2.2.2 The anti-bacterial components of pentavalent vaccine
Three of the antibacterial components in the pentavalent vaccine used routinely in the EPI in Ethiopia are known as DPT (diphtheria-pertussis-tetanus), referring to the three bacterial diseases they prevent. In Ethiopia, DPT is only given in the pentavalent vaccine, but some other countries give DPT as a separate injection. The fourth antibacterial component of the Ethiopian pentavalent vaccine is called Hib, which stands for Haemophilus influenzae type b. These four components are described below.
Diphtheria toxoid is a sub-unit antibacterial vaccine, made from the modified toxin (poison) produced by the bacteria Corynebacterium diphtheriae. The vaccine protects against diphtheria, a serious bacterial infection causing a sore throat, high fever and serious complications which can be fatal. It has become rare in Ethiopia and most other countries where infants are routinely vaccinated against it.
Pertussis vaccine is an inactivated antibacterial vaccine, which contains killed whole bacterial cells. It protects against pertussis (also known as whooping cough), a highly contagious, acute respiratory infection caused by the bacteria Bordetella pertussis.
Tetanus toxoid (TT)
Tetanus toxoid (TT) is a sub-unit antibacterial vaccine, made from the modified toxin produced by the bacteria Clostridium tetani. Tetanus is a disease that is acquired through exposure to the spores of these bacteria, which are universally present in the soil. TT vaccine is also given on its own as a ‘booster’ to women of childbearing age, and we will say more about this in Section 2.4.
Haemophilus influenzae type b (Hib)
Hib vaccine is a conjugate antibacterial vaccine, which protects against pneumonia and meningitis caused by the bacteria Haemophilus influenzae type b. These bacteria are the most common cause of bacterial meningitis in children under five years of age in countries where Hib vaccine is not routinely given to all infants. Meningitis refers to severe infection of the membranes surrounding the brain and spinal cord, which can rapidly lead to high fever, paralysis and death. Haemophilus influenzae type b bacteria are also the second most common cause of bacterial pneumonia in children. (In Section 2.3 you will learn about the vaccine that protects against Streptococcus pneumoniae, the most common cause of bacterial pneumonia in children.) Pneumonia is a severe infection in the lungs, which causes the air sacs to fill with fluid and pus; this makes breathing painful and difficult, and reduces the oxygen getting into the body. Note that Hib vaccine only protects against diseases caused by type b Haemophilus influenzae bacteria (there are other types), and it does not prevent pneumonia or meningitis caused by other infectious agents.
The fifth component of the pentavalent vaccine used in the EPI in Ethiopia protects against the viruses that cause hepatitis B liver disease; we will describe it in Study Session 3, together with the other antiviral vaccines in the Ethiopian EPI.