We thank Mr Lim Teck Koon for his letter (Let people know there are other factors that can affect vaccine efficacy, May 3).
Any vaccine authorised for use in Singapore must be assessed for high safety and efficacy standards, and Covid-19 vaccines currently in use here have shown high efficacy rates of about 95 per cent. For the vast majority of those vaccinated, the Covid-19 vaccine is effective in preventing symptomatic disease, and can also reduce transmission to others.
While a small number of vaccinated individuals may still develop disease, vaccination protects against severe disease. Thus far, all such local cases have been asymptomatic or mildly symptomatic, and none has required oxygen support.
Vaccination is an important tool to help lower the risk of infection and severe disease, but it does not eliminate the risk completely. A vaccinated individual can still develop Covid-19 if he is exposed to a very large amount of the virus for prolonged periods of time.
This is why vaccination has to be adopted in tandem with public health and safe management measures such as mask-wearing and good personal hygiene, to reduce the risk of transmission of Covid-19.
Globally, Covid-19 variants have emerged, and some of these variants have been identified locally. The Covid-19 vaccines used in Singapore currently have been shown to be effective against the original Sars-CoV-2 virus and some variants such as the B1.1.7 strain, although efficacy against other new strains may be lower.
More data on this is being studied. While protection conferred against new strains may be lower, this immune protection is still substantial compared to the absence of protection in an unvaccinated person.
Personal health factors can contribute to the risk of infection and severe disease from Covid-19, and persons with chronic diseases are indeed at risk of more severe disease from Covid-19 infection. Vaccination has been shown in clinical trials to be equally efficacious in persons with chronic diseases, and it is therefore recommended for them to be vaccinated to protect themselves and those around them.
We strongly encourage all who are medically eligible to be vaccinated when the vaccine is offered to them, to keep themselves, their loved ones and those in the community safe.
Vernon Lee (Associate Professor)
Director, Communicable Diseases Division
Ministry of Health