https://www.cdc.gov/vaccinesafety/ensuringsafety/monitoring/vaers/index.html

In bold: "As an early warning system, VAERS cannot prove that a vaccine caused a problem. Specifically, a report to VAERS does not mean that a vaccine caused an adverse event."

From the FAQs: One of the main limitations of VAERS data is that it cannot determine if the vaccine caused the reported adverse event. This limitation has caused confusion in the publicly available data from VAERS WONDER, specifically regarding the number of reported deaths. There have been instances where people have misinterpreted reports of deaths following vaccination as deaths caused by the vaccines; that is not accurate. VAERS accepts all reports of adverse health events following vaccinations without judging whether the vaccine caused the adverse health event. Some reports to VAERS represent true vaccine reactions and others are coincidental adverse health events and not related to vaccination. Overall, a causal relationship cannot be established using information from VAERS report alone.