Vaccine Ingredients – Human Proteins

Because human embryo cells are used to make a few vaccines, including the chickenpox, rubella, hepatitis A, one version of the rabies, and one version of the COVID-19 vaccines, people have asked whether proteins from these fetal cells are still present in the final vaccine preparations. The quantity of DNA in these vaccines is typically measured in picograms (trillionths of a gram).

Viruses are purified during vaccine production; therefore, it is unlikely that proteins from the human cells used to grow them would survive intact or in quantities sufficient to cause harm.


Offit PA and Moser CA. Vaccines and Your Child: Separating Fact from Fiction. 2011. Columbia University Press.

Reviewed by Paul A. Offit, MD on March 08, 2021

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.