DTP VACCINE

DTwP is a trivalent vaccine containing diphtheria toxoid, pertussis vaccine (Whole Cell Pertussis), and tetanus toxoid. It is also referred to as triple antigen. This vaccine is aimed at inducing active immunity in children against diphtheria, tetanus and whooping cough (pertussis). 

It consists of toxoids of diphtheria and tetanus along with killed whole cell suspension of Bordetella pertussis. Each of the components can be given separately, but administering them in combination minimizes the number of injections and improves the immune response against toxoids because the pertussis bacilli act as an adjuvant.

Vaccine preparation and composition:
Each 0.5-mL dose is formulated to contain 6.7-12.5 Lf units of diphtheria toxoid, 5 Lf units of tetanus toxoid, and less than or equal to 16 opacity units of pertussis vaccine. The cells of Bordetella pertussis in DTP vaccine are inactivated either with formalin or treatment with 0.2% merthiolate at 4^oC for several months. Toxins are toxoided either by heating or treatment with formaldehyde.

Course of vaccine:  
Primary course of DPT immunization consists of three intramuscular injections at intervals of 4-6 weeks initiated before the age of six months. The first dose is usually started by 2 months of age. The primary dose is followed by a booster dose at the end of first year of life. Subsequent booster doses are given at five years of age and 10 years of age. DTwP is not recommended in children aged 7 years and older due to increased risk of side effects.
Even though the infant receives maternal antibodies against tetanus, the immunization is started by 2 months because there is very little maternal immunity against pertussis. Diphtheria and pertussis are uncommon after the age of 5 years but tetanus can occur at any age. Therefore a booster dose of tetanus toxoid is administered at school entry.

Side effects of vaccine:
The side effects, whenever seen are usually because of pertussis component in the vaccine. About 20% of the children, who receive the whole cell vaccine experience mild side effects such as local inflammation and fever. About 0.1% of infants experience convulsions soon after receiving the vaccine and in a very small number of cases (1 in 150,000) severe or irreversible brain damage may occur. Because of possibility of provocative poliomyelitis, it is advisable not to carry out routine immunization if poliomyelitis is active in the area.

Alternatives:
Beginning in 1996 several new acellular pertussis vaccines have been developed from purified components of B.pertussis. These multicomponent vaccines contain combinations of pertussis toxoid, filamentous hemagglutinin, pertactin, and the two types of fimbriae. The diphtheria-tetanus-pertussis vaccine using acellular pertussis is known as DTaP. It is possible to combine the DTaP vaccine with the vaccine against Haemophilus influenzae type b (Hib). This vaccine is called DTaP/Hib.