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Worksheet: Preventing Outbreaks with Herd Immunity

Part 1: What is community immunity and who does it help?

  • First watch this video: How does herd immunity work?
  • Next, navigate to the Preventing Outbreaks with Herd Immunity Notebook at SimPandemic. SimPandemic is an online simulator that lets you explore how various factors change a pandemic's evolution. Read through scenarios 1-2 and study the accompanying graphs.
  • Use the information in the video and the SimPandemic Notebook to answer questions 1-5.
1. In your own words, explain what community immunity (also called "herd immunity" or "herd protection" in the video) is
2. Which of these groups of people increase community immunity? Mark all that apply.
3. Fill out the Outcomes for Scenarios 1-2 based on the graphs and tables in scenarios 1-2 in the SimPandemic Notebook. You will use this information to support your claims in other questions. (Note: SimPandemic reports economic outcomes of the pandemic, too. While this feature is not used in this lesson, you might find it interesting to take a look at.)

Scenario 1: COVID-19 Outbreak with No Interventions

Outcomes:
Epidemic Size (Total Infections per 100,000)
Hospitalized (% of capacity)
Total Deaths Caused by Pandemic per 100,000
Total Number Immune per 100,000 on Day 1
Total Number Immune per 100,000 on Day 365

Scenario 2: COVID-19 with 30% Community Immunity

Outcomes:
Epidemic Size (Total Infections per 100,000)
Hospitalized (% of capacity)
Total Deaths Caused by Pandemic per 100,000
Total Number Immune per 100,000 on Day 1
Total Number Immune per 100,000 on Day 365

4. Does having 30% of the community already immune to COVID-19 protect the population from a new COVID-19 outbreak? Support your claim(s) using evidence from your answers from Question 3.
5. Name at least three groups of people who community immunity might help protect.

Part 2: What does it mean to reach the herd immunity threshold?

  • In this part, you will use the Sandbox to run your own simulations with settings you put in. If you have questions about how to use the Sandbox, read the FAQ.
  • Make sure to save your work as you go (see FAQ).
  • When you have completed all your simulations, paste (or write) the URL for them here for your teacher to see
  • Use what you learn from your own simulations to answer questions 6-9.
6. Follow the instructions in the Sandbox to run a simulation of COVID-19 transmission in a community where 50% of the population is immune. Does an outbreak still occur? If so, is the outbreak better or worse than in scenario 2 when there was 30% community immunity? Give evidence to support your claim.
7. In your own words, what is the herd immunity threshold of a disease?
8. Follow the instructions in the Sandbox to find the herd immunity threshold for COVID-19. Based on your simulations, what is the herd immunity threshold for COVID-19?
9. Based on the simulations you ran and what you know about the COVID-19 pandemic, do you think it is a good idea to achieve COVID-19 herd immunity naturally by letting people get infected and passing it along, unchecked, to others? Why or why not? Explain your reasoning using data and facts.

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