Haemophilus Influenzae Vaccines
Introduction to Haemophilus Influenzae Vaccines
Haemophilus influenzae type b (Hib) vaccines are crucial immunizations that protect against severe bacterial infections caused by Haemophilus influenzae type b. These vaccines have dramatically reduced the incidence of invasive Hib disease since their introduction in the 1980s.
Key points:
- Hib vaccines specifically target Haemophilus influenzae type b, not other types of H. influenzae or influenza viruses.
- They are a critical component of routine childhood immunization programs worldwide.
- The vaccines work by inducing immunity against the capsular polysaccharide of Hib.
- Several formulations exist, including monovalent Hib vaccines and combination vaccines that include Hib components.
Understanding the characteristics of Hib disease and the specifics of these vaccines is essential for healthcare providers to ensure optimal patient care and public health outcomes.
Haemophilus Influenzae
Microbiology:
- Gram-negative coccobacillus
- Facultative anaerobe
- Six encapsulated serotypes (a-f) and non-typeable strains
- Type b is the most virulent and was the most common cause of invasive disease pre-vaccination
Virulence Factors:
- Polysaccharide capsule (major virulence factor for type b)
- Pili and adhesins for attachment
- IgA protease
- Lipooligosaccharide (endotoxin)
Epidemiology:
Before widespread vaccination, Hib was the leading cause of bacterial meningitis in children under 5 years old. Incidence has dramatically decreased in countries with routine Hib vaccination programs, but remains a significant problem in areas with low vaccination rates.
Hib Disease
Clinical Manifestations:
- Meningitis (most common invasive form)
- Epiglottitis
- Pneumonia
- Septic arthritis
- Cellulitis
- Bacteremia
- Otitis media
Pathophysiology:
Hib typically colonizes the nasopharynx. In susceptible individuals, it can invade the bloodstream and spread to other parts of the body. The polysaccharide capsule helps the bacteria evade the host immune system.
Risk Factors:
- Age (children under 5, especially those between 6-18 months)
- Lack of vaccination
- Immunodeficiency
- Asplenia
- Sickle cell disease
- Native American or Alaska Native ethnicity
Diagnosis:
Culture of sterile body fluids (blood, CSF), supported by rapid antigen detection tests and PCR.
Hib Vaccines
Types of Hib Vaccines:
- Monovalent Hib vaccines:
- PRP-T (e.g., ActHIB, Hiberix)
- PRP-OMP (e.g., PedvaxHIB)
- Combination vaccines containing Hib:
- DTaP-IPV/Hib (e.g., Pentacel)
- DTaP-HepB-IPV/Hib (e.g., Hexaxim, Infanrix Hexa)
Vaccine Components:
- Hib capsular polysaccharide (polyribosylribitol phosphate, PRP)
- Carrier protein:
- Tetanus toxoid (T)
- Outer membrane protein complex of Neisseria meningitidis (OMP)
- CRM197 (mutant diphtheria toxin)
- Adjuvants (e.g., aluminum salts)
- Preservatives and stabilizers
Mechanism of Action:
Hib vaccines induce the production of antibodies against the capsular polysaccharide of Hib, providing protection against invasive disease. The carrier protein enhances the immune response, especially in young children.
Administration of Hib Vaccines
Recommended Immunization Schedule (USA):
- Primary series:
- 2, 4, 6 months (if PRP-T vaccine is used)
- 2, 4 months (if PRP-OMP vaccine is used)
- Booster: 12-15 months
Administration Technique:
- Route: Intramuscular injection
- Site:
- Infants: Anterolateral thigh
- Older children: Deltoid muscle
- Needle length and gauge: Adjust based on patient's age and size
Catch-up Immunization:
For unvaccinated children aged 7-59 months, catch-up schedules vary based on age. Consult current immunization guidelines for specific recommendations.
Storage and Handling:
Store refrigerated between 2°C to 8°C (36°F to 46°F). Do not freeze. Protect from light.
Side Effects of Hib Vaccines
Common Side Effects:
- Local reactions:
- Pain, redness, and swelling at the injection site (up to 25% of recipients)
- Usually mild and self-limiting
- Systemic reactions:
- Fever (usually low-grade, in about 2% of recipients)
- Irritability
- Drowsiness
- Loss of appetite
Rare Side Effects:
- Severe allergic reaction (anaphylaxis): Extremely rare, less than 1 per million doses
- High fever (>39°C or 102.2°F): Very rare
- Seizures: Extremely rare
Management of Side Effects:
- Local reactions: Cold compresses, pain relievers if needed
- Fever: Antipyretics as needed (e.g., acetaminophen, ibuprofen)
- Severe reactions: Immediate medical attention and reporting to vaccine adverse event reporting systems
Note: The benefits of Hib vaccination far outweigh the risks of side effects for the vast majority of individuals.
Contraindications and Precautions for Hib Vaccines
Absolute Contraindications:
- Severe allergic reaction (e.g., anaphylaxis) to a previous dose or any vaccine component
- Age younger than 6 weeks
Precautions:
- Moderate or severe acute illness with or without fever
- History of Guillain-Barré syndrome within 6 weeks of a previous dose of tetanus toxoid-containing vaccine (for combination vaccines containing Hib and tetanus toxoid)
Not Contraindications:
- Mild acute illness with or without low-grade fever
- Current antimicrobial therapy
- Recent exposure to an infectious disease
- History of penicillin or other nonspecific allergies
- Family history of adverse reactions to vaccines
Always consult the most current immunization guidelines and vaccine package inserts for the most up-to-date information on contraindications and precautions.
Hib Vaccination in Special Populations
Immunocompromised Individuals:
- May receive Hib vaccine, but immune response may be suboptimal
- Additional doses may be recommended for certain conditions (e.g., asplenia, HIV)
Asplenia:
- Individuals with anatomic or functional asplenia are at increased risk for invasive Hib disease
- If not previously immunized, should receive at least one dose of Hib vaccine
Hematopoietic Stem Cell Transplant Recipients:
- Should receive three doses of Hib vaccine, starting 6-12 months after successful transplant
HIV-Infected Individuals:
- Should receive Hib vaccine according to the routine schedule
- Previously unvaccinated HIV-infected children 5-18 years old may receive one dose of Hib vaccine
Preterm Infants:
- Should receive full doses of Hib vaccine on the same schedule as term infants, based on chronological age
Adults:
Routine Hib vaccination is not recommended for healthy adults. However, it may be given to adults with certain high-risk conditions (e.g., asplenia, hematopoietic stem cell transplant).
Haemophilus Influenzae Vaccines
- What is Haemophilus influenzae?
A bacterium that can cause severe infections, particularly in young children - What type of Haemophilus influenzae does the vaccine protect against?
Type b (Hib) - At what age is the first dose of Hib vaccine typically given?
2 months - How many doses of Hib vaccine are typically recommended for infants?
3 or 4 doses, depending on the specific vaccine brand - What diseases can Hib vaccine prevent?
Meningitis, pneumonia, epiglottitis, and other invasive diseases caused by Hib - Is the Hib vaccine a live vaccine?
No, it's a conjugate vaccine - Can adults receive the Hib vaccine?
Generally not recommended for healthy adults, but may be given to those with certain high-risk conditions - What is the efficacy of the Hib vaccine?
More than 95% effective in preventing invasive Hib disease - Can pregnant women receive the Hib vaccine?
Not routinely recommended, but can be given if high risk - What are common side effects of the Hib vaccine?
Redness, swelling, and warmth at the injection site; fever - Can the Hib vaccine be given with other vaccines?
Yes, it can be administered with other routine childhood vaccines - Is there a combination vaccine that includes Hib?
Yes, such as DTaP-IPV/Hib and DTaP-HepB-IPV/Hib - Who should not receive the Hib vaccine?
Infants younger than 6 weeks and people who have had a severe allergic reaction to a previous dose - What is the storage temperature for Hib vaccines?
2°C to 8°C (35°F to 46°F) - Can the Hib vaccine prevent all types of H. influenzae infections?
No, it only protects against type b - Is the Hib vaccine part of the routine childhood immunization schedule globally?
WHO recommends it, but implementation varies by country - Can immunocompromised individuals receive the Hib vaccine?
Yes, but they may have a reduced immune response - What organization recommends Hib vaccination globally?
The World Health Organization (WHO) - In which year was the first Hib conjugate vaccine licensed?
1987 - How long does immunity from the Hib vaccine last?
It's believed to provide long-lasting protection, possibly lifelong - Can the Hib vaccine be given to premature infants?
Yes, at the same chronological age as full-term infants - Is there a need for booster doses after completing the initial Hib vaccine series?
Generally no, except for certain high-risk individuals - Can the Hib vaccine be given to people with a history of Guillain-Barré syndrome?
Yes, Hib vaccine is not contraindicated in these individuals - How has the incidence of invasive Hib disease changed since vaccine introduction?
It has decreased by more than 99% in countries with routine vaccination - Can the Hib vaccine interfere with diagnostic tests for Hib disease?
No, the vaccine does not interfere with diagnostic tests - Is the Hib vaccine effective against antibiotic-resistant strains of Hib?
Yes, it's effective regardless of the bacteria's antibiotic sensitivity - Can the Hib vaccine be given to individuals with a latex allergy?
Check the specific vaccine, as some may contain latex in the packaging - What's the impact of Hib vaccination on herd immunity?
High vaccination rates can provide indirect protection to unvaccinated individuals - Can the Hib vaccine cause Hib disease?
No, it's not a live vaccine and cannot cause Hib disease - Is there a specific Hib vaccine for adults?
No, the same vaccine is used for all age groups when indicated
