| Explanation of Responses: |
| (1) | The transaction was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person. |
| (2) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $189.27 to $190.03, inclusive. The reporting person undertakes to provide to Novavax, Inc. (the "Company"), any security holder of the Company, or the staff of the Securities and Exchange Commission (the "SEC"), upon request, full information regarding the number of shares sold at each price within the range set forth in this footnote. |
| (3) | The reported price is a weighted average price. These shares were sold in multiple transactions at prices ranging from $192.41 to $192.855, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $194.27 to $194.96, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $195.43 to $196.27, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $196.69 to $197.65, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $197.70 to $198.64, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $198.83 to $199.44, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $199.92 to $200.82, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $200.98 to $201.59, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $202.00 to $202.91, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $203.14 to $204.11, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $205.63 to $206.51, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $206.84 to $207.52, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $208.22 to $209.20, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $209.40 to $210.31, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold 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 $210.40 to $211.11, inclusive. The reporting person undertakes to provide to the Company, any security holder of the Company, or the staff of the SEC, upon request, full information regarding the number of shares sold at each price within the range set forth in this footnote. |
| (18) | On April 17, 2020, the reporting person was granted an option to purchase 165,000 shares of common stock of the Company pursuant to the Company's Amended and Restated 2015 Stock Incentive Plan, as amended. The vesting of the shares subject to this option grant is subject to the satisfaction of a performance-based vesting requirement, followed by time-based vesting. The performance metric required that the Company initiate a COVID-19 Phase 2 clinical trial within twelve (12) months of the grant date, which occurred when the Company initiated its Phase 2 clinical trial of NVX-CoV2373 in the U.S. on August 24, 2020. Following that event, fifty percent (50%) of the shares vested on August 24, 2021, the first anniversary of the initiation date, and the remaining fifty percent (50%) of the shares will vest on August 24, 2022, the second anniversary of the initiation date subject to continued employment through such vesting date. |