A team of high school students from Centreville High School in Virginia, collaborating with the FDA, has uncovered concerning levels of DNA contamination in Pfizer’s experimental and commercial mRNA COVID-19 vaccines. Their findings, published on December 29th in the Journal of High School Science, have ignited discussions about vaccine manufacturing standards and quality control.
The student researchers—Tyler Wang, Alex Kim, and Kevin Kim—worked under FDA guidance at the White Oak Campus, developing an innovative method to detect replication-competent DNA impurities in vaccines.
This method involves isolating DNA from vaccine samples, circularizing it, and transforming it into Escherichia coli cells. The presence of antibiotic-resistant bacterial colonies after transformation signals replication-competent DNA, which should be absent or present only at minimal levels in vaccines.
The study analyzed two Pfizer vaccine lots, including monovalent and bivalent formulations. It revealed significant DNA contamination levels, with some samples exceeding the World Health Organization’s (WHO) recommended threshold by up to 470 times. Detected residual DNA ranged from 40 to 110 nanograms per dose. While no replication-competent DNA was found in Pfizer’s commercial batches, smaller DNA fragments—approximately 35 base pairs—were consistently identified.
Additionally, the study reported occasional replication-competent DNA in an in-house mRNA vaccine and a biosimilar vaccine, further underscoring the need for robust oversight in vaccine manufacturing.
These findings have raised questions about the processes used to ensure safety and purity in mRNA vaccine production and may prompt further scrutiny of manufacturing practices across the pharmaceutical industry.
Last month, a study published in the journal Science, Public Health Policy and the Law found that DNA contamination in Pfizer’s COVID-19 vaccines far exceeds legal limits by three to four times.
Researchers identified “large amounts of DNA after RNase A (Ribonuclease A) digestion in all lots with concentrations ranging from 32.7 ng to 43.4 ng per clinical dose.”
“This far exceeds the maximal acceptable concentration of 10 ng per clinical dose that has been set by international regulatory authorities,” they wrote.
“Of note, official limit values for residual DNA in biologicals are defined for antibodies, attenuated vaccines, and protein solutions, but not for RNA injections and – even more important – for nucleic acids packaged in transfection reagents like lipid nanoparticles, which were used for the first time in the COVID-19 injections,” the researchers stated in the study. “In fact, no scientific evidence exists that would permit a safety level of residual DNA to be defined in such injectables whatsoever.”