史丹佛研究指出，罕见的新冠mRNA疫苗相关心肌炎源自快速两步骤免疫级联反应：先是巨噬细胞在接种辉瑞-BioNTech或莫德纳疫苗后释放发炎讯号，接著诱导T细胞分泌干扰素γ与趋化因子CXCL10，在少数人短暂伤害心肌。多数病例发生于青少年与年轻男性，在第二剂后一至三天出现胸痛、呼吸急促或心悸，通常以休息与支持性治疗即可痊愈，每十亿剂疫苗仅出现数千例，风险极低。

虽然心肌炎引起高度关注，但流行病学数据显示疫苗效益远大于风险。美国「曲速行动」投入超过一百亿美元，将开发压缩至约十一个月，创下史上最快疫苗上市纪录。到2022年底，约92%完整接种的美国人曾接种mRNA疫苗；模型估计，新冠疫苗在全球避免近两千万人死亡，其中美国超过一百万人，并预防数百万次住院与长期心血管、神经等后遗症。

同时，病例集中于年轻男性也推动政治反弹，包括美国卫生部取消22项总额近五亿美元的mRNA补助，以及食品药物管理局对成年死亡个案展开新调查。史丹佛团队在小鼠与人类心肌模型中发现，事先以具类雌激素作用的大豆异黄酮genistein处理，可抑制干扰素γ与CXCL10飙升并维持心功能，引发豆腐等含大豆食物可能温和减少此罕见发炎反应的联想。研究者强调，这项工作著重机转说明，疫苗对绝大多数人依然「非常非常安全」。

Stanford researchers report that rare post‑mRNA‑vaccine myocarditis stems from a rapid two‑step immune cascade in which macrophages release inflammatory proteins that trigger T cells to secrete interferon‑gamma and CXCL10, briefly injuring heart muscle in a small subset of mostly adolescent and young adult males. Symptoms such as chest pain typically appear one to three days after a second Pfizer‑BioNTech or Moderna dose and usually resolve with rest and supportive care. Overall incidence remains extremely low, at only a few thousand myocarditis cases per billion mRNA doses delivered worldwide.

Despite intense attention, epidemiologic data show that the vaccines’ benefits vastly outweigh these risks. Operation Warp Speed invested more than $10 billion to compress development to eleven months, enabling the fastest vaccine rollout in history. By late 2022, about 92% of fully vaccinated Americans had received an mRNA shot, and Covid vaccination is estimated to have prevented nearly 20 million deaths globally, including over one million in the United States, while averting millions of hospitalizations and long‑term complications.

At the same time, the clustering of cases in young men fueled political backlash, including cancellation of 22 US federal mRNA grants worth almost $500 million and fresh safety investigations by the Food and Drug Administration. The Stanford team also showed in mouse and human cardiac tissue models that pretreatment with genistein, a soy‑derived compound with estrogen‑like activity, can blunt interferon‑gamma surges and preserve heart function, prompting speculation that soy‑rich foods such as tofu might modestly temper this rare inflammatory response.