SINGAPORE - While Covid-19 has infected about 65 million people worldwide, misinformation, fake news and conspiracy theories about the virus have probably spread to billions. Benjamin Seet and Ren Ee Chee clear the air about vaccines.

Q Can Covid-19 vaccines cause long term complications?

A It is too early to tell. Some complications are so rare that they are only seen once every one million to two million vaccinations, sometimes as long as one to two years later.

To date, only about 200,000 people have taken part in late-stage clinical trials for different Covid-19 vaccines worldwide, with the longest follow-up not exceeding four months. So it is still too early to draw firm conclusions.

What we do know is that major vaccine companies have been very transparent with their data, and have taken the unprecedented step of publishing their clinical trial protocols and interim results.

These are submitted to health regulators who assess the data with tough guidelines also applied to other vaccines.

There are no shortcuts when it comes to establishing the safety of a vaccine. We should expect no less with Covid-19 vaccines, despite their compressed development timelines.

Q Can an RNA vaccine change my DNA?

A There are some who claim that ribonucleic acid (RNA) vaccines can manipulate and change human deoxyribonucleic acid (DNA), resulting in a genetically-modified human.

Biologically, it just does not work that way. DNA uses one set of molecules for its genetic code, while RNA is made up of a different set of molecules.

The genetic information flow is one-way: DNA contains information that cells use to make messenger RNA (mRNA), which in turn provides a template to assemble proteins the body needs. The mRNA in Covid-19 vaccines cannot change human DNA.

Besides, 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 influenza virus is an RNA virus. When you catch the flu, you are in fact getting a massive dose of virus RNA. It can make you sick, but it does not change your DNA.

Q Does Covid-19 vaccination inject live viruses into your body?

A There are different types of Covid-19 vaccines.

One common vaccine is made up of dead viruses that have been chemically inactivated and are no longer infectious. These include the vaccines produced by Sinovac, Sinopharm and Valneva.

Another type of vaccine makes use of a common virus, called adenovirus, to transport a small fragment of Sars-CoV-2 gene into cells.

Such viral vectors are weakened so that they pose little risk of causing illness compared with a natural infection. Examples of vaccines that employ adenoviruses include the ones produced by AstraZeneca, Johnson & Johnson and CanSino, and the Russian Sputnik V vaccine.

Other leading programmes from Pfizer-BioNTech, Moderna, Novavax and Sanofi use biotechnology to manufacture either RNA or protein sub-unit vaccines, and do not make use of viruses, dead or live.

Q Is it better to get immunity from a natural infection rather than through vaccination?

A Both scenarios can produce high-quality immune protection. However, with natural infection, there is a risk of developing serious and potentially life-threatening illness, particularly in the elderly and those with pre-existing diseases like diabetes.

A small number of individuals may also develop "long-Covid", where they experience chronic symptoms including shortness of breath, headaches and even damage to the heart, lungs and kidneys. This condition is not fully understood, and there is no standard treatment.

It is also unlikely for entire populations to achieve herd immunity through natural infection.

Even in hard-hit communities, studies have shown that less than 10 per cent of people show immunity against Covid-19, which means that the remainder continue to be vulnerable.

Q If I get vaccinated, does it mean that I no longer need to wear a mask?

A It is important to continue wearing a mask to protect the people around you. Being vaccinated greatly reduces your risk of developing symptomatic Covid-19 disease, as well as the chance of getting severe disease. However, it may not stop you from getting infected without showing symptoms, or from spreading the virus to your family and friends.

Q Are vaccine companies implanting microchips into our bodies to control us?

A There are those who believe that information technology and pharmaceutical companies are in alliance to incorporate microchips into vaccines, in an attempt to track who has been vaccinated.

In more sensational versions of this hoax, there are claims that 5G networks and artificial intelligence will send signals to these microchips to control human behaviour.

While we are unable to establish the origin of this falsehood, it predates Covid-19 by almost a decade. Hoaxers tend to look for old stories and adapt them to the current situation to make the lies seem more convincing.

What we know is that certain vaccines contain metal salts, typically aluminium phosphate or aluminium hydroxide, to enhance the immune response. Such adjuvants - added to vaccines to improve immune response - have been used safely in vaccines for more than 60 years.

Vaccine adjuvants cannot be tracked or controlled by 5G.

In fact, mobile phones make better tracking devices that already control human behaviour.