Establishing Vaccination Policies Day 2: Community Immunity

Warmup Get out your green “Key Questions” worksheet Update the “Relevant Facts” section with the following key points: Chances of contracting disease, and harm from disease VARIES Vaccine risks are low (a few exceptions) Childhood infectious disease has been nearly eliminated due to vaccinations Sometimes outbreaks occur due to vaccine failure or because people have not been vaccinated Every state allows at least one type of exemption to mandatory vaccination policy (medical, religious, philosophical)

Reminder… Test Friday Study: Chapter 19: Virus and Bacteria Chapter 40: Immune System Study: Learning Targets Reading Guides Immune response worksheet (blue) Blood Type chart

Community Immunity The simulation demonstrates why people might choose not to be vaccinated and addresses the possible implications of their actions for the greater community

Community Immunity Simulation Overview Shows the spread of a hypothetical disease in a population. There are two rounds: Round One: everyone is susceptible to the disease Round Two: a majority of the people in the community are immune, but some are susceptible for various reasons After each day, you will hold a red (sick) or yellow (healthy)card and record results in your data sheet

Ground Rules for CI Simulation You are infectious for one “day” only When you are infectious, you infect two other students The index (first) case will tag two individuals sitting nearby, who will then become sick Anyone who is infected gets sick and remains sick In each day that follows, anyone who is newly sick (has just been tagged) tags two additional people Vaccinated people cannot tag anyone

Red = sick Yellow = healthy Round 1: Everyone is susceptible

Round 1 Summary When everyone is susceptible (no one is immune)… a disease spreads quickly through a population

Round 2 Some individuals are immune Read your Vaccination Status Card and keep it secret About 65% of students are vaccinated If you are TAGGED and you are… …SUSCEPTIBLE, you become INFECTED …IMMUNE, you do not become infected …SUSCEPTIBLE and DIE, you become INFECTED, but you CANNOT TAG anyone else

Round 2 Summary How was the spread of the disease different in round 2 than in round 1? When enough people are immune to prevent the spread of the disease throughout the population… many susceptible people will be protected Who was susceptible but did not get the disease?

Let’s Discuss… What is community immunity? When a critical percentage of a population is immune to a particular infectious disease (through vaccination), the disease can no longer circulate in the community Chances that a non-vaccinated person gets a disease are greatly diminished. There are far fewer people from whom an unvaccinated person can contract the virus However, the risk is not entirely eliminated. Parents who opt out of vaccinations reduce overall community immunity and place their own children at risk

Let’s Discuss… Is it fair? Benefits and risks of the vaccine: are they shared equally among the vaccinated and unvaccinated?

Let’s Discuss… What would happen in the number of vaccinated people increased? Decreased? What does this simulation reveal about protecting the most vulnerable members of the population: babies too young for vaccinations, people who don’t have good access to health care, etc. Are vaccination programs designed to protect the individual, community, or both?

Let’s Discuss… How might characteristics of the disease and vaccine affect community immunity? The percentage of vaccinated people in the community for community immunity varies Mumps: 75-86% Pertussis: 94% Smallpox: 85% Polio: 80-86%

Relevant Facts Add a sentence about community immunity to your “Relevant Facts” section Community immunity occurs when a large percentage of the population is vaccinated. It can prevent disease from becoming widespread and protects those who cannot be or choose not to be vaccinated.

Who are the stakeholders? When considering the question: “Under what circumstances should a state grant exemptions to its school vaccination policy?”, who has an interest in this issue? School Parents Students Teachers Medical community Larger community School board State public health department Others?

Community Immunity Reflection Answer questions #1-3

Online Community Immunity Simulator National Institutes of Health Office of Science Education Website http://science.education.nih.gov/supplements/nih1/diseases/activities/activity4.htm