| Explanation of Responses: |
| (1) | The transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person. |
| (2) | Includes 1,250 shares acquired under the Issuer's Amended and Restated 2013 Employee Stock Purchase Plan, as amended, on January 31, 2021. |
| (3) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $271.60 to $272.50, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (4) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $273.17 to $274.14, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (5) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $274.18 to $275.02, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (6) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $275.32 to $276.31, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (7) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $276.64 to $277.63, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (8) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $278.38 to $279.28, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (9) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $279.8050 to $280.80, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (10) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $280.81 to $281.80, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (11) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $281.85 to $282.79, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (12) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $282.89 to $283.88, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (13) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $283.89 to $284.88, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (14) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $284.89 to $285.54, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (15) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $285.9150 to $286.70, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (16) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $287.19 to $287.53, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (17) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $288.79 to $288.81, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (18) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $289.87 to $289.96, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (19) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $291.00 to $291.94, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (20) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $296.36 to $296.74, inclusive. The reporting person undertakes to provide to Novavax, Inc., any security holder of Novavax, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each price within the range set forth in this footnote. |
| (21) | The reporting person received 2,434 shares of common stock upon the net exercise of 4,819 stock appreciation rights under the Novavax, Inc. Amended and Restated 2015 Stock Incentive Plan, as amended (the "Plan"). The reporting person forfeited 110 shares of common stock underlying the stock appreciation rights representing the base value and 2,275 shares of common stock underlying the stock appreciation rights to satisfy the withholding tax obligations resulting from the exercise, using the closing stock price on February 16, 2021 of $262.70. |
| (22) | Vesting of the shares subject to this option grant under the Plan were subject to the satisfaction of both (1) a time-based vesting requirement, pursuant to which twenty-five percent (25%) of the shares vested on the first anniversary of the November 14, 2016 grant date, and the remaining seventy-five percent (75%) of the shares vested in equal monthly installments on the first of each month over the following three (3) years, subject to continued employment through such vesting date, and (2) a performance-based vesting requirement, pursuant to which 33.33%, 33.33%, and 33.34% of the shares vested, if at any time during the four-year period from the November 14, 2016 grant date, the volume-weighted average stock price of Novavax, Inc.'s common stock met or exceeded $80.00, $120.00, or $160.00, respectively, for twenty (20) consecutive trading days. Novavax Inc.'s common stock did not meet $160.00 for twenty (20) consecutive trading days and therefore 2,918 shares were cancelled. |
| (23) | Twenty-five percent (25%) of the shares subject to this option grant under the Plan vested on the first anniversary of the December 15, 2017 grant date, and the remaining seventy-five percent (75%) of the shares vested or will vest in equal monthly installments over the following three (3) years subject to continued employment through such vesting date. |
| (24) | Twenty-five percent (25%) of the shares subject to this option grant under the Plan vested on the first anniversary of the December 13, 2018 grant date, and the remaining seventy-five percent (75%) of the shares vested or will vest in equal monthly installments over the following three (3) years subject to continued employment through such vesting date. |
| (25) | Twenty-five percent (25%) of the shares subject to this option grant under the Plan vested on the first anniversary of the September 26, 2019 grant date, and the remaining seventy-five percent (75%) of the shares vested or will vest in equal monthly installments over the following three (3) years subject to continued employment through such vesting date. |
| (26) | Twenty-five percent (25%) of the shares subject to this stock appreciation right grant under the Plan vested on the first anniversary of the September 26, 2019 grant date, and the remaining seventy-five percent (75%) of the shares will vest in equal monthly installments over the following three (3) years subject to continued employment through such vesting date. |