Have you heard the latest conspiracy theory – that the CDC is hiding MMR excipients? Depending on who you are supposed to believe, “they” recently removed either WI-38 or MRC-5 DNA and Cellular Protein from the MMR II excipient list.

Is it true?
Is there a conspiracy at CDC to hide vaccine ingredients?
Is the CDC Hiding MMR Excipients?
Of course not!

As most folks should know by now, it is hard to change and hide stuff on the Internet, as nearly all pages are archived.
What does that mean?
You can easily look up and see how a page looked yesterday, last week, last month, or last year. Or in the case of the CDC Vaccine Excipient and Media list, over 12 years ago!
And guess what?

MRC-5 cells were never on the MMR list because the MMR vaccine isn’t made with MRC-5 cells!
The MMR vaccine is made with chick embryo fibroblasts and WI-38 human diploid lung fibroblasts, but since neither remain in the final vaccine, they aren’t on the latest excipient list. They can still be found in vaccine’s package insert.
Substances used in the manufacture of a vaccine but not actually listed as contained in the final vaccine can be found in the package insert for the vaccine, but are no longer shown on the excipient table.

This change to the excipient list was made in 2019.
Why the change?
Probably because this more accurately reflects what’s in the vaccine! Remember, many of the things that are used to make a vaccine get filtered out along the way.
Interestingly, while chick embryo fibroblasts were on the original excipient list, in 2007, WI-38 human diploid lung fibroblasts weren’t.

They were briefly added, but then both were removed with the change to the excipient list in 2019.

And that’s why anti-vax folks think that there is some conspiracy to hide them.

A conspiracy to hide these excipients that explains that why excipients are not included on the list and not only tells you where to find them, in the vaccine’s package insert, but also includes a link to find them?

Have anti-vax folks run out of things to be scared of?
Still think that there is a conspiracy to hide excipients?
Consider that the Vaccine excipient table at the Institute of Vaccine Safety, maintained since 2006, has never listed WI-38 cells…
More on Anti-Vax Conspiracy Theories
- A Crazymother Visits Her Pediatrician to Talk About Vaccines
- The CDC Vaccine Price List Conspiracy
- About Those Binders of Anti-Vaccine Misinformation
- Why Is a Toxicologist Making Claims About Vaccines and Autism?
- Risks and Benefits of Vaccines – Anti-Vax Edition
- Is 100% of Injected Aluminum Absorbed?
- Inappropriate Use of Vaccine Studies
- More Questions to Help You Become a Vaccine Skeptic
- FDA – Vaccines Licensed for Use in the United States
- FDA – Common Ingredients in U.S. Licensed Vaccines
- CDC – Vaccine Excipient Summary
- Vaccine Excipients per 0.5 mL dose
- What’s all that other stuff in my medicine?