The likelihood of a change in one's genes after taking a Covid-19 vaccine is very remote, experts said yesterday.
They were addressing the issue at a Straits Times Reset webinar on the A-Z of the Covid-19 vaccine in response to a reader who had asked if this could happen, and lead to a person getting cancer a few years later after the vaccination.
On Monday, Prime Minister Lee Hsien Loong announced that Singapore has approved the Pfizer-BioNTech Covid-19 vaccine for pandemic use here.
The vaccine is based on messenger RNA (mRNA) technology, which uses a chemical messenger to instruct cells to make proteins that mimic the outer surface of the coronavirus, which the immune system learns to recognise as a foreign invader and mounts a defence against.
Professor Ooi Eng Eong of Duke-NUS Medical School, who specialises in emerging infectious diseases, said: "Genetic information flows mostly in one direction, from the DNA to RNA to the protein. Think of it as you have a central library (where) you cannot bring the book out, but you can only copy the page that you need."
RNA cannot become DNA except in the case of certain viruses, known as retroviruses, with the human immunodeficiency virus (HIV) being the most famous example, he added. But for retroviruses to be able to do so, both their key enzymes are needed to convert RNA into DNA and then integrate the DNA into the genome.
These two enzymes must be in contact with the RNA and DNA, respectively. So even in HIV patients, the likelihood of the enzymes coming together with the RNA at the same time in the cell is very remote, Prof Ooi said.
"It is not easy. To us we think a cell is very small, but to the RNA - if the RNA is the size of one human being, the cell is the size of Singapore."
The panel said those who do not have HIV will be safe. Even if one has HIV, it is still safe as the chances of gene change are very remote.
Associate Professor Lim Poh Lian, director of the high-level isolation unit at the National Centre for Infectious Diseases and a member of the Covid-19 vaccine expert committee, added that the half-life of mRNA vaccines is very short. Once injected, it is quickly taken up by the body's cells and broken down after 48 hours.
"The role of the messenger RNA is basically to give instructions to make protein. And then the immune system actually develops protection. But RNA cannot integrate into the human genome. It actually never gets into the human DNA, because our genetic material is DNA, not RNA," she said.