Are there really no vaccine studies done with a saline placebo? This is a common comment from antivaxers. They think vaccines cannot possibly be safe unless they are tested against an inert substance, aka the saline placebo, and there are none in existence. Therefore, vaccines are BAD.
What is a placebo and what is a saline placebo? A placebo is a harmless pill, medicine, or procedure prescribed more for the psychological benefit to the patient than for any physiological effect. Saline is something impregnated with salt. A saline placebo is basically a dose of salty water in lieu of a drug. So, the idea is that one group of study participants should get the vaccine while the other groups has a shot of salty water and neither group knows who got which. This is what is meant by double-blind, saline-placebo.
The World Health Organization has a great document explaining how placebos work and why certain substances are chosen for vaccine trials.
“Randomisation and the use of placebo interventions are designed to control for confounding effects, such that significant differences in disease incidence or adverse effects between the vaccine and control groups can likely be attributed to the vaccine. However, randomised, placebo-controlled trial designs often raise ethical concerns when participants in the control arm are deprived of an existing vaccine. Furthermore, testing a new vaccine against placebo is scientifically and ethically fraught when the hypothesis being tested is whether an experimental vaccine is more efficacious than one already in use in the same or in other settings.”
WHO goes on to detail how it may be unethical to deprive a study participant of a vaccine when an efficacious one exists. Meaning, if they are testing a new vaccine it would be unethical to test it against saline when an older, proven safe version exists. So, they can use the older version as the placebo and, therefore, not deprive the study participant of the protection. It is also considered ethical to use an adjuvant in lieu of a vaccine when the vaccine being studied has that adjuvant in it. So, you can use an aluminum adjuvant as a placebo if the adjuvant has been around enough to have been studied for safety. This is a controversial topic, with some feeling that aluminum adjuvants don’t have a proven safety record to use as a placebo. That is a topic for another blog post. This one is focused solely on saline placebo.
“Between these two poles, the use of placebo controls in vaccine trials may be justified even when an efficacious vaccine exists, provided the risk-benefit profile of the trial is acceptable. “
The rest of the document sets out a “framework sets out the conditions under which placebo use is clearly acceptable and clearly unacceptable in vaccine trials.”
That being said, this does not mean there are no vaccine studies which use a saline placebo. Many clinical trials use a saline placebo. Read inserts to learn more. And, PubMed, the online database of scientific studies organized by the USA’s National Institutes of Health, has many listings for vaccine studies which use a saline placebo.
Here are some vaccine studies which used saline placebo:
I could go on. This was from only the first two pages of my PubMed search.
So, as you can see, there are very important reasons why a scientist might not use a saline placebo in a vaccine study but there are also many vaccine studies which do use a saline placebo. As usual, antivaxers are conveying misinformation. In fact, my online friend, Mike, came up with this and I turned it into a meme. This is exactly what they do, goal shifting!
Remember to always verify claims!
This post is dedicated to Bernadette for always giving me great ideas for blog posts