Vaccine Side Effects: Correlation is Not Causation

Public-health officials must strike a “delicate balance” when communicating risks of side effects following vaccination. An adverse event would be directly linked to a vaccine using a specific lab test in ideal situations.

But these kinds of tests aren’t possible for most adverse events, either because there aren’t specific biomarkers to test for or because such tests are impractical, reported the journal Nature on April 1, 2021.

At least initially, the events are only linked by their timing: a person receives a vaccine and then experiences the side effect at some point afterward. This makes it particularly challenging to prove whether the vaccine actually caused the adverse event.

To address this issue, the US government launched in 1990 the Vaccine Adverse Event Reporting System (VAERS) is a national early warning system to detect possible safety problems in U.S.-licensed vaccines. VAERS accepts and analyzes reports of adverse events (possible side effects) after a person has received a vaccination. Anyone can report an adverse event to VAERS. 

An important note from the U.S. HHS says, 'If you are experiencing a medical emergency, seek immediate assistance from a healthcare provider or call 9-1-1. The U.S. CDC and FDA do not provide individual medical treatment, advice, or diagnosis. If you need individual medical or health care advice, consult a qualified healthcare provider.'