Company: DVAX
Filing Date: 2025-06-06
Form Type: DEFA14A
Source: 0001193125-25-136261
Chunk: 0

Company: DYNAVAX TECHNOLOGIES CORP
Filing Date: 2025-06-06
Form: DEFA14A
Chunk 0
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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box:

| ☐ | Preliminary Proxy Statement |

| ☐ | Confidential, for Use of the Commission Only (as permitted by Rule 
 14a-6(e)(2))                                                       |

| ☐ | Definitive Proxy Statement |

| ☒ | Definitive Additional Materials |

| ☐ | Soliciting Material Pursuant to §240.14a-12 |

Dynavax Technologies Corporation (Name of Registrant as Specified In Its Charter) (Name of Person(s) Filing Proxy Statement if other than the Registrant) Payment of Filing Fee (Check the appropriate box):

| ☒ | No fee required. |

| ☐ | Fee paid previously with preliminary materials. |

| ☐ | Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rule 
 14a-6(i)(1) and 0-11.                                                         |

On June 5, 2025, Dynavax Technologies Corporation (the “Company”) submitted the attached
statement in response to a report issued by Glass, Lewis & Co. on June 3, 2025, relating to the Company’s 2025 Annual Meeting of Stockholders.

June 5, 2025

Re: Dynavax
2025 Annual Meeting of Stockholders Glass Lewis Report

Dear Dynavax Stockholders,

We appreciate the opportunity to respond directly to the recent Glass Lewis Report regarding Dynavax’s upcoming Annual Meeting of Stockholders.

Glass Lewis’ report acknowledges that the Company’s 2019 strategic pivot toward vaccines has driven meaningful stockholder value creation, with a
203% total return over the last five years far outperforming peers and relevant indices. The report also recognizes the strength and depth of our Board, which has been significantly refreshed and
now includes directors with extensive, relevant expertise across vaccine development, commercialization and public company leadership. We firmly disagree with the report’s conclusion, as the individuals Glass Lewis recommends against, Brent
MacGregor and Scott Myers, have been instrumental to the success the report acknowledges and bring critical experience and leadership that are essential to Dynavax’s continued success and value creation.

Glass Lewis’ recommendation seems rooted in a liquidity analysis