Exploring Bioethics - NIH Office of Science Education - National ...

23. Ask all students to hold up their cards. On the transparency,record the number of people infected under Day 3. Students whowill die if they become infected should be recorded as infected if theyare tagged, and they should not tag anyone else.Tip from the FieldIf the disease does not spread atall, or if it continues through thepopulation without stopping, youshould decrease, or increase, thenumber of vaccinated individualsand repeat the simulation. You maywish to have some additional cardscopied in advance for this purpose.Tip from the FieldYou may wish to have everyoneread their vaccination status cardsaloud and note whether they gotthe disease or not.24. Continue until the disease stops spreading. Some of the susceptiblepeople should not get sick because of the presence of vaccinated people.25. Ask students to record the Round 2 class data on their copies ofMaster 2.8.26. In a whole-class discussion, ask students to describe theirobservations about how the disease spread in Round 2 comparedwith Round 1. Briefly discuss what happens when enough studentsare immune to prevent the spread of the disease throughout thepopulation: many susceptible people will be protected.27. Then, discuss the reasons for why some students were susceptible.Ask all the students who were susceptible but didn’t get thedisease to stand up and read aloud the information on theirvaccination status cards.Activity 4:Discussing the SimulationEstimated Time: 30 minutesProcedure1. Debrief the community immunity activity with students by askingthem how the course of the disease differed in the different rounds.2. Develop a working definition of the concept of communityimmunity.NoteIn this module, the termcommunity immunity is favoredover herd immunity to emphasizethe implications that populationvaccination levels have for thecommunity as a whole.Community immunity: When a critical percentage of a populationis immune to a particular transmissible disease (in this case, throughvaccination), the disease can no longer circulate in the community.You may want to draw on the following points as the class developsthe definition:• The concept of community immunity applies only to diseases that arereadily transmissible between people. It does not apply to diseases,such as tetanus, that are not transmissible between people.• As the simulation illustrated, when community immunity isachieved, the chances that a nonvaccinated person gets a diseaseare greatly diminished. There are vastly fewer people from whom anunvaccinated person can contract a virus.2-18 Exploring Bioethics