Basis for claim: a 2018 SEC filing from Moderna, Inc.
https://www.sec.gov/Archives/edgar/data/1682852/000119312518341958/d611137ds1a.htm#toc611137_6
Page 20 includes the following text:
Currently, mRNA is considered a gene therapy product by the FDA. Unlike certain gene therapies that irreversibly alter cell DNA and could act as a source of side effects, mRNA based medicines are designed to not irreversibly change cell DNA; however, side effects observed in gene therapy could negatively impact the perception of mRNA medicines despite the differences in mechanism. In addition, because no product in which mRNA is the primary active ingredient has been approved, the regulatory pathway for approval is uncertain. The number and design of the clinical and preclinical studies required for the approval of these types of medicines have not been established, may be different from those required for gene therapy products or may require safety testing like gene therapy products. Moreover, the length of time necessary to complete clinical trials and to submit an application for marketing approval for a final decision by a regulatory authority varies significantly from one pharmaceutical product to the next, and may be difficult to predict.
Paraphrased:
In this 2018 filing, Moderna is expressing uncertainty about the approval process for its technology because that FDA has not developed a framework for mRNA based medicines, so it could be lumped in with gene therapy products, even though it is not a gene therapy.
Key point #1: whether Moderna thought that FDA would classify mRNA products as "gene therapy" is irrelevent to the question of whether they actually are gene therapy, which the context clearly explains they are not.
Key point #2: mRNA vaccines are not discussed in this document at all. Medicines and vaccines are distinct drug classifications.
Currently, the FDA describes "gene therapy" as follows:
Human gene therapy seeks to modify or manipulate the expression of a gene or to alter the biological properties of living cells for therapeutic use.
https://www.fda.gov/vaccines-blood-biologics/cellular-gene-therapy-products
This is a complete list of all approved gene therapy products. This list does not include mRNA vaccines because they are not gene therapy:
https://www.fda.gov/vaccines-blood-biologics/cellular-gene-therapy-products/approved-cellular-and-gene-therapy-products
Dr Adam Taylor, a virologist and research fellow at the Menzies Health Institute, Queensland, Griffith University, said to Reuters: “As mRNA is genetic material, mRNA vaccines can be looked at as a genetic-based therapy, but they are classified as vaccines and are not designed to alter your genes... Gene therapy, in the classical sense, involves making deliberate changes to a patient’s DNA in order to treat or cure them. mRNA vaccines will not enter a cell’s nucleus that houses your DNA genome. There is zero risk of these vaccines integrating into our own genome or altering our genetic makeup.”” https://www.reuters.com/article/factcheck-covid-mrna-gene-idUSL1N2PH16N
Study: https://www.mdpi.com/1467-3045/44/3/73
This study has been widely misunderstood. The authors later published a Q&A, saying:
"this study does not investigate whether the Pfizer vaccine alters our genome" and "there is no reason for anyone to change their decision to take the vaccine based on this study."
https://www.lunduniversity.lu.se/article/qa-covid-19-vaccine-study-gains-attention
The study demonstrated that mRNA had converted to DNA in vitro using a huh7 liver cancer cell line. Cell lines differ from cell lines in living organisms. huh7 liver cancer cells are not normal, healthy cells.
An MIT study published 2021-04-19 showed that SARS-CoV-2 (the virus, not the vaccine) RNA "can be reverse-transcribed and integrated into the genome of the infected cell"
Study: https://www.pnas.org/doi/10.1073/pnas.2105968118 (2021-04-19)
A followup study published 2023-02-25 reaffirmed this finding and also looked at whether the same thing happens with mRNA from COVID vaccines. Author Rudolf Jaenisch stated "We need to do further testing, but our results are consistent with vaccine RNA not integrating"
Source: https://biology.mit.edu/new-research-supports-finding-explaining-why-some-patients-may-test-positive-for-covid-19-long-after-recovery/ (2023-02-28)
Followup Study: https://www.mdpi.com/1999-4915/15/3/629 (2023-02-25)
Chance That COVID-19 Vaccines Are Gene Therapy? 'Zero' (WebMD)
https://www.webmd.com/lung/news/20210719/covid-19-vaccines-not-gene-therapy
VIDEO: How do mRNA COVID-19 vaccines work? (PBS NewsHour)
https://www.youtube.com/watch?v=7DlcRSvuvnw