccination still outweigh risks.

Route

Deep intramuscular injection only — normally into the upper thigh or shoulder, per the Hexyon EPAR. Do not administer subcutaneously, intradermally, or intravenously.

Injection Site

• Preferred in infants: anterolateral thigh (vastus lateralis muscle).
• Never use the buttocks: risk of sciatic nerve injury and reduced immunogenicity.
• Older children: deltoid is acceptable.

Procedure

• Inspect the vaccine visually; shake well before use to form a uniform turbid white suspension. Do not use if discolored or contains particles.
• Use a 22–25 gauge needle of appropriate length (typically 7/8 to 1 inch for infants).
• Insert at 90° angle. Aspiration is no longer recommended.
• Inject the entire 0.5 mL dose. Apply gentle pressure (do not rub).

Bleeding Disorders

Administer with a fine needle (≥23 gauge), apply firm pressure for ≥2 minutes, and do not massage the injection site.

Co-Administration

Can be given simultaneously with all other recommended childhood vaccines (pneumococcal conjugate, oral rotavirus, MMR, varicella, meningococcal vaccines) at separate injection sites or, if necessary, in the same limb at least 1 inch apart, using separate syringes.

Interchangeability

Completing the series with the same brand is preferred. If unavailable, other DTaP-containing combination vaccines may be used to complete the series — completion of the series is more important than brand consistency.

Interrupted Schedule

Continue the series where left off. Do not restart. Longer intervals between doses do not reduce final immunity (only delay protection).

• Immunosuppressive therapy: may reduce immune response. Vaccinate where benefits outweigh reduced response. Consider antibody titer testing in some cases.
• Immunoglobulin or blood products: do not interfere with inactivated vaccines; can be administered concurrently.
• Other recommended childhood vaccines: no interference; co-administration is safe and effective.

Pre-Vaccination Assessment

Review medical history, assess for contraindications and precautions, ask about reactions to previous doses, and ensure the infant is healthy enough for vaccination.

Apnea in Premature Infants

Infants born ≤28 weeks gestation are at higher risk of apnea after the first dose. Vaccinate in a setting where respiratory monitoring is available and observe for 48–72 hours after the first dose. Benefits still outweigh risks.

Post-Vaccination Care

• Observe for 15 minutes after vaccination for allergic reactions.
• Acetaminophen or ibuprofen may be used for fever or discomfort. Prophylactic antipyretics may reduce immune response — give only if fever occurs.
• Cool compress for swelling.
• Seek medical attention for: fever ≥40.5°C, seizure, persistent inconsolable crying >3 hours, limpness or unresponsiveness, severe allergic reaction symptoms.

Seizure History

Family history of seizures is not a contraindication. Personal history: vaccinate if controlled; contraindicated if uncontrolled or progressive neurological disorder. Consult with a neurologist as appropriate.

Immunocompromised Infants

Safe to administer (inactivated components). May have reduced immune response. Consult with a specialist; antibody testing may be considered to confirm immunity.

Record Keeping

Document date, vaccine name, manufacturer, lot number, site and route of administration, person administering vaccine, and any adverse events.

Store at 2–8°C in the original package, protected from light. Do not freeze (discard if frozen). Maintain cold chain throughout transport and storage. Monitor refrigerator temperature daily and avoid storage in the refrigerator door.

Before administration, remove from the refrigerator just before use, check the expiry date, and shake well.

Typically 3 years when stored properly. Do not use after the expiry date printed on the label.

Prescription required. Available at pediatric clinics, healthcare facilities, and immunization centers. Must be administered by qualified healthcare professionals.