Vaccine Ingredients – Fetal Cells

NOTE TO READERS: If a vaccine is not discussed on this page, it does not employ the use of fetal cells in production. For example, no influenza vaccine available in the U.S. requires the use of fetal cells for production.

Vaccines for varicella (chickenpox), rubella (the “R” in the MMR vaccine), hepatitis A, rabies (one version, called Imovax^®) and COVID-19 (one U.S.-approved version, Johnson & Johnson (J&J)/Janssen) are all made by growing the viruses in fetal cells. All of these, except the COVID-19 vaccine, are made using fibroblast cells. The COVID-19 vaccine (J&J/Janssen) is made using fetal retinal cells.

Fibroblast cell history

Fibroblast cells are the cells needed to hold skin and other connective tissue together. The fetal fibroblast cells used to grow vaccine viruses were first obtained from elective termination of two pregnancies in the early 1960s. These same fetal 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. For most cell lines, including fetal cells, it is around 50 divisions; however, because fetal cells have not divided as many times as other cell types, they can be used longer. In addition, because of the ability to maintain cells at very low temperatures, such as in liquid nitrogen, scientists are able to continue using the same fetal cell lines that were isolated in the 1960s.

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.

Retinal cell history

The retinal cells used to make the COVID-19 adenovirus vaccine (J&J/Janssen) were isolated from a terminated fetus in 1985 and adapted for use in growing adenovirus-based vaccines in the late 1990s.

Adenovirus-based vaccines that cannot replicate when administered to people need to be produced in cells that have the necessary gene to allow for large quantities of the virus to be made. The retinal cell line, called PER.C6, was adapted to enable production of these altered viruses.

Find out more in this Vaccine Update article.

Use of fetal cells and ability for vaccines to alter a person’s DNA

Even though fetal cells are used to grow vaccine viruses, vaccines do not contain these cells or pieces of DNA that are recognizable as human DNA. People can be reassured by the following:

• When viruses grow in cells, the cells are killed because in most cases the new viruses burst the cells to be released.
• Once the vaccine virus is grown, it is purified, so that cellular debris and growth reagents are removed.
• During this process of purification, any remaining cellular DNA is also broken down. To learn more about DNA and vaccine, visit the “Vaccine ingredients – DNA” page.

Learn more about fetal tissues used in vaccines by watching this short video, part of the Talking about Vaccines with Dr. Paul Offit video series.

For a more detailed description of the history related to the use of fetal cells, please read our article about the book, The Vaccine Race, by Meredith Wadman from the April 2017 Vaccine Update.

For an interview about the use of fetal cells to make the rubella vaccine, view this video interview, Stanley Plotkin: Pioneering the use of fetal cells to make rubella vaccine.

For additional information, check out the printable Q&A: “DNA, Fetal Cells & Vaccines,” English | Spanish.

Reference

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