I read with interest your news story ‘Researchers find metal impurities in vaccines, but European regulator challenges study’ (
The Pharmaceutical Journal 2017;298:76).
Manufacturers have an interest and an obligation to produce all drugs, including vaccines, as contaminant free as possible. However, no process is completely contaminant free.
In the referenced study, the investigators use a technique that is far more sensitive than those typically used in drug manufacturing. Thus, it is not surprising that they detected contamination. The study is limited to analysis of a few manufactured vaccines and it is unclear whether their findings are unique to vaccines, or a more general outcome of drug manufacturing. The study also lacks critical controls for the procedures used in collection and analysis, which would allow the investigators to say conclusively that the contaminants originated from the vaccines, and not the environment. This leaves some uncertainty about the validity of the findings.
I agree with the European Medicines Agency (EMA) that it is unclear whether these contaminants, if they are, in fact, present, have any effect on human health. It is unknown if exposure to the levels of the contaminants detected in this study during normal vaccination would pose a greater risk than trace exposures acquired from the environment.
This one study, while interesting, is too premature to question the safety of vaccines. However, in light of the findings, manufacturers should evaluate their quality control methods for vaccines, and other drugs, to determine whether more sensitive methods should be used that can detect micro and nano contaminants. For now, the EMA was right to criticise the study and reaffirm the safety of vaccines.
Associate professor of microbiology and immunology
College of veterinary medicine
Cornell University, United States