Overview of viral vaccine-preventable diseases
As you know from Study Session 1 of this Module, viruses are microscopic infectious agents that do not have the structure of a cell; they are more like tiny boxes or particles. They are much smaller than bacteria and can only be seen with the most powerful microscopes. Some of the diseases caused by viruses can be prevented by vaccination, as you will learn in this study session.
Do you know of any human communicable diseases caused by a virus?
HIV disease and AIDS are caused by the human immunodeficiency virus (HIV). You may also have thought of measles, polio or hepatitis.
HIV cannot be prevented by vaccination at the present time, but the other three viral diseases mentioned above are part of the Expanded Programme of Immunization (EPI) in Ethiopia and many other countries around the world (see Table 4.1). The composition of the vaccines, which contain dead or weakened viruses or fragments of their structure, and the routes of administration, are described in detail in the Immunization Module. In the following sections, we will look at each of these diseases in turn.
Table 4.1 Causes, transmission, symptoms, prevention and control methods for common viral vaccine-preventable diseases.
| Disease | Cause | Mode of transmission | Symptoms | Prevention methods |
|---|---|---|---|---|
| Measles | measles virus | Respiratory by coughing or sneezing | Cough, rash and fever | measles vaccination |
| Poliomyelitis | polio virus | Ingesting (faeco-orally) | A few children have paralysis of the legs or hands; many will not show symptoms | oral polio vaccination (OPV) |
| Hepatitis | hepatitis B virus | Direct contact with body fluids or blood, or sexually transmitted | Fever, yellow colouring of the white part of the eye; many children will not show symptoms | hepatitis B vaccination |