The Gardasil lawsuit is a large-scale legal action against Merck, the manufacturer of the HPV vaccine, in which plaintiffs claim the vaccine caused serious autoimmune and neurological injuries that Merck failed to adequately warn about. As of January 2026, 258 cases are consolidated in a federal Multidistrict Litigation (MDL 3036) in the Western District of North Carolina. The litigation has faced a major setback for plaintiffs: in March 2025, the presiding judge ruled in Merck’s favor on the central failure-to-warn claims.
What Plaintiffs Are Claiming
The lawsuits bring a mix of products liability, fraud, negligence, breach of warranty, and state consumer protection claims. At the core, plaintiffs argue two things: that Gardasil caused them serious health problems, and that Merck knew or should have known about these risks and failed to warn patients.
The specific conditions plaintiffs report developing after vaccination include postural orthostatic tachycardia syndrome (POTS), a disorder where the heart rate spikes abnormally upon standing, causing dizziness, fatigue, and fainting. Others cite complex regional pain syndrome (CRPS), a chronic pain condition, as well as premature ovarian failure, where ovarian function stops before age 40. The bellwether plaintiffs, who received Gardasil between 2012 and 2021, described experiencing excessive neurological and autoimmune symptoms they attribute to the vaccine.
The Clinical Trial Design Controversy
One of the most distinctive allegations in this litigation involves how Merck designed its original safety trials. Multiple pivotal trials of the quadrivalent HPV vaccine were described as “placebo-controlled,” but the control group didn’t receive a true inert placebo. Instead, participants in the control arm were injected with amorphous aluminum hydroxyphosphate sulfate (AAHS), a proprietary aluminum-based adjuvant that is also an active ingredient in the vaccine itself.
Plaintiffs argue this is a critical problem. If both the vaccine group and the “placebo” group received the same aluminum compound, and if that compound itself can trigger adverse reactions, the trial design would mask safety signals by making both groups look similar. A published analysis in BMJ Evidence-Based Medicine found that in one trial that used a control arm without AAHS, the absolute risk increase for adverse events was 25%, a much larger gap than seen in the AAHS-controlled trials.
The informed consent forms add another layer. Researchers reviewed the original consent documents and found that some trials gave participants no information about what was in the control injection. Others described it as an “inactive solution” or “a dose that contains no active ingredients,” which critics say was misleading given the control contained a pharmacologically active adjuvant. Merck has said the AAHS was included to preserve blinding and to isolate the safety profile of the virus-like particles in the vaccine, arguing the adjuvant’s safety was already well established.
The Alleged Biological Mechanisms
Plaintiffs’ legal filings rely on several scientific hypotheses to explain how the vaccine could cause harm. The first is molecular mimicry: the idea that antibodies generated against the HPV proteins in the vaccine could cross-react with similar-looking human proteins, essentially causing the immune system to attack the body’s own tissues. The second centers on the aluminum adjuvant itself, pointing to research suggesting aluminum hydroxide can cause a condition called macrophagic myofasciitis, with symptoms including cognitive dysfunction and central nervous system inflammation.
A third hypothesis involves polysorbate 80, an ingredient found in both aluminum-containing and non-aluminum HPV vaccines. One animal study found that newborn rats injected with polysorbate 80 experienced ovarian damage across all doses tested. Plaintiffs use this to support claims of premature ovarian failure.
These mechanisms remain heavily disputed. A 2022 paper in Cancer Science examined the specific studies cited in the lawsuits and noted that several of the aluminum-related findings involved a different type of aluminum compound than what Gardasil actually contains. The European Medicines Agency conducted its own review in 2015, concluding that the evidence did not support a causal link between HPV vaccination and POTS or CRPS, though that review itself was later criticized for methodological problems, including relying heavily on manufacturers’ own case assessments.
The March 2025 Ruling
The litigation reached a turning point in March 2025 when Judge Kenneth Bell ruled in Merck’s favor on the bellwether cases. The judge found that by 2013, the latest date plaintiffs argued new warnings were needed, Merck and the broader scientific community had only a “paucity” of evidence suggesting a causal connection between Gardasil and the alleged conditions. Because federal law governs vaccine labeling, and because the evidence at the time didn’t meet the threshold that would have given Merck authority to unilaterally add warnings, the judge ruled that federal law preempted the plaintiffs’ state-level failure-to-warn claims.
“Federal law requires more than speculative inferences prior to adding dire warnings to lifesaving vaccines that discourage their use,” Bell wrote in a 35-page decision. “That evidence is lacking here.” This ruling is significant because failure to warn was the central legal theory in most of the cases. Without it, plaintiffs lose their primary path to holding Merck liable.
What Regulators Say About Safety
The CDC’s position, based on more than 15 years of post-market surveillance and over 135 million doses distributed in the United States, is that HPV vaccines are safe and effective. Monitoring through the Vaccine Adverse Event Reporting System (VAERS) has found the most common side effects to be injection-site pain, redness, swelling, dizziness, fainting, nausea, and headache. With the exception of fainting, which is common among adolescents after any vaccination, no adverse events have been confirmed at higher-than-expected rates following HPV vaccination. Serious allergic reactions occur at a rate of roughly 3 cases per million doses.
Merck’s own position emphasizes that the vaccine’s dosing regimens were evaluated in large clinical studies meeting regulatory standards, and that HPV vaccination has demonstrated real-world reductions in certain HPV-related cervical cancers at the population level.
Where the Litigation Stands
The March 2025 ruling was a decisive win for Merck, but it does not necessarily end every case. Some plaintiffs may pursue appeals or attempt to proceed on claims other than failure to warn, such as fraud or manufacturing defect theories. The MDL still has 258 pending actions as of early 2026, though the practical viability of many of those cases is now uncertain given the bellwether outcome. For anyone who received Gardasil and is tracking this litigation, the key development is that the federal court found the scientific evidence insufficient to support the claim that Merck should have warned about the conditions plaintiffs describe.