Aren't vaccines never tested against a real placebo?
Here is what the checked sources say. Each title links to the original.
Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine
An example of a large placebo-controlled trial, run by the vaccine's makers, Pfizer and BioNTech, as licensing trials are. 43,448 people aged 16 and up were randomly given two doses of either the vaccine (21,720) or a saline placebo (21,728), without knowing which. There were 8 lab-confirmed COVID-19 cases starting at least 7 days after dose two in the vaccine group versus 162 with placebo, 95% efficacy. Over a median 2 months of safety follow-up, side effects were mostly short-term arm pain, tiredness and headache; serious adverse events were low and similar in both groups.
Fact Checked: Childhood Vaccines Are Carefully Studied—Including with Placebos—to Ensure They're Safe and Effective
The American Academy of Pediatrics explains how controls are chosen in childhood vaccine trials. When no vaccine yet exists for a disease, the control group may get saline or another substance known to be safe. When a new vaccine would replace an older one, the control group usually gets the older, already-tested vaccine, because leaving children unprotected against a disease that already has a vaccine is considered unethical. AAP notes that in 1950s polio trials some children in the placebo group got polio and died, and says ethical standards have since evolved.
The Persistent Misleading Claim That Vaccines Aren't Properly Tested for Safety
FactCheck.org (April 2026) says those demanding a true placebo often accept only saline or another inert substance, and do not count controls that contain a vaccine's inactive ingredients but not its active part. Many trials used such controls, including the 1954 polio trial, chickenpox and both rotavirus vaccines. One ethics review judged four saline doses for so many infants unethical, so the 37,000-child pneumococcal trial used a comparison vaccine. Researchers note trials are unlikely to be large enough to rule out very rare side effects, so monitoring continues after approval.