I am curious about what actually goes into a vaccine placebo formulation, given that there were apparently some reactions reported by trial subjects who received the Pfizer SARS-CoV-2 placebo.
From what I've been able to find out online, the actual vaccine contains as principle ingredients (simplified):
- mRNA (active ingredient) to make the target antigen (spike protein)
- lipids (to protect the mRNA and facilitate its delivery into cells)
- salt(s) to adjust pH and match the salinity of blood
- sugar to address issues which occur when the vaccine is frozen
An injectable placebo could be as simple as a saline solution... if so, how could reactions be explained? Is it entirely psychosomatic? Is the Pfizer SARS-CoV-2 trial placebo the complete formulation (or some subset of vaccine components) minus the active (mRNA) ingredient?
The lipids have been implicated in allergic reactions to the actual vaccine; would they have been present in the placebo and account for the placebo reactions?