Self-Assessment Questions for Study Session 1

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the Notes on the Self-Assessment Questions at the end of this Module.

SAQ 1.1 (tests Learning Outcomes 1.1 and 1.2)

When the immunization coverage rate is high, the herd immunity of a community is increased. Explain what this means and how everyone in the community benefits from it — including people who are not immune — in the case of a disease like measles, which is transmitted from person to person.


When the immunization coverage rate is high, a large proportion of the members of a community will be immune to the disease caused by the particular infectious agent in the vaccine. This is called herd immunity. Therefore, in a disease like measles, which is transmitted from person to person, there will be a very small reservoir of infection restricted to a few infected people in the community. Transmission of infection from infected to susceptible people will very rarely occur, so the infectious agent will not be able to spread through that community and it may even ‘die out’. This protects the susceptible people even though they are not immune.

SAQ 1.2 (tests Learning Outcomes 1.1 and 1.2)

You see a breastfed baby who appears to be immune to measles, even though he has not been vaccinated. His older brother has measles, but the baby has not developed the illness. How can this happen, and what is this type of immunity called?


Some immunity can be acquired without vaccination. This infant has become temporarily immune to measles because he has received maternal antibodies in his mother’s breastmilk (and possibly also across the placenta before he was born). This type of immunity is called naturally acquired passive immunity (‘passive’ because the antibodies protecting the baby were made by his mother, not by his own immune system).

SAQ 1.3 (tests Learning Outcomes 1.1, 1.2 and 1.3)

  • a.What type of vaccine is the diphtheria component of the pentavalent vaccine?
  • b.Explain how immunization with the pentavalent vaccine gives protection from diphtheria.
  • c.What is this type of immunity called?


  • a.The diphtheria component of the pentavalent vaccine is made from the toxin (poison) produced by the bacteria that cause the disease; the modified toxin is called diphtheria toxoid. This is an example of a sub-unit vaccine.
  • b.The diphtheria toxoid in the vaccine has antigens in its structure which are unique to the diphtheria bacteria. Helper T cells in the immune system of the immunized person recognise these antigens as foreign. They activate other parts of the immune system to make antibodies and memory cells, which remain circulating in the body for a long time. If live diphtheria bacteria get into the body, the person’s immune system is already prepared to attack them and prevent the disease from developing.
  • c.This type of immunity is called artificially acquired active immunity, where a vaccine is used to develop active immunity against an infection (‘active’ because the antibodies and memory cells were made by the person’s own immune system).

SAQ 1.4 (tests Learning Outcome 1.4)

The EPI was started many years ago, but it did not reach its original target of increasing the immunization coverage rate by 10% every year. The EPI has drawn up strategies to improve the immunization service in Ethiopia. How can you help to implement these strategies?


There are many ways in which you can help to implement the EPI services. You may have thought of the following:

  • Help to increase immunization coverage rates by using every opportunity to immunize eligible children, for example, when they are brought to the Health Post for another reason; and by making immunization routinely available at convenient times, preferably on a daily basis.
  • Ensuring the community is made aware of when immunizations are available. Use any strategies you can to sustain high immunization coverage, e.g. reminders, posters, meetings, etc.
  • Increase the quality of immunization services through good management, stock control and safe storage of vaccines and other supplies, and using safe injection practices and disposal of waste.
  • Help to reduce missed opportunities for immunization by checking if all eligible children that you see are immunized, and tracing defaulters (children who have not completed all the vaccinations in the schedule).
  • Help to improve public awareness and community participation in the immunization service by involving community leaders and groups in planning outreach sessions, so as to cover as much of the target population as possible.
  • Keep an accurate register of immunizations and report any cases of vaccine-preventable diseases to the District Health Office.

Summary of Study Session 1