The FDA is reportedly considering a boxed "black box" warning for COVID-19 vaccines, a move sources say is being led by Dr. Vinay Prasad of CBER. The proposal has not been finalized and no supporting data has been publicly released, prompting demands from experts and former FDA officials for transparent review. Manufacturers reiterate ongoing global safety monitoring while studies underscore the vaccines' substantial benefits. Public-health experts urge the FDA to publish evidence and convene independent review before taking such a major action.
FDA Reportedly Preparing 'Black Box' Warning for COVID-19 Vaccines — Experts Demand Transparency
One study estimated that in their first year of use, Covid-19 vaccinations averted almost 20 million deaths around the world. - Patrick T. Fallon/AFP/Getty Images/File
The U.S. Food and Drug Administration is reportedly preparing to add a boxed, or "black box," warning to COVID-19 vaccine prescribing information — the agency's most serious safety advisory. Two people familiar with the agency’s internal deliberations told reporters that Dr. Vinay Prasad, FDA chief medical and scientific officer and director of the Center for Biologics Evaluation and Research (CBER), is leading the effort. The plan has not been finalized and the FDA has not publicly released supporting data.
What a Boxed Warning Means
A boxed warning appears at the top of product labeling to flag risks that are life-threatening, disabling, or otherwise serious enough that clinicians must weigh them against benefits. Regulators also use boxed warnings to limit use to particular populations when that reduces risk. Past examples include opioid warnings about addiction and overdose, Accutane's warnings about birth defects, and ACAM2000's alerts for heart inflammation and encephalitis.
Scope, Timeline and Uncertainty
Sources say the agency could unveil any labeling updates by the end of the year, but it is unclear whether the warning — if issued — would apply only to mRNA vaccines (Pfizer and Moderna) or to all COVID-19 vaccines, or whether it would target particular age groups. HHS spokesperson Andrew Nixon cautioned that, "Unless the FDA announces it, any claim about what it will do is pure speculation."
Industry Statements and Evidence of Benefit
Moderna and Pfizer issued statements noting ongoing global safety monitoring and reaffirming the safety and efficacy profiles of their vaccines. Moderna highlighted that more than one billion doses of Spikevax have been distributed worldwide and that no new, undisclosed safety signals in children or pregnant women have emerged. Pfizer reiterated its support for its vaccine's safety record and declined additional comment.
Independent analyses and public health data emphasize the vaccines' benefits: one study estimated that COVID-19 vaccination averted nearly 20 million deaths worldwide in the first year of use. The Centers for Disease Control and Prevention reported that in the 2024–25 respiratory virus season, updated vaccines lowered emergency and urgent-care visits for children by about 76% (ages 9 months–4 years) and about 56% (ages 5–17), compared with unvaccinated peers.
In May, the FDA said it was requiring safety warnings in the prescribing information for the Covid-19 vaccines from Pfizer and Moderna. - Issam Ahmed/AFP/Getty Images
Claims, Safety Signals and the Call for Data
In a late-November memo to CBER staff, Dr. Prasad wrote that agency biostatistics and pharmacovigilance reviewers had "found that at least 10 children have died after and because of receiving COVID-19 vaccination." The memo offered no supporting data and prompted calls from outside experts for full disclosure of the evidence behind such claims. HHS said the FDA takes any death attributed to a regulated product seriously and that potential signals are under review.
The agency previously expanded safety language in May to include broader warnings about myocarditis and pericarditis — rare inflammatory heart events linked to mRNA vaccines — noting the observed risk was highest in males 12 through 24 years of age. Experts stress that myocarditis after vaccination has been rare, often self-limited, and that rates fell after dose-interval changes.
Reactions From Public Health Community
“Decisions of this magnitude require transparent, public review of the data,” said Dr. Aaron Kesselheim of Harvard, noting that boxed warnings are typically preceded by public notifications and advisory-panel reviews. “I have seen none of those usual steps in this case.”
A dozen former FDA commissioners published an open letter expressing concern about sweeping assertions regarding vaccine safety. Scientists and public-health officials have warned that issuing serious safety messaging without releasing the underlying evidence could undermine public confidence and reduce vaccine uptake, with negative consequences for population health.
“Very rare adverse events with vaccines can occur. But to discuss potential harms without releasing the data and without contextualizing the clear benefits is irresponsible,” said Dr. Fiona Havers, a former CDC epidemiologist.
What Comes Next
Officials say reviews are ongoing and that any decisions will be based on rigorous, independent evaluation of the data. Outside experts urge the FDA to: (1) publicly disclose the data and analyses prompting the potential action; (2) convene independent advisory committees to review evidence in an open forum; and (3) clearly communicate the balance of risks and benefits to clinicians and the public.
For now, the story centers on a high-stakes regulatory deliberation: whether to add the FDA's most serious label advisory to vaccines credited with preventing millions of deaths, and how that decision will be documented, justified and explained to the public.
