Virus Enzyme Found in MMR Vaccine

Virus Enzyme Found in MMR Vaccine

by Barbara Loe Fisher

Swiss scientists have reported finding an enzyme, reverse transcriptase, in the live measles and mumps vaccine, which has been traced back to chickens whose cells are used to create the vaccines.1 Reverse transcriptase (RT), which copies RNA into DNA, has also been detected in yellow fever and some influenza vaccines prepared in chicken embryo cells.

Scientists Puzzled

RT activity is associated with the presence of retroviruses, a class of viruses that can permanently alter the genes of the cells they infect. AIDS is a retrovirus. Scientists at Merck & Co., the US manufacturer of MMR vaccine, are reportedly trying to find out where the RT came from. One possibility is that the RT activity in MMR vaccine signals the presence of an avian leucosis virus (AVL), a retrovirus that infects some birds and can cause a leukemia-like illness.

Another possibility is that the chickens used to make the vaccine carry RT coding genes derived from retroviruses that infected the species tens of thousands of years ago.

CDC Says to Keep Vaccinating

The RT activity in MMR vaccine was detected by Swiss scientists using advanced testing technology called product-enhanced reverse transcriptase (PERT). The Centers for Disease Control and Prevention (CDC) responded to the report in the Dec. 9, 1995 Washington Post2 about the Swiss discovery by stating that, “The World Health Organization has reviewed these findings and has concluded that these vaccines should continue to be used to prevent the diseases against which they are directed.”

The CDC maintained that, “The likeliest explanation for finding reverse transcriptase activity is that, in the distant past, an avian retrovirus integrated itself into the ancestors of the chickens that laid the eggs that were used to produce the chick embryo fibroblasts used for vaccine production… However, studies to date have not detected any evidence of a virus which can be transmitted to and replicate in humans.”

Do Chicken Viruses Belong in Humans? Independent researchers have started to express concern that using animal tissues for production of human vaccines, especially live vaccines such as MMR and polio, could be facilitating the inter-species transfer of viral infection from animals into man causing as yet undetected and unevaluated negative health effects on humans. Of particular concern is the fact that transfer of the whole animal virus into man does not have to take place in order for latent viral infection and genetic change to occur. If portions (genes) of animal viruses are introduced into humans, they have the potential to interact differently with each individual’s immune system and DNA and cause disease

Learn more about this topic:

Tsang SX, Switzer WM et al. Evidence of Avian Leukosis Virus Subgroup E and Endogenous Avian Virus in Measles and Mumps Vaccines Derived from Chicken Cells: Investigation of Transmission to Vaccine Recipients. J Virol 1999; 73(7): 5843-5851.

Johnson JA, Heneine W. Characterization of Endogenous Avian Leukosis Viruses in Chicken Embryonic Fibroblast Substrates Used in Producing Measles and Mumps Vaccines. J Virol 2001; 75(8): 3605-3612.

Hussain AI, Johnson JA et al. Identification and Characterization of Avian Retroviruses in Chicken Embryo-Derived Yellow Fever Vaccines: Investigation of Transmission to Vaccine Recipients. J Virol 2003; 77(2): 1105-1111.

Rubin H. The early history of tumor virology: Rous, RIF, and RAV. Proc Natl Acad Sci 2011; 108(35): 14389-14396.

Birmingham CL, Dupont D et al. Detection of Avian Retroviruses in Vaccines by Amplification on DF-1 Cells with Immunostaining and Fluorescent Product-Enhanced Reverse Transcriptase Endpoint Methods. J Clin Microbiol 2013; 51(5): 1496-1504.

Virus Enzyme Found in MMR Vaccine