Rationale
This vaccine is formulated to fight against three diseases – tetanus, diphtheria, and pertussis. The purpose of having three vaccines in one vial is convenience. In one sitting the recipient gains protection from all three diseases.

Tetanus is a neurological disease which can prove fatal. Diphtheria, on the other hand, produces toxins which could cause myocarditis, polyneuritis, and other systemic effects. Obstruction of the respiratory tract, presenting as tachypnea, dyspnea, stridor, cyanosis; and use of accessory muscles of respiration; can be caused by extensive pseudomembrane formation and swelling during the first few days of the disease.

Pertussis is a respiratory tract infection caused by Bordetella pertussis. Its most common presentation among adolescents and adults is a cough, with or without paroxysms, persisting for 2 weeks or more. Other useful clinical clues are shortness of breath during coughing spells, nocturnal cough, tingling sensation in the back of the throat, vomiting, and a history of exposure to other patients with a prolonged coughing illness. The life-threatening complication of this disease is pneumonia.

Generic and brand names
The generic name is Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis Vaccine Adsorbed. The brand name is Adacel or Boostrix.

Composition of the vaccine
The vaccine is a sterile, uniform, cloudy, white suspension of tetanus and diphtheria toxoids adsorbed separately on aluminium phosphate, combined with acellular pertussis vaccine and suspended in water for injection. The acellular pertussis vaccine is composed of 5 purified pertussis antigens (PT, FHA, PRN, and FIM).

Mechanism of action
When the vaccine is injected into you, there will be development and generation of neutralizing antibodies against tetanus and diphtheria toxins. At the same time, there will also be a production of antibodies against pertussis.

Schedule of administration
The first dose is given at the selected date. Revaccination can be done after 5 years if traveling to a foreign country, or 10 years if staying within the United States.

Indications and usage
This vaccine is indicated for active booster immunization for the prevention of tetanus, diphtheria, and pertussis (whooping cough) in persons 4 years of age and older. Persons who have had tetanus, diphtheria or pertussis should still be immunized since these clinical infections do not always confer immunity. Human Immunodeficiency Virus (HIV)-infected persons, both asymptomatic and symptomatic, should be immunized against tetanus, diphtheria, and pertussis according to standard schedules.

Precautions

• Do not administer by intravascular injection: ensure that the needle does not penetrate a blood vessel.
• Intradermal or subcutaneous routes of administration should never be used.
• It should not be administered into the buttocks.
• Vaccination should be postponed in cases of an acute or febrile disease. However, a disease with low-grade fever should not usually be a reason to postpone the vaccination.
• Because any intramuscular injection can cause an injection site hematoma in persons with any bleeding disorders, such as haemophilia or thrombocytopenia, or in persons on anticoagulant therapy, intramuscular injection with this vaccination should not be administered to such persons unless the potential benefits outweigh the risk of administration. If the decision is made to administer this vaccine by intramuscular injection to such persons, it should be given with caution, with steps taken to avoid the risk of hematoma formation following injection.
• The possibility of allergic reactions in persons sensitive to components of the vaccine should be evaluated. Hypersensitivity reactions may occur following the use of this vaccine even in persons with no prior history of hypersensitivity to the product components. As with all other products, epinephrine hydrochloride solution (1:1000) and other appropriate agents should be available for immediate use in case an anaphylactic or acute hypersensitivity reaction occurs. Health-care providers should be familiar with current recommendations for the initial management of anaphylaxis in non-hospital settings, including proper airway management.
• Immunocompromised persons (whether from disease or treatment) may not achieve the expected immune response. If possible, consideration should be given to delaying the vaccination until after the completion of any immunosuppressive treatment. Nevertheless, vaccination of persons with chronic immunodeficiency such as HIV infection is recommended even if the immune response might be limited.
• This vaccine should not be administered to individuals with progressive or unstable neurological disorders, uncontrolled epilepsy or progressive encephalopathy until a treatment regimen has been established, the condition has been stabilized, and the benefit clearly outweighs the risk;
• The effect of this vaccine on the development of the embryo and fetus has not been assessed. Vaccination in pregnancy is not recommended unless there is a definite risk of acquiring pertussis. As the vaccine is inactive, a risk to the embryo or the fetus is improbable. The benefits versus the risks of administering the vaccine during pregnancy should be carefully evaluated when there is a high probable risk of exposure, either due to a household contact or during an outbreak in the community.
  · The effect of this vaccine during lactation has not been assessed. Since this vaccination is inactive, any risk to the mother or the infant is improbable.

Side effects
The side effects noted after the first injection with this vaccine were the following:

• Injection site reactions (pain, swelling, erythema)
• Systemic reactions (Fever, headache, nausea, diarrhea, vomiting, anorexia, rash, body ache or muscle weakness, sore or swollen joints, tiredness, malaise, chills, axillary lymph node swelling.
• The side effects noted after the re-administration of this vaccine at 5 and 10 years were the following:
  • Injection site reactions (pain, erythema/redness, swelling).
  • Systemic reactions (fever, headache, myalgia, malaise).

Dosage and mode of administration
The single dose vaccine consists of 0.5 ml which are given as a booster by intramuscular route. Re-dosing with this vaccine can be used to boost immunity to diphtheria, tetanus, and pertussis at 5 to 10-year intervals. The preferred site of injection is the deltoid muscle.