mRNA Vaccines

On 14 December 2020, The Health Sciences Authority (HSA) granted authorisation, under the Pandemic Special Access Route (PSAR), for the Pfizer-BioNTech COVID-19 vaccine to be used in Singapore for the prevention of the Coronavirus Disease 2019 (COVID-19). The vaccination regime by Pfizer-BioNTech requires two doses of vaccine to be administered 21 days apart, in individuals aged 16 years and above.

The vaccine demonstrated a high vaccine efficacy of 95%. This means that there is a 95% reduction of symptomatic COVID-19 disease in a vaccinated group of people as compared to a similarly sized group of unvaccinated people. This vaccine efficacy was observed to be consistent across different age groups that are 16 years and older in over 40,000 clinical trial participants, whose ages ranged from 16 to 91 years.

Based on the data accrued to-date, the safety profile of the Pfizer- BioNTech COVID-19 vaccine was generally similar to that of other vaccines used in the immunisation against other diseases. Some people may experience side effects such as pain, redness, swelling at the injection site, fatigue, headache, muscle ache, fever, chills, vomiting, diarrhoea and joint pain after vaccination. While not everyone will experience these side effects, they are common and expected as part of the body’s natural response to build immunity against COVID-19. These side effects usually dissipate within a few days. As a precautionary measure, pregnant women, immunocompromised persons, and those under the age of 16 should not receive the Pfizer-BioNTech vaccine as the safety and efficacy data on this group of persons is not available yet.

How does the vaccine work?

Unlike traditional methods of injecting a weakened or a dead form of virus into the body, the Pfizer-BioNTech COVID-19 vaccine is a messenger RNA vaccine, also known as an mRNA vaccine. When administered into the muscle, the mRNA vaccine gives instructions to our muscle cells to create a harmless protein piece, which is also known as the “spike protein”. After the protein piece is created, the cells break down the instructions and gets rid of it.

Next, the cells display the protein piece on its surface. Our immune systems recognise that the protein does not belong there and starts building an immune response to it by making antibodies. This process also occurs when there is a natural infection against COVID-19.

At the end of the process, the body would have learnt to protect itself against a future infection. The benefit of mRNA vaccines, like all vaccines, is that those vaccinated gain this protection without ever having to risk the serious consequences of falling ill with COVID-19.

mRNA vaccines are new, but not unknown

mRNA vaccines have been studied previously for diseases such as influenza, zika virus, rabies, and cytomegalovirus (CMV). Beyond vaccines, cancer research has explored using mRNA to trigger the immune system to target specific cancer cells.

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Article reviewed by Dr Michael Wong, Deputy Medical Director, Raffles Medical Group.

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