Summary of Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. The consolidated balance sheet as of September 30, 2021, the consolidated statements of operations and the consolidated statements of comprehensive loss for the three and nine months ended September 30, 2021 and 2020, the consolidated statements of changes in stockholders’ equity for the three and nine months ended September 30, 2021 and 2020 and the consolidated statements of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited, but include all adjustments (consisting of normal recurring adjustments) that the Company considers necessary for a fair presentation of the financial position, operating results, comprehensive loss, changes in stockholders’ equity and cash flows, respectively, for the periods presented. Although the Company believes that the disclosures in these unaudited consolidated financial statements are adequate to make the information presented not misleading, certain information and footnote information normally included in consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted as permitted under the rules and regulations of the United States Securities and Exchange Commission (“SEC”). The unaudited consolidated financial statements include the accounts of Novavax, Inc. and its wholly owned subsidiaries, including Novavax AB and Novavax CZ. All intercompany accounts and transactions have been eliminated in consolidation. The accompanying unaudited consolidated financial statements are presented in U.S. dollars. The functional currency of Novavax AB, which is located in Sweden, is the local currency (Swedish Krona), and the functional currency of Novavax CZ, which is located in the Czech Republic, is the local currency (Czech Koruna). The translation of assets and liabilities of these subsidiaries to U.S. dollars is made at the exchange rate in effect at the consolidated balance sheet date, while equity accounts are translated at historical rates. The translation of the statement of operations data is made at the average exchange rate in effect for the period. The translation of operating cash flow data is made at the average exchange rate in effect for the period, and investing and financing cash flow data is translated at the exchange rate in effect at the date of the underlying transaction. Translation gains and losses are recognized as a component of accumulated other comprehensive income in the accompanying unaudited consolidated balance sheets. Accumulated other comprehensive income included a foreign currency translation balance of $0.9 million and $7.0 million as of September 30, 2021 and December 31, 2020, respectively. The accompanying unaudited consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020. Results for this or any interim period are not necessarily indicative of results for any future interim period or for the entire year. The Company operates in one business segment.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from those estimates.
Cash and Cash Equivalents	Cash equivalents are recorded at cost, which approximate fair value due to their short-term nature.
Marketable Securities	Marketable Securities The Company invests in marketable securities that generally consist of debt securities with maturities greater than three months from the date of purchase that include commercial paper, government-backed securities, treasury securities, corporate notes and agency securities. Classification of marketable securities between current and non-current is dependent upon the maturity date at the balance sheet date taking into consideration the Company's ability and intent to hold the investment to maturity. Interest and dividend income are recorded when earned and included in investment income in the consolidated statements of operations. Premiums and discounts, if any, on marketable securities are amortized or accreted to maturity and included in investment income in the consolidated statements of operations. The specific identification method is used in computing realized gains and losses on the sale of the Company's securities. The Company classifies its marketable securities with readily determinable fair values as “available-for-sale.” Investments in securities that are classified as available-for-sale are measured at fair market value in the consolidated balance sheets, and unrealized gains and losses on marketable securities are reported as a separate component of stockholders' equity until realized. Marketable securities are evaluated periodically to determine whether a decline in value is “other-than-temporary.” The term “other-than-temporary” is not intended to indicate a permanent decline in value. Rather, it means that the prospects for a near-term recovery of value are not necessarily favorable, or that there is a lack of evidence to support fair values equal to, or greater than, the carrying value of the security. Management reviews criteria, such as the magnitude and duration of the decline, as well as the Company's ability to hold the securities, including whether the Company will be required to sell a security prior to recovery of its amortized cost basis, the investment issuer's financial condition and business outlook to predict whether the loss in value is other-than-temporary. Realized gains and losses and declines in value determined to be other-than-temporary are recorded as other income (expense) in the consolidated statements of operations.
Restricted Cash	Restricted Cash The Company’s current and non-current restricted cash includes payments received under the Coalition for Epidemic Preparedness Innovations (“CEPI”) funding agreements, payments received under the Bill & Melinda Gates Foundation (“BMGF”) grant agreements and cash collateral accounts under letters of credit that serve as security deposits for certain facility leases. The Company will utilize the CEPI and BMGF funds as it incurs expenses for services performed under these agreements.
Pre-Launch Inventory	Pre-Launch InventoryPrior to an emergency use authorization ("EUA") or regulatory approval of NVX-CoV2373, the Company's policy is to recognize the cost associated with acquiring raw materials and production for preclinical studies, clinical trials and pre-launch inventory, including both internal manufacturing and third-party Contract Manufacturing Organizations ("CMO"), as research and development expense in its consolidated statements of operations, in the period in which the costs are incurred. When the Company believes EUA or regulatory approval and subsequent commercialization of NVX-CoV2373 is probable, and expects future economic benefit from the sales of NVX-CoV2373 to be realized, the Company will then start capitalizing the costs of production as inventory.
Revenue Recognition	Revenue Recognition The Company has various arrangements that include a right for a third party to use the Company's intellectual property as a functional license. These licensing arrangements include sales-based royalties, as well as certain development and commercial milestone payments, and the license is deemed to be the predominant item to which the sales-based royalties or milestone payments relate. For arrangements that include a development or regulatory milestone payment, the Company evaluates whether the associated event is considered probable of achievement and estimates the amount to be included in the transaction price using the most likely amount method. Milestone payments that are not within the Company or licensee's control, such as those dependent upon receipt of regulatory approval, are not considered probable of achievement until the triggering event occurs. At the end of each reporting period, the Company reevaluates the probability of achievement of each milestone and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis and affect revenue and results of operations in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based upon the achievement of a certain level of product sales, wherein the license is deemed to be the sole or predominant item to which the payments relate, the Company recognizes revenue on the satisfaction (or partial satisfaction) of its performance obligation to which some or all of the payment has been allocated, which is normally on the occurrence of the related sales. As a practical expedient, the Company has elected not to disclose the aggregate amount of the transaction price for the variable consideration that represents sales-based royalties under the licensing arrangements. Consideration for optional goods and/or services is excluded from the transaction price at contract inception.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with ASC Topic 740, Income Taxes. Under the liability method, deferred income taxes are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis and operating loss carryforwards. The Company has historically generated significant federal, state and foreign tax net operating losses, which may be subject to limitation in future periods. Management has fully reserved the related deferred tax assets with a valuation allowance in the current reporting period as more likely than not the related benefit will not be realized. The Company is currently subject to examination in all open tax years.
Net Loss per Share	Net Loss per Share Net loss per share is computed using the weighted average number of shares of common stock outstanding. As of September 30, 2021 and 2020, the Company had outstanding stock options, stock appreciation rights (“SARs”) and unvested restricted stock units (“RSUs”) totaling 4,911,656 and 6,623,466, respectively. As of September 30, 2021, the Company’s Notes (see Note 7) would have been convertible into approximately 2,385,800 shares of the Company’s common stock assuming a common stock price of $136.20 or higher. These shares, after giving effect to the add back of interest expense and unamortized debt issuance costs on the Notes and any shares due to the Company upon settlement of its capped call transactions, are excluded from the computation, as their effect is antidilutive.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Not Yet Adopted In August 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (“ASU 2020-06”), which will simplify the accounting for certain financial instruments with characteristics of liabilities and equity, including certain convertible instruments and contracts in an entity’s own equity. Specifically, the new standard will remove the separation models required for convertible debt with cash conversion features and convertible instruments with beneficial conversion features. It will also remove certain settlement conditions that are currently required for equity contracts to qualify for the derivative scope exception and will simplify the diluted earnings per share calculation for convertible instruments. ASU 2020-06 will be effective January 1, 2022 for the Company and may be applied using a full or modified retrospective approach. Management has evaluated the impact of adopting ASU 2020-06 and has determined that it will not have a material impact on the Company’s consolidated financial statements.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2021

The accompanying unaudited consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. The consolidated balance sheet as of September 30, 2021, the consolidated statements of operations and the consolidated statements of comprehensive loss for the three and nine months ended September 30, 2021 and 2020, the consolidated statements of changes in stockholders’ equity for the three and nine months ended September 30, 2021 and 2020 and the consolidated statements of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited, but include all adjustments (consisting of normal recurring adjustments) that the Company considers necessary for a fair presentation of the financial position, operating results, comprehensive loss, changes in stockholders’ equity and cash flows, respectively, for the periods presented. Although the Company believes that the disclosures in these unaudited consolidated financial statements are adequate to make the information presented not misleading, certain information and footnote information normally included in consolidated financial statements prepared in accordance with U.S. GAAP have been condensed or omitted as permitted under the rules and regulations of the United States Securities and Exchange Commission (“SEC”).

The unaudited consolidated financial statements include the accounts of Novavax, Inc. and its wholly owned subsidiaries, including Novavax AB and Novavax CZ. All intercompany accounts and transactions have been eliminated in consolidation.

The accompanying unaudited consolidated financial statements are presented in U.S. dollars. The functional currency of Novavax AB, which is located in Sweden, is the local currency (Swedish Krona), and the functional currency of Novavax CZ, which is located in the Czech Republic, is the local currency (Czech Koruna). The translation of assets and liabilities of these subsidiaries to U.S. dollars is made at the exchange rate in effect at the consolidated balance sheet date, while equity accounts are translated at historical rates. The translation of the statement of operations data is made at the average exchange rate in effect for the period. The translation of operating cash flow data is made at the average exchange rate in effect for the period, and investing and financing cash flow data is translated at the exchange rate in effect at the date of the underlying transaction. Translation gains and losses are recognized as a component of accumulated other comprehensive income in the accompanying unaudited consolidated balance sheets. Accumulated other comprehensive income included a foreign currency translation balance of $0.9 million and $7.0 million as of September 30, 2021 and December 31, 2020, respectively.

The accompanying unaudited consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020. Results for this or any interim period are not necessarily indicative of results for any future interim period or for the entire year. The Company operates in one business segment.

Use of Estimates

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from those estimates.

Cash and Cash Equivalents

Cash equivalents are recorded at cost, which approximate fair value due to their short-term nature.

Marketable Securities

The Company invests in marketable securities that generally consist of debt securities with maturities greater than three months from the date of purchase that include commercial paper, government-backed securities, treasury securities, corporate notes and agency securities. Classification of marketable securities between current and non-current is dependent upon the maturity date at the balance sheet date taking into consideration the Company's ability and intent to hold the investment to maturity.

Interest and dividend income are recorded when earned and included in investment income in the consolidated statements of operations. Premiums and discounts, if any, on marketable securities are amortized or accreted to maturity and included in investment income in the consolidated statements of operations. The specific identification method is used in computing realized gains and losses on the sale of the Company's securities.

The Company classifies its marketable securities with readily determinable fair values as “available-for-sale.” Investments in securities that are classified as available-for-sale are measured at fair market value in the consolidated balance sheets, and unrealized gains and losses on marketable securities are reported as a separate component of stockholders' equity until realized. Marketable securities are evaluated periodically to determine whether a decline in value is “other-than-temporary.” The term “other-than-temporary” is not intended to indicate a permanent decline in value. Rather, it means that the prospects for a near-term recovery of value are not necessarily favorable, or that there is a lack of evidence to support fair values equal to, or greater than, the carrying value of the security. Management reviews criteria, such as the magnitude and duration of the decline, as well as the Company's ability to hold the securities, including whether the Company will be required to sell a security prior to recovery of its amortized cost basis, the investment issuer's financial condition and business outlook to predict whether the loss in value is other-than-temporary. Realized gains and losses and declines in value determined to be other-than-temporary are recorded as other income (expense) in the consolidated statements of operations.

Restricted Cash

The Company’s current and non-current restricted cash includes payments received under the Coalition for Epidemic Preparedness Innovations (“CEPI”) funding agreements, payments received under the Bill & Melinda Gates Foundation (“BMGF”) grant agreements and cash collateral accounts under letters of credit that serve as security deposits for certain facility leases. The Company will utilize the CEPI and BMGF funds as it incurs expenses for services performed under these agreements.

Pre-Launch Inventory

Pre-Launch InventoryPrior to an emergency use authorization ("EUA") or regulatory approval of NVX-CoV2373, the Company's policy is to recognize the cost associated with acquiring raw materials and production for preclinical studies, clinical trials and pre-launch inventory, including both internal manufacturing and third-party Contract Manufacturing Organizations ("CMO"), as research and development expense in its consolidated statements of operations, in the period in which the costs are incurred. When the Company believes EUA or regulatory approval and subsequent commercialization of NVX-CoV2373 is probable, and expects future economic benefit from the sales of NVX-CoV2373 to be realized, the Company will then start capitalizing the costs of production as inventory.

Revenue Recognition

Revenue Recognition The Company has various arrangements that include a right for a third party to use the Company's intellectual property as a functional license. These licensing arrangements include sales-based royalties, as well as certain development and commercial milestone payments, and the license is deemed to be the predominant item to which the sales-based royalties or milestone payments relate. For arrangements that include a development or regulatory milestone payment, the Company evaluates whether the associated event is considered probable of achievement and estimates the amount to be included in the transaction price using the most likely amount method. Milestone payments that are not within the Company or licensee's control, such as those dependent upon receipt of regulatory approval, are not considered probable of achievement until the triggering event occurs. At the end of each reporting period, the Company reevaluates the probability of achievement of each milestone and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis and affect revenue and results of operations in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based upon the achievement of a certain level of product sales, wherein the license is deemed to be the sole or predominant item to which the payments relate, the Company recognizes revenue on the satisfaction (or partial satisfaction) of its performance obligation to which some or all of the payment has been allocated, which is normally on the occurrence of the related sales. As a practical expedient, the Company has elected not to disclose the aggregate amount of the transaction price for the variable consideration that represents sales-based royalties under the licensing arrangements. Consideration for optional goods and/or services is excluded from the transaction price at contract inception.

Income Taxes

The Company accounts for income taxes in accordance with ASC Topic 740, Income Taxes. Under the liability method, deferred income taxes are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis and operating loss carryforwards.

The Company has historically generated significant federal, state and foreign tax net operating losses, which may be subject to limitation in future periods. Management has fully reserved the related deferred tax assets with a valuation allowance in the current reporting period as more likely than not the related benefit will not be realized. The Company is currently subject to examination in all open tax years.

Net Loss per Share

Net loss per share is computed using the weighted average number of shares of common stock outstanding. As of September 30, 2021 and 2020, the Company had outstanding stock options, stock appreciation rights (“SARs”) and unvested restricted stock units (“RSUs”) totaling 4,911,656 and 6,623,466, respectively.

As of September 30, 2021, the Company’s Notes (see Note 7) would have been convertible into approximately 2,385,800 shares of the Company’s common stock assuming a common stock price of $136.20 or higher. These shares, after giving effect to the add back of interest expense and unamortized debt issuance costs on the Notes and any shares due to the Company upon settlement of its capped call transactions, are excluded from the computation, as their effect is antidilutive.

Recent Accounting Pronouncements

Not Yet Adopted

In August 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (“ASU 2020-06”), which will simplify the accounting for certain financial instruments with characteristics of liabilities and equity, including certain convertible instruments and contracts in an entity’s own equity. Specifically, the new standard will remove the separation models required for convertible debt with cash conversion features and convertible instruments with beneficial conversion features. It will also remove certain settlement conditions that are currently required for equity contracts to qualify for the derivative scope exception and will simplify the diluted earnings per share calculation for convertible instruments. ASU 2020-06 will be effective January 1, 2022 for the Company and may be applied using a full or modified retrospective approach. Management has evaluated the impact of adopting ASU 2020-06 and has determined that it will not have a material impact on the Company’s consolidated financial statements.