SINGAPORE - The Pfizer-BioNTech vaccine is safe and effective for children aged 12 to 15, said the Expert Committee on Covid-19 Vaccination on Friday night (May 21), in response to an open letter penned by some doctors which was later retracted.

"The Pfizer-BioNTech vaccine is currently the only Covid-19 vaccine anywhere in the world that has been authorised for use in adolescents aged 12 to 15 years," the committee said.

"The safety profile of the vaccine is consistent with the known safety profile in the adult population and the standards set for other registered vaccines used in the immunisation against other diseases," it said.

On Thursday night, 12 doctors posted an open letter calling for children to be given traditional Covid-19 vaccines instead of mRNA ones.

Singapore currently uses two vaccines - Pfizer-BioNTech and Moderna. Both use mRNA technology which gets cells to make a protein piece on its surface that triggers an immune response.

The Health Sciences Authority (HSA) is still studying the Sinovac vaccine, which is made using a traditional method where killed virus is used. The body recognises this and mounts an immune response.

Eleven of the 12 doctors later retracted the letter, saying that "some of our thoughts may be misunderstood by some laypersons. We will henceforth, ponder in a more professional and private forum".

Commenting on the letter on Saturday (May 22), Senior Minister of State for Health Koh Poh Koon said: "As a doctor, I am aghast and disappointed by the unscientific and unprofessional way in which these doctors have interpreted scientific evidence and conducted themselves.

"It creates confusion and fear in the public and propagated myths and untruths," he added in a Facebook post.

"I'm glad to see other fellow doctors stepping up and speaking out against such untruths. I urge all of us to get our information from reliable sources. The fight against Covid-19 will continue to evolve as new data and development present themselves. We need to navigate this with scientific rigor and not let our emotions or personal biases create more confusion," he said.

The open letter was posted on the HardwareZone forum and also appeared in at least one Telegram chat on vaccination. The retraction appeared in some chats and was confirmed by Dr Paul Yang, the author of the letter.

Dr Yang, a general practitioner, told The Straits Times: "The letter was posted prematurely. It is a letter of advice to my church parents' group. The technical issues are unfortunately too complicated, but accurate factually."

The open letter, which was addressed to "all parents deciding to vaccinate or not to vaccinate their child", caused concern among some parents of young children, especially as two of the doctors who signed it had also signed an open letter in February last year urging people to wear masks when going out - about two months before it was made mandatory here.

In its response on Friday, the Expert Committee on Covid-19 Vaccination said it had recommended that the Pfizer vaccine be used among those aged 12 to 15 years following HSA's approval.

"Our assessment remains that the Pfizer-BioNTech vaccine is safe and efficacious for this age group. There is currently no credible evidence of a inactivated virus vaccine demonstrating a high vaccine efficacy and safety profile among this age group," it said.

The statement said the committee had noted the contents of the open letter and that 11 of the 12 doctors have retracted their statement.

The committee said the Singapore population, including adolescents, continue to remain at risk of infection and onward transmission to their close contacts.

"This is seen in the recent local cases and outbreaks involving schoolgoing children who had been infected with Covid-19 and transmitted it to their family members and schoolmates," it said.

While the international experience is that Covid-19 appears milder in the younger age groups, there remains a risk of complications and long-lasting symptoms in children and adolescents.

"The expert committee therefore recommends that with the availability of a safe and efficacious vaccine, all eligible persons should receive the vaccine to attain as high a population coverage of Covid-19 vaccination as possible."

Responding to what was in the open letter, the committee said: "Covid-19 vaccines cannot alter your DNA. The Pfizer-BioNTech Covid-19 vaccine comprises messenger RNA (mRNA) that contains the instructions to enable the vaccine recipient to build a protein component of the Sars-CoV-2 virus ("spike protein").

"The spike protein does not cause infection, but is recognised by the body's immune system as foreign. The body then mounts an immune response and produces antibodies that protects against future infection by the virus. The vaccine mRNA is broken down by the body rapidly after the spike protein is built. The mRNA is unable to produce more copies of itself, and cannot enter the nucleus of the human cells where human genetic material ("DNA") is stored.

"Since the human genome is made up of DNA, it is not biologically plausible for the vaccine mRNA to be integrated or to interfere with the DNA of the vaccine recipient."

The chairman of the expert committee, Associate Professor Benjamin Ong, added that the vaccine was assessed to be safe and effective for the 12-15 age group "after careful assessment and deliberation of the available clinical data". "There is no inactivated Covid-19 vaccine approved for use in children yet."

The committee said that with more than 200 million doses of the Pfizer vaccine used worldwide, "there is currently no evidence for rare but serious effects of the Pfizer-BioNTech Covid-19 vaccine beyond anaphylaxis". Anaphylaxis is a severe allergic reaction that can kill unless treated promptly.

The committee and HSA will continue to monitor and review evidence and information that emerge from further ongoing studies on long-term safety and efficacy, it said.

"Singapore remains at risk of a surge in cases and it is therefore important that we achieve as comprehensive a coverage of Covid-19 vaccination as possible across the entire population. We strongly encourage all persons who are medically eligible to be vaccinated when the vaccine is made available to them."

Some doctors and scientists said they were aghast at what was put out in the open letter.

Professor Ooi Eng Eong of Duke-NUS Medical School, an expert on emerging infectious diseases who has been involved in developing an mRNA vaccine, said their argument is "pseudoscience" and based on "a lot of misunderstanding of molecular biology and immunology".

He said: "The development of mRNA vaccine, although rapid, was based on more than 20 years of painstaking research. This vaccine technology was not assembled in a hurry. Instead, the world was fortunate that this technology matured at a time when it was needed most."

Dr Desmond Wai, a gastroenterologist in private practice, took exception to the open letter because "as a doctor, if I have an academic question, I should ask the Ministry of Health (MOH), or the experts, directly - especially if my viewpoint/interpretation is different from the mainstream".

He added: "Giving an opinion in the public domain causes confusion to the public. I am aware that as a doctor, the public will take my opinion seriously. So all the more I should be careful when I give opinions in public."

Dr Kenneth Lyen, a paediatrician in private practice, also disagreed with several of the points raised in the letter. He said: "We are all concerned about the safety and efficacy of vaccines. Life is full of risks and balances. It is safer to be vaccinated than to cross a Singapore street. The choice is yours."

Debunking the open letter

Prof Ooi and Dr Lyen also debunked some of the points raised in the letter about why children should not be given the mRna vaccines.

• The letter referred to an article by authors from three universities in the United States (Whitehead Institute for Biomedical Research, Harvard University and Massachusetts Institute of Technology) published in the Proceedings of the National Academy of Sciences of the United States last year, and noted that "mRNA themselves are very fragile in the human body and are easily attacked by ribonucleases that are distributed very widely in our body".

It also said: "Reverse transcriptase, which converts RNA to DNA, is very troubling. It is not naturally found in our body but becomes readily available if you are very sick with a chronic virus, like hepatitis B."

Prof Ooi said that if that statement were true, "persons living with HIV and hepatitis B would have their entire genome scrambled by the virus".

"Whole human genome sequencing, which is now increasingly common, would have discovered dengue and other RNA virus genome being incorporated into the DNA of these persons. This has never happened."

Dr Lyen added: "The vaccine mRNA degrades within a short period of time, and the integration risk is considered negligible."

• The letter stated that "mRNA vaccines do not stop adults from transmitting Covid-19 variants of concern. We can assume that this will also be the case with children".

Prof Ooi said several studies have consistently found that mRNA vaccination reduces the rate of transmission. The same should apply to children.

Dr Lyen added: "No vaccine is 100 per cent protective. Therefore, some vaccinated individuals can still catch Covid-19, and spread it to others. If both adults and children are protected against Covid-19, they are less likely to catch Covid-19, and therefore the virus will not replicate in the body, and if there is no replication, there is no chance of mutations."

• The letter said "it is not very wise to try on Singaporean children novel mRNA technology when they do not really need it and it does not effectively stop them from becoming vectors". It also said: "The good news is that children are doing amazingly well, without any Covid-19 vaccines."

Prof Ooi said vaccines "are not being tried in children". They are licensed for use in children after clinical trials have proven them to be safe, he said.

Dr Lyen added: "While children may not be so seriously affected, in that they do not usually require intensive care, they can still fall quite seriously ill. The statement also overlooks another important reason for vaccination, and that is to prevent spread to other members of the family and to other people in contact with them."

• The letter said "killed-virus technology has been around for decades and has a very long and safe track record. For mRNA, long-term side effects are unknown and unstudied. This point is supported by all experts".

Prof Ooi disputed this. While killed-virus vaccines are an older technology, such vaccines have "been associated with the development of severe disease in those vaccinated", he said.

One such vaccine was developed to prevent respiratory syncytial virus, a common childhood respiratory illness. Development of that vaccine in the 1960s was stopped because it caused more severe disease.

Although Singapore has bought, and received, the more traditional Sinovac vaccine, it has not been approved for use here, as information on its safety and effectiveness has not been sufficient for HSA, the regulator.

• The letter said "we have no evidence that the mRNA vaccines are safe in the longer term (10 to 20 years)".

Dr Lyen said: "If the risk of not vaccinating and getting Covid-19 results in severe long-term illness and even death, then one should vaccinate. Medical science progresses at incredible speed, so we should not worry about what happens 10 to 20 years later. We will deal with future problems if and when they arise."

Added Prof Ooi: "There is absolutely no evidence to support the notion that there are vaccines that can cause problems 10 to 20 years after vaccination. This is a myth."