Would you be concerned to know that the FDA is investigating how to make sure vaccines aren’t contaminated with retroviruses?
“Therefore, to ensure the safety of vaccines, our laboratory is investigating ways to activate latent viruses in cell lines and to detect the activated viruses, as well as other unknown viruses, using new technologies. We will then adapt our findings to detect viruses in the same types of cell substrates that are used to produce vaccines. We are also trying to identify specific biological processes that reflect virus activity.”Investigating Viruses in Cells Used to Make Vaccines; and Evaluating the Potential Threat Posed by Transmission of Viruses to Humans
Or like most folks, would it reassure you that they are continuing to work to make sure that our vaccines are safe.
Are Vaccines Contaminated with Retroviruses?
Vaccines are not contaminated with infectious retroviruses.
“Vaccines effectively reduce and prevent death and disease from many viral infections. However, vaccine production occasionally has been complicated by inadvertent contamination with adventitious agents that may have originated from cell substrates used to propagate vaccine strains.”Hussain et al on Lack of Evidence of Endogenous Avian Leukosis Virus and Endogenous Avian Retrovirus Transmission to Measles Mumps Rubella Vaccine Recipients
The issue first came up back in 1995 when it was discovered that MMR vaccines contained reverse transcriptase proteins. Researchers later found endogenous avian leukosis virus (ALV) and endogenous avian retrovirus (EAV) in those vaccines. Fortunately, they were not infectious and did not actually cause infections in any of the folks who got the vaccines.
Why were they there?
“Virtually all vertebrates studied, including humans, carry endogenous retroviral genomes as part of their natural genetic constitution.”Adventitious Viral Genomes in Vaccines but Not in Vaccinees
The MMR vaccine is grown in chick embryo tissue culture. Partial or complete genomes of these viruses can be present in chicken DNA. In fact, all chickens contain endogenous avian retroviral genome (EAV), and although that means they can release viral particles, they are noninfectious, so can’t make you sick.
Why weren’t they detected when the vaccines were first developed and approved?
The technology wasn’t available at the time.
“The absence of an infectious retrovirus in the MVVE material used in this study and in the CEF supernatant used in the previous study (which contained levels of RT activity similar to those of MVVE, based upon comparison with the positive control AMV RT dilution series) provides confidence regarding the safety of the earlier MV vaccines used in humans. The results of this study further demonstrate the absence of a known public health safety concern related to the presence of RT activity in chick-cell-derived vaccines and support World Health Organization recommendations for the continued use of chick-cell-derived vaccines in humans.”Shahabuddin et al on No Evidence of Infectious Retroviruses in Measles Virus Vaccines Produced in Chicken Embryo Cell Cultures
And once the technology was available, these retroviruses were thoroughly investigated and found to not be a safety hazard. That’s not surprising though, as no problems were previously detected by our vaccine safety systems.
So why are we still talking about retroviruses in vaccines?
More on Vaccines and Retroviruses
- FDA – Investigating Viruses in Cells Used to Make Vaccines; and Evaluating the Potential Threat Posed by Transmission of Viruses to Humans
- WHO – Reverse transcriptase activity in chicken-cell derived vaccine : WHO consultation, April 1998
- CDC – Adventitious Viral Genomes in Vaccines but Not in Vaccinees
- Study – No Evidence of Infectious Retroviruses in Measles Virus Vaccines Produced in Chicken Embryo Cell Cultures
- Study – Lack of Evidence of Endogenous Avian Leukosis Virus and Endogenous Avian Retrovirus Transmission to Measles Mumps Rubella Vaccine Recipients
- Study – Detection of reverse transcriptase activity in live attenuated virus vaccines.
- Study – Assessing the significance of reverse transcriptase activity in chick cell-derived vaccines.
- Study – Reverse transcriptase activity in chicken embryo fibroblast culture supernatants is associated with particles containing endogenous avian retrovirus EAV-0 RNA.
- Study – 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.
- Deep sequencing reveals viral vaccine contaminants