Vaccine Ingredients – Fetal Tissues

Varicella (chickenpox), rubella, hepatitis A, shingles and one preparation of rabies vaccine are all made in fetal embryo fibroblast cells. Fibroblast cells are the cells needed to hold skin and other connective tissue together. The fetal embryo fibroblast cells used to make vaccines were first obtained from elective termination of two pregnancies in the early 1960s. These same embryonic cells obtained from the early 1960s have continued to grow in the laboratory and are used to make vaccines today. No further sources of fetal cells are needed to make these vaccines.

The reasons that fetal cells were originally used included:

  • Viruses need cells to grow and tend to grow better in cells from humans than animals (because they infect humans).
  • Almost all cells die after they have divided a certain number of times; scientifically, this number is known as the Hayflick limit, and for most cell lines it is around 50 divisions; however, fetal cells can go through many more divisions before dying.

As scientists studied these viruses in the lab, they found that the best cells to use were the fetal cells mentioned above. When it was time to make a vaccine, they continued growing the viruses in the cells that worked best during these earlier studies.

Reference

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

Reviewed by Paul A. Offit, MD on November 06, 2014

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.