A leading biologist whose team recently discovered that the coronavirus that causes Covid-19 may be able to insert its genes into human DNA has said there is no cause for alarm over vaccines that mimic the process of infection.

The discovery by Professor Rudolf Jaenisch and researchers at the Massachusetts Institute of Technology, stirs up a hornet’s nest because mRNA vaccines, including those made by Pfizer/ BioNTech and Moderna, operate in similar ways to the virus to trigger an immune response.

But he said there is “absolutely no evidence” that these vaccines would alter human DNA.

Jaenisch, a pioneer in the field of transgenics, added that if they are found to do so it may actually be a good thing, saying: “One could speculate that such an integration, if indeed happening, might result in more long-term expression of the antigen [a substance that causes the immune system to create antibodies] and thus be beneficial.”

Though some researchers said the finding was unexpected and could fundamentally change our understanding of the virus, Jaenisch said it should not be used as an argument against vaccination.

The mRNA vaccines only use parts of the virus’ genes known as messenger RNA, not the whole sequence. Because these gene segments do not include components that are important for viral functions, adverse effects such as triggering unwanted mutations should be minimal.

Jaenisch however admitted that “at this point we just do not have much information” on certain questions concerning the safety of mRNA vaccines, such as whether more research should be conducted before the mass vaccination of entire nations.

Jaenisch’s caution reflects a dilemma in the research community when using new technology to battle a new virus. Before the pandemic, and despite decades of efforts, no mRNA vaccines had completed clinical trials but now the Pfizer/BioNTech and Moderna vaccines have completed the process.

The current large-scale vaccination programmes in many countries have so far only received authorisation for emergency use.

The risk that an mRNA vaccine will change human DNA and cause unexpected diseases is small compared with the catastrophic damage caused by the ongoing pandemic, but there are concerns in the health care community about the technology’s safety and potential side effects, especially in the long run.

In a survey of nearly 1,000 health workers (mostly doctors) in Hong Kong last week, only 22 per cent said they would use the Pfizer/BioNTech jab, with the majority preferring vaccines made using more traditional methods.

The MIT study, which has not yet been peer-reviewed, received enormous attention in the global research community.

Nobel Prize winner David Baltimore told Science magazine the results were “impressive”. The coronavirus was thought to be harmless to human DNA, because its genes were unable to enter the cell nucleus, where the DNA was kept.

Some researchers have asked Jaenisch to retract the paper because it could affect people’s confidence in the new vaccines.
“This preprint has already attracted the attention of the anti-vaccine crowd,” said a commentator on biorxiv.org, where the study was posted.

Some questioned the validity of their findings. The discovery was made in a Petri dish, and what really happens in the human body could be quite different, according to some critics.

The mRNA vaccines are by far the most powerful and effective weapon against the coronavirus, promising an efficacy rate of more than 90 per cent.

The vaccines can deliver viral genes into many kinds of human cells and turn them into a factory producing the virus’s spike protein. Our immune system then remembers these unique proteins and stages a swift, precise response when it encounters the real virus.

But if the viral genes carried by the mRNA vaccine could get into the nucleus through the previously unknown mechanism described by the new study, there is a chance that it could alter our DNA and cause unexpected mutations.

Under the guidelines used in many countries, the mRNA vaccine might be considered a gene therapy.

An important reason why it could receive emergency use approval in these countries is that the vaccine developers promised that their product would not mess up human DNA.

The mRNA has a single stranded structure and is believed to disintegrate quickly after entering the cells – which means two shots of the vaccine are needed to strengthen the effect.

Jaenisch’s study found the viral genes can make use of LINE-1, a common enzyme in the human body, to get into the nucleus and insert themselves in our DNA. The nucleus is protected by a lipid membrane, but not entirely sealed, allowing materials to come in and out with the help of some agents such as LINE-1.

Jaenisch and his colleagues believe their findings could explain why some recovered patients continued to shed viral genes.

Some of these patients tested positive months after the disappearance of all symptoms. If their DNA had been modified by the virus, they could be generating genetic materials linked to the virus for longer periods than previously thought, according to the researchers.

Many viruses are able to change our DNA. HIV, for instance, can hijack the nucleus and turn cells into virus production plants.

Some researchers believe the LINE-1 enzyme is in fact a remnant from an HIV-like virus that infected early human beings and its genes were integrated with the survivors’ DNA to become part of our body today.

Professor Gao Daxing, a researcher with the Key Laboratory of Innate Immunity and Chronic Disease in Anhui, said traditional vaccines use inactivated viral strains, and doctors know more about their safety risks and side effects thanks to decades’ worth of data.

But these traditional vaccines are fighting an uphill battle in the global pandemic. The production of traditional doses needs guarded facilities with high biosafety standards because they have to grow the virus in a lab before killing it to make the vaccine.

The virus is also mutating constantly, and it could take months for vaccine developers to catch up with a new strain using the old technology.

The massive roll out of mRNA vaccines, mostly in Western countries, is a “grand experiment”, said Gao. The new vaccines can be mass produced more easily and updated quickly to counter mutations.

The data collected from these vaccination programmes would help improve future products.

“The current product is version 1. It may have this or that problem. But things will get better with upgrades to version 2, 3 or more,” Gao said. “The mRNA vaccine is probably a path to the future.”

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