Over the past few years, few topics have generated as much discussion, debate, and misinformation as COVID-19 vaccines. As billions of doses were administered worldwide, vaccines became central to the global effort to control the pandemic. Alongside the success of vaccination campaigns, however, a large number of viral claims began circulating online—many of them presenting alarming headlines about vaccine safety.

One claim that continues to appear in social media posts and sensational articles is that Pfizer has “admitted” its COVID-19 vaccines cause serious medical conditions. These posts often end abruptly with phrases such as “Pfizer admits its COVID vaccines cause a ca…” or similar wording designed to spark curiosity and concern.

But what does the evidence actually show?

In this article, we’ll examine the origins of these claims, what the scientific data says about vaccine safety, and why misleading headlines about major pharmaceutical companies spread so easily online.

The Global Vaccination Campaign

When COVID-19 spread around the world in early 2020, scientists and pharmaceutical companies raced to develop vaccines capable of preventing severe illness and death.

One of the first vaccines authorized for emergency use was developed by Pfizer in partnership with BioNTech. The vaccine, known as Pfizer-BioNTech COVID-19 vaccine, uses messenger RNA (mRNA) technology to teach the body’s immune system how to recognize and fight the virus.

Regulators such as the U.S. Food and Drug Administration and the European Medicines Agency authorized the vaccine after large clinical trials showed it was highly effective at preventing severe disease.

Since its introduction, billions of doses have been administered worldwide.