VAERS warns researchers using its database that the data should not be used in isolation to draw conclusions about cause and effect. Nonetheless, raw data from VAERS has been used in vaccine litigation to support the claim that vaccines cause autism. Litigation related to vaccines and autism has led to an increase in VAERS reports filed by plaintiff's attorneys. A 2006 article in Pediatrics found that most VAERS reports related to thimerosal, and many related to autism, were filed in connection with litigation, leading the authors to caution that inappropriate reliance on VAERS data may be a source of bias. The study's lead author stated: "Lawyers are manipulating this system to show increases [in vaccine-related adverse events] that are based on litigation, not health research." Paul Offit, chief of infectious disease at Children's Hospital of Philadelphia, wrote: Public health officials were disappointed to learn that reports of autism to VAERS weren't coming from parents, doctors, nurses, or nurse practitioners; they were coming from personal-injury lawyers ... For the lawyers, VAERS reports hadn't been a self-fulfilling prophecy; they'd been a self-generated prophecy. Limitations and abuse Like other spontaneous reporting systems, VAERS has several limitations, including underreporting, unverified reports, inconsistent data quality, and inadequate data about the number of people vaccinated. Due to the program's open and accessible design and its allowance of unverified reports, incomplete VAERS data is often used in false claims regarding vaccine safety. The Centers for Disease Control and Prevention (CDC) has warned that raw data from VAERS is not enough to determine whether a vaccine can cause a particular adverse event. For instance, Jim Laidler once reported to VAERS that a vaccine had turned him into The Incredible Hulk. The report was accepted and entered into the database, but the dubious nature of the report prompted a VAERS representative to contact Mr. Laidler, who then gave his consent to delete it from the database. During the COVID-19 pandemic, raw VAERS data has often been disseminated by anti-vaccine groups in order to justify inaccurate safety claims related to COVID-19 vaccines, including adverse reactions and alleged fatalities claimed to have been caused by vaccines. Websites such as Medalerts (published by the anti-vaccine group National Vaccine Information Center) and OpenVAERS (which published a tally of vaccine adverse events and fatalities allegedly linked to COVID-19 vaccines based on VAERS data), have been linked to this misinformation. Comparative studies of VAERS, which