How Much Evidence is Enough? The FDA’s Conflicting Positions on Vaccines and Devices
David Simon, PhD, JD, LLM — Associate Professor of Law, Northeastern University School of Law.
Michael K. Paasche-Orlow, MD, MA, MPH — Department of Medicine, Tufts University School of Medicine, Tufts Medical Center, Boston, MA.
Hooman Noorchashm, MD, PhD — Research Professor, Northeastern University School of Law.
All three are Co-Directors of the Amy J. Reed Collaborative on Device Safety.
The FDA has recently announced it intends to “remove a key limitation on the use of real-world evidence (RWE) in” its device review and authorization process, signaling looser standard of device review with more RWE. At the same time, it has claimed that the evidence supporting vaccines is too weak and needs further study. In this article, we compare the evidence supporting vaccines to that supporting device approvals. We argue that the FDA’s position is inconsistent and, if it is serious about patient safety and product effectiveness, it will reexamine its posture toward devices.
Evidence, Authorization, and Trust
Patients and providers assume that the FDA authorizes medical products for use based on clinical evidence demonstrating their safety and efficacy/effectiveness. When the FDA authorizes products without this evidence, it can undermine public trust, compromising its ability to protect public health. One area where public trust has faltered is vaccines. Given the importance of public trust, it is reasonable to scrutinize the scientific rigor of vaccine trials—to ensure that side-effects and efficacy are measured with care, and to establish transparent processes and access to data.
This evidence-based approach, however, cannot be reserved exclusively for vaccines. It must be applied across all medical products, including medical devices. And while the FDA can require evidence proportional to the level of risk posed by the product, the FDA should not apply lower standards to certain industries arbitrarily or without sufficient justification. Doing so will create the appearance of special favors, shield certain industry from scrutiny, and expose patients and providers to undue risk—undermining the legitimacy of the FDA. A trusted regulatory process is a consistent, fair one, in which regulators evaluate all products under the same general standards. Proof of safety and efficacy cannot be required of vaccines but then be ignored for other products like medical devices.
Vaccines
Vaccines have significant evidentiary support in both basic immunology and epidemiology. They mimic natural infection, eliciting humoral and cellular responses—including neutralizing antibodies and memory T and B cells—without causing disease. This establishes long-term immunologic memory for rapid response upon re-exposure.1
Vaccines undergo rigorous pre-licensure testing, typically in large Phase III randomized, double-blind, placebo-controlled trials assessing safety and efficacy.2 Ethical constraints sometimes require active controls (e.g., existing vaccines) in non-inferiority designs for diseases with proven prevention.
Efficacy measurement faces challenges: evolving pathogens (e.g., variants in COVID-19 or influenza), low incidence reducing statistical power, waning immunity, and differences between trial and real-world settings.3 These factors have contributed to debates over variable effectiveness in COVID-19 vaccines, preventive impacts of influenza vaccines, and ethical issues in trials for established vaccines like hepatitis B, amid rising hesitancy and misinformation.
Nevertheless, the core principle holds: vaccines induce memory responses (antibodies and T cells) that protect against infection or mitigate severity. Decades of post-licensure data from billions of doses worldwide affirm robust safety profiles, with adverse events monitored via systems like Vaccine Adverse Event Reporting System. Long-term studies highlight vaccines’ success in preventing diseases (e.g., measles, polio, pertussis) and delivering public health gains through herd immunity and eradication. Diligence for patient safety and efficacy is welcome, but care is needed to prevent avoidable disease outbreaks.
Devices
In comparison, the evidence supporting device authorization is exceedingly weak. Nearly 99 percent of all FDA-authorized devices are moderate- to low-risk, the vast majority of which (conservatively 85-90 percent) are not supported by any evidence from clinical trials.45 Higher risk devices—e.g., implantable devices that sustain life, like pacemakers—typically require clinical evidence, but such research typically lacks scientific rigor.6 Trials are often small, unblinded, and are not randomized.6 Despite the low threshold for evidence in devices, in 2017 the FDA issued guidance on how it would use RWE in device authorizations. Final guidance published on December 19, 2025, combined with its recent statements, show that the FDA appears more willing than ever to forgo the kind of clinical evidence needed to ensure devices are safe and effective for their intended uses.
At the same time, postmarket surveillance for devices is also weak. Although companies must report adverse events to the FDA, only a small fraction (1%) are thought to be reported. And when data is reported, it is often distorted in different ways, making it difficult to understand what safety events were about or whether the device caused the injury. Yet, thousands of devices reach the market every year, and some—likely only a fraction of unsafe devices—are recalled for safety issues. Despite this, FDA almost never pulls them from the market. Those injured may be able to file lawsuits, but a large percentage of harms are non-recoverable because damages are too small, causation is too difficult to prove, or manufacturers are protected by law from liability.
Comparing the Evidence: Vaccines v. Devices
There are a limited number of vaccines. Over decades, scientists and researchers have published and presented reams of safety and efficacy data supporting them. There are known risks, and some unknown risks. Although the safety and efficacy profile is strong for many vaccines, there are opportunities to continue to improve the quality of vaccine research and to earn public trust in the process. One potential place for reform is the Vaccine Injury Compensation Fund (VICF), which provides some legal redress for those injured by them. Policymakers should explore how to improve its funding and operations. At the same time, policymakers should recognize that vaccines are based on decades of research and produce immense gains in social welfare by preventing serious diseases at low cost. Even when factoring in adverse events and payments in the VICF, the gains are significant. Vaccines remain robust and useful tools in the public health toolkit.
Devices, by contrast, are numerous — thousands are authorized every year. They have a rather checkered safety and efficacy history. Vaginal mesh, hip implants, breast implants, and morcellators all have caused serious damage to patients, some of whom cannot recover because of certain legal doctrines that inoculate manufacturers from liability. And while devices do improve social welfare, their effect on social welfare is much smaller, and more equivocal, than vaccines.
While RWE can be useful, the FDA has not explained a coherent policy for using it. Instead, it has inverted the appropriate standards: where there is overwhelming of RWE evidence, it does not count; but where there is little to no RWE evidence, it is highly valued. This analytical inconsistency undermines public trust in the FDA and jeopardizes the safety and well-being of American patients. Indeed, the safety and efficacy of medical devices should be based on a foundation of more, not less scientific rigor—rigor that will be lost if the FDA pursues RWE without shoring up pre-authorization requirements.
References
- Sallusto F, Lanzavecchia A, Araki K, Ahmed R. From vaccines to memory and back. Immunity. 2010;33(4):451-463. doi:10.1016/j.immuni.2010.10.008
- Orenstein WA, Offit PA, Edwards KM, Plotkin SA. Plotkin’s Vaccines, E-Book. Elsevier Health Sciences; 2022.
- McLean HQ, Belongia EA. Influenza Vaccine Effectiveness: New Insights and Challenges. Cold Spring Harb Perspect Med. 2021;11(6):a038315. doi:10.1101/cshperspect.a038315
- Shah P, Olavarria O, Dhanani N, et al. The Food and Drug Administration’s (FDA’s) 510(k) Process: A Systematic Review of 1000 Cases. Am J Med. 2023;136(2):172-178.e14. doi:10.1016/j.amjmed.2022.09.006
- Medical Devices and the Public’s Health: The FDA 510(k) Clearance Process at 35 Years. National Academies Press; 2011:13150. doi:10.17226/13150
- Dhruva SS, Bero LA, Redberg RF. Strength of Study Evidence Examined by the FDA in Premarket Approval of Cardiovascular Devices. JAMA. 2009;302(24):2679-2685. doi:10.1001/jama.2009.1899
Acknowledgments. All three authors receive funding from Arnold Ventures. MPO receives funding from the National Institutes of Health. Conflicts. DAS owns and operates Simon Law Group LLC.