## 1. Introduction

## 2. Methods

#### 2.1. Model Structure

#### 2.2. Model Feedback

#### 2.3. Model Behavior

^{2}= 0.999 for total cases and R

^{2}= 0.998 for deaths).

## 3. Results and Discussion

#### 3.1. Impact of Behavioral Feedback Loops

#### 3.2. Impact of People Being Less Careful

#### 3.3. Impact of the No-Mask Policy Partway through the Vaccination Program

#### 3.4. Impact of Delayed Vaccines

#### 3.5. Impact of Approving the Vaccine for a New Age Group

#### 3.6. Summary

## 4. Conclusions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Appendix A. Model Equations without Calibration Settings

**Stocks:**

**Flows:**

**Parameters and other variables:**

**Graphical functions:**

## References

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**Figure 6.**Vaccine hesitancy from fear of the vaccines not being safe decreases with the fraction of people vaccinated.

**Figure 7.**Full system diagram including all behavioral loops. All connections to vaccinating susceptible also go to vaccinating recovered.

**Figure 8.**Pulse (solid blue, left axis) response of a first-order material delay (dashed red, right axis) and a third-order material delay (dotted green, right axis). Note the most material exits from the first-order delay in the first instant, i.e., there is only a DT delay.

**Figure 13.**Change in total cases when the population is 10% less careful with masks and social distancing.

**Table 1.**Value of total cases and deaths at the end of the simulation (5 July) for each of the five policies, as well as the percent change from the base case (no policy).

Policy | Total Cases (Millions) | % Change Total Cases | Deaths (Thousands) | % Change Deaths |
---|---|---|---|---|

Base case | 34.1 | 615 | ||

1. No behavior feedback | 16.4 | −51.9 | 333 | −45.9 |

2. People less careful | 42.1 | 23.5 | 817 | 32.8 |

3. Remove masks early | 34.5 | 1.17 | 620 | 0.813 |

4. Delayed vaccine | 37.0 | −8.50 | 653 | 6.18 |

5. Vaccinate youth | 34.0 | −0.293 | 614 | −0.163 |

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