Are vaccines placebo tested?

Saline-placebo-controlled trials are conducted for many vaccines to assess both safety and efficacy for a number of vaccines, including Rubella, Pneumococcal disease, Hib, HPV, Polio (The Salk version), Measles, Tdap, and COVID.

Sometimes a new vaccine is tested against an existing vaccine, or a placebo may contain an adjuvant, buffers, or stabilizers with a known safety record.

The World Health Organization guides the ethical use of placebos in vaccine trials in certain situations. It is acceptable when no effective vaccine is available and the new vaccine is intended to benefit the population being studied.

However, using placebos is considered unacceptable when there is already an effective and safe vaccine accessible in the public health system of the country where the trial is planned. In such cases, it would be unethical to withhold the existing vaccine from participants if not receiving it would pose a significant risk to their health.

Furthermore, the CDC’s definition of placebo is consistent with the accepted scientific understanding of placebos in vaccine trials. Inert placebos, such as saline solution, are commonly used, but in some cases, an active control, such as another vaccine, may be used to protect the health of participants.

It may be difficult to convince an ardently anti-vaccine person of the value of non-saline placebos because they enter the conversation already believing that vaccines writ large are dangerous.