Using Vaccines to Fight Outbreaks

Background Information for Teachers

Vaccines are a key part of preventative medicine. They prime an individual's acquired immune system so that it has antibodies to recognize and fight off a potential pathogen without ever having to experience the harmful, or even deadly, symptoms of the disease.

There are several ways to create vaccines, including using weakened (sometimes called attenuated) versions of the pathogen, a dead pathogen, or only subunits of the pathogen that present antigens that the immune system can react against. All vaccines, regardless of how they are produced, have to go through extensive testing to prove both their effectiveness and their safety. Because vaccines are given to healthy people as a preventative measure, they are held to high standards of safety and probability that they provide more benefit than risk. Prior to approval, vaccines are tested in thousands of individuals to ensure there are no major side effects; minor side effects, like fever or muscle soreness, are okay.

In public health, vaccines are considered to act at two different levels: 1) the individual level and 2) the population level. As an individual, once you are vaccinated, immunity does not set in immediately. There is a period of several days or weeks during which your body may mount an immune response to the vaccine. If a vaccine is effective, this immune response will be sufficient to build long-term memory and immunity to the pathogen. During that time, individuals are not immune, and can still contract the disease, until the immune response has taken place. Furthermore, there is a chance that the vaccine will not work for an individual. A vaccine's effectiveness is measured by the percentage of people who successfully become immune. The effectiveness of the measles vaccine is approximately 98% after two doses. In contrast, the yearly vaccine for the flu virus has ranged from 10% to 60% since 2010.

For those who cannot be vaccinated (often infants or those who are immunocompromised) or for whom the vaccine is not effective (many vaccines are less effective in elderly populations), vaccines can still be helpful at a population level. How impactful vaccines are at a population level is directly correlated to both their effectiveness and the percentage of the population that has been vaccinated. The higher the percentage of vaccinated people in the population, the larger the pool of immune individuals. Immune individuals cannot catch or spread a disease and, subsequently, slow or even halt the spread of an outbreak. In this lesson plan, students will explore this phenomenon by running simulations using SimPandemic.

You will see that students obtain slightly different results, even when they have the same inputs for SimPandemic. Many events in the real world and in a simulation of the real world are based on chance. When you become infected in the real world, you often don't know when or where the infection occurred. Perhaps someone sneezed when you were randomly walking by them. A simulation cannot predict that you were going to get infected (except in special cases), but it can predict fairly well that someone would get infected. In SimPandemic there are many events where the simulation literally rolls virtual dice to determine when an infected individual will transmit the disease to another (all within the bounds specified by the input parameters). To better understand the assumptions and parameters involved in SimPandemic, read the FAQ.

Additional Background Links

• Vaccine Science: Vaccines and the Immune System, The Vaccine Education Center at Children's Hospital of Philadelphia
• Vaccine Safety: Are Vaccines Safe?, The Vaccine Education Center at Children's Hospital of Philadelphia
• Six common misconceptions about immunization, World Health Organization
• The race for coronavirus vaccines: a graphical guide, Nature Research

Prep Work (35 minutes)

1. Review the videos that students will be watching to learn about the adaptive immune system and vaccines.
   1. Immune System, Part 2: Crash Course
   2. How to Make a COVID-19 Vaccine
2. Familiarize yourself with the SimPandemic online software. Read through the SimPandemic FAQ and try out the Using Vaccines to Fight Outbreaks SimPandemic Notebook associated with this lesson.

Engage (10 minutes)

Remote learning adaptation: This lesson plan can be conducted remotely. Students can work independently on the Explore section of the lesson plan using the Student Worksheet as a guide. The Engage and Reflect sections can either be dropped entirely, done in writing remotely, or be conducted over a video chat.

1. Start by describing a scenario to your students and asking them for a scientific explanation. Record their answers to revisit at the end of the lesson.

   Imagine this scenario: There are two islands, island A and island B, each with similar populations in terms of size and demographics. No one has ever been infected with COVID-19 on either island because the islands closed their borders at the beginning of the COVID-19 pandemic. Now, months later, a vaccine has been developed for COVID-19. A team of workers first visits island A to vaccinate all of the residents with a vaccine, and then visits island B two weeks later to vaccinate all of their residents with the same vaccine. After the workers leave, residents on both islands agree to continue to keep their borders closed until the vaccine has been administered worldwide. Several months later, more than half of the residents on island A have contracted COVID-19, but no one on island B has contracted it. What is your scientific explanation for this phenomenon?

   Students may be puzzled. Encourage them to toss out hypotheses, regardless of whether they are right or wrong. Record all answers to revisit at the end of the lesson.

2. Tell students that they'll be learning more about how vaccines work and how they can affect the outcomes of an outbreak. At the end of the lesson, they will have a chance to try to solve this puzzle again using their new knowledge.

Explore (80 minutes)

1. Distribute either the Student worksheet PDF or the Student worksheet Quiz form to each student. Break the class into pairs if they will be collaborating on the worksheet.
2. Show students, or have them watch independently, the Immune System, Part 2: Crash Course video to learn more about how the adaptive immune system works. After the video ends, have them answer Student Worksheet question 1.
   

   https://www.youtube.com/watch?v=2DFN4IBZ3rI

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3. Show students the How to Make a COVID-19 Vaccine video to learn more about what vaccines are, how they work, and how they are made. After the video ends, have them answer Student Worksheet questions 2-4.
   

   https://www.youtube.com/watch?v=DcdZQHD4MJE
4. Discuss the answers to questions 1-4 as a class (a teacher Answer Sheet is available.) This ensures that all students have a good understanding of the biology behind vaccines before they are asked to apply that knowledge to the modeling and data analysis parts of the lesson. Alternatively, collect, grade, and return the worksheets before continuing.
5. Set up Part 2 of the lesson by asking students how a vaccine might affect the outcomes of a pandemic.

   How do you think the COVID-19 pandemic might have been different if a vaccine was available before the outbreak? How would a vaccine change outcomes for individuals and how would it change outcomes for larger populations?

   Based on their new knowledge about vaccines, students should be able to state that individuals who got the vaccine would largely be immune to COVID-19 and would not suffer the disease symptoms. Students may need prompting to expand their thinking to the population level, but with a bit of help should be able to conclude that if enough people are vaccinated and immune, they cannot pass along the disease and the outbreak quickly dies out.

6. Tell students they will be using an online tool called SimPandemic to model the impact of vaccination on a COVID-19 pandemic. Navigate to the Using Vaccines to Fight Outbreaks SimPandemic Notebook and review the information in the first section with students. In particular:
   1. Explain to students that this is what a model of the COVID-19 pandemic looks like if no interventions (no masks, no physical distancing, no shutdowns, etc.) looks like.
   2. Go over the For Simulated Populations of 100,000 outcomes table and how to read the accompanying graph. Make sure every student understands the type of data being presented before continuing. Also make sure that students understand that this graph models the question they were asked about how a vaccine administered before an outbreak can alter the course of an outbreak.
   3. Emphasize that the outcomes are listed per 100,000 individuals to enable direct comparisons between simulations of different scenarios.
   4. Point out the FAQ button. If students get stuck or have questions about the program, the SimPandemic FAQ is likely to have answers.
   5. Explain that if the simulation was run twenty times, each time the results would be slightly different. This is because the simulation mimics real life in that it looks at the chance of getting infected and the chance of having symptoms or dying. In SimPandemic there are many events where the code underlying the simulation literally rolls virtual dice to determine when an infected simulant will transmit the disease to another (all within the bounds specified by the input parameters). Just like rolling dice in a board game, the results can vary within a predictable statistical range.
7. Direct students to work independently, or in pairs, to read through the information in sections 1-3 of The Impact of Vaccines: COVID-19 notebook, and use the information provided there, as well as their analysis of the graphs and tables, to answer Student Worksheet questions 5-9.
8. Set up Part 3 of the lesson by reminding students that so far in SimPandemic they have been looking at models of how a highly effective vaccine (90% effectiveness) administered to most of the population (90%) affects the course of the outbreak. Ask students how they think the course of the outbreak might change if they had a less-effective vaccine or fewer people were vaccinated.

   When you compare the outcomes of a COVID-19 outbreak with no interventions (notebook section 1) and with an effective vaccine given during the outbreak to most of the population (notebook section 3) what changes between those two scenarios?

   Looking at the data, it is clear that the vaccine intervention makes the outbreak far less severe. There are decreases in the number of people infected, the number of symptomatic individuals, and the percentage of the population that dies from COVID-19. The hospitals are also less overwhelmed (although they do become overwhelmed).

   What do you predict would happen if the vaccine administered during the outbreak was less effective and fewer people were willing to be vaccinated? As public health official, would you still go through with the vaccination campaign? Would it be worthwhile for individuals? Would it be worthwhile for the population?

   Most students will predict that a less-effective vaccine given to fewer people will not be as effective at suppressing the outbreak. Students' answers are likely to vary regarding what they would do as a public health official. Particularly astute students might be able to distinguish that risk reduction on an individual level may be worthwhile for some people, but that as a population the impact on the outcomes of the outbreak will be minimal without more widespread vaccination.

9. Tell students that they will have the opportunity to test their predictions by exploring and running their own simulations. They will use the Sandbox in notebook section 4 to manipulate both the percent effectiveness of the vaccine and the percent of the population vaccinated, then run the simulation and see how the outbreak unfolds. Before letting students explore, consider going over with them:
   1. How to make changes to the settings.
   2. How to save their work in SimPandemic.
   3. Remind them that if they have questions they can always consult the FAQ.

Reflect (10 minutes)

1. Remind students of the scenario you laid out for them about the two islands (see the Engage section for details). Read back the explanations they originally came up with. Ask students what they now think the scientific explanation is.

   What is your scientific explanation for why over half of island A residents have contracted COVID-19, but none of island B residents have? Explain your reasoning.

   Based on their new knowledge and the data they generated by running models, students should be able to conclude that one or more of the workers who came to vaccinate the islanders were already infected with COVID-19 at the time they arrived on island A, and infected some residents. It is possible that the worker(s) were asymptomatic and did not know they had it. Furthermore, it is possible that the worker(s) may have even thought that they were immune because they had been vaccinated but, either a) because vaccines are not 100% effective, their body had never formed antibodies and they were not immune or b) because it takes awhile for vaccines to trigger immunity, and they simply caught COVID-19 before the vaccine took effect. Similarly, some residents on island A caught COVID-19 from the worker(s) despite being vaccinated because immunity from the vaccine had not yet developed at the time they were exposed. Vaccination campaigns take awhile to administer, so by the time the worker(s) arrived on island B, they'd had COVID-19 for long enough that they were no longer infectious and, in fact, were now immune. Thus, no one on island B was exposed to anyone with COVID-19; subsequently, none of them contracted the disease.

Assess

Students' worksheets can be used to assess their learning over the course of the lesson. Alternatively, you can have students write out their scientific explanations for the Scenario in the Reflect section.

Make Career Connections

Discussing or reading about these careers can help students make important connections between the in-class lesson and STEM job opportunities in the real world.

Epidemiologist

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Career Profile

Epidemiologists work to study, understand, and contain outbreaks. They often work in public health roles to help devise and implement procedures, like vaccination campaigns, that prevent outbreaks. When an outbreak occurs, they are on the front lines of dealing with the outbreak and in communicating life-saving information to the public. Read more

Microbiologist

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Career Profile

Microbiologists study microscopic organisms like bacteria, fungi, and viruses. Those with deep expertise in viruses may also be called virologists and are critical players in researching novel emerging viruses, like SARS-CoV-2. Microbiologists research how viruses are transmitted, how they replicate, and how they affect humans and other animals. Their expertise on the structure of viruses is important when developing a vaccine and they are important members of vaccine research groups. Read more

Lesson Plan Variations

• This lesson plan may be extended by asking students to write and model their own scenarios around a COVID-19 vaccine and outbreak.
• As information emerges on different COVID-19 vaccine candidates, students can plug that information into the model and explore possible outcomes.
• Have students research other well-studied pathogens and their vaccines— like flu, polio, or measles—and write and model scenarios around these diseases and what would happen at different levels of vaccine compliance.
• Several other SimPandemic lesson plans are available.