• Due to their age at the time of the Covid-19 pandemic, some current high school students may have limited awareness of the severity of the disease when it first broke out, before humanity had built up more resistance to it. It’s important to ground the lesson in the numbers and video shown in the first slides of the slide deck, which give a very real sense of the initial severity and toll of the disease.
• At the same time, it’s important to emphasize that the first Covid-19 vaccines were created, tested, and approved in less than a year – a rapid timeline that broke records. For many, this was seen as a scientific breakthrough. However, for others, the rapid timeline created skepticism. In that short timeline, how did scientists establish that the vaccines actually worked? That’s what we explore in the lesson.
• This lesson addresses vaccine efficacy. However, another important question that students might bring up is vaccine safety. When subjects are randomly assigned a new vaccine or a placebo, researchers monitor for severe side effects in the vaccine group. In the Moderna vaccine trial, they found that “serious adverse events were rare, and the incidence was similar in the two groups.” Hence, they concluded that “aside from transient local and systemic reactions, no safety concerns were identified.”
• This lesson serves as an overview for the remainder of the unit, featuring the most important ideas from sampling and experiments. As such, it introduces many new concepts and vocabulary terms. You can let students know that many of the ideas they encounter, including investigative questions, confounding variables, sampling design, experimental design, and generalizability, will be covered again in later lessons. At this stage, the general intuition and framing is more important than mastering each individual concept.

First, download this lesson's Handout Key and read through its Discussion Question section. Then, check out our model discussion norms and the additional background notes below.

• In the original Moderna vaccine trial among adults, the estimated vaccine efficacy was 94.1%. In a follow-up trial among children, the vaccine was found to be 36.8% effective for 2-to-5-year-olds and 50.6% effective for 6-to-23-month-olds. So, the efficacy was substantially higher among adults than among young children. This provides an excellent teaching example of how the study results (94.1% effectiveness) only fully generalize to people similar to those studied in the original trial (adults).
• Even though the vaccine efficacy among children is lower, it’s still not 0. So, the vaccine still provides some level of protection for children. For extra background, here’s a lesson from the New York Times that shows the math behind calculating vaccine efficacy.

• The CDC has several ways of estimating the death toll from respiratory diseases. In the lesson, we use the most conservative CDC figures, which come from counts of official patient death certificates. This likely provides an underestimate of the true number of flu and covid-related deaths, which are likely underreported on death certificates.
• The studies for each major Covid-19 vaccine can be found here (linked): Moderna, Pfizer, and Johnson & Johnson.
• Students may need further explanation of asymptomatic, symptomatic, and severe cases. Asymptomatic cases are ones in which the infected individual does not feel sick; yet, they’re still infected and can spread the disease. In symptomatic cases, the individual feels sick, but they’re not in critical condition. In severe cases, the individual is in critical condition.
• The main trial discussed in this lesson – the Moderna vaccine trial – found that “aside from transient local and systemic reactions, no safety concerns were identified.” However, patients were monitored for a limited amount of time. What about potential side effects that could emerge 10, 20, or 30 years after taking the vaccine? According to immunology experts, in the history of vaccines, no vaccines have ever produced long-term side effects that only emerge years after injection. Instead, all side effects (including rare ones) emerge within 6-8 weeks of injection. Further, the body quickly breaks down the mRNA strands introduced by the Moderna vaccine within a few hours or days after injection.

• The topic of investigative questions will be refined throughout our course. In later units, we’ll add language for parameters. In the inference units, we’ll also start differentiating the question structure for confidence intervals and for hypothesis tests. For now, sticking to the simpler investigative question structure introduced in this lesson will help build intuition, without overwhelming students with too many details at once.
• Common synonyms for the explanatory variable include factor, independent variable, predictor, feature, or input. Common synonyms for the response variable include dependent variable, target, or output.
• The term “direct observation” is not included in the AP Statistics CED and will not show up on the AP Exam. However, it’s a common term in the field. It’s also pedagogically useful as a way to define observational studies that don’t utilize surveys.
• The main outcome measured in vaccine trials is vaccine efficacy. For extra background, here’s a lesson from the New York Times that shows the math behind calculating vaccine efficacy.
• It’s important to emphasize that generalizability requires not just random sampling, but also sampling from the correct target population. If we randomly sample from the wrong population or from just a subset of the target population, we cannot generalize our results to the whole target population.