I refer to Mr Edward Ng's letter (Is Covid-19 vaccine safe for the vulnerable?, Jan 22). Older adults have a higher risk for Covid-19, which is why they have been given a higher priority for access to Covid-19 vaccination.

The phase two/three clinical trials by Pfizer-BioNTech included persons with medical conditions such as hypertension, diabetes, asthma, lung, liver and kidney disease, as well as chronic HIV, hepatitis B and hepatitis C infection. The vaccine was found to have similar efficacy and safety for persons with these co-morbidities.

Persons with a history of cancer that is in remission can get vaccinated. However, if they have untreated cancer including those in palliative stage, or are undergoing chemotherapy, immunotherapy, or radiation therapy, we recommend them to defer Covid-19 vaccination until after treatment is completed.

For such persons who cannot be vaccinated, it is a good idea for their household members and caregivers to receive the Covid-19 vaccine. This approach is called "cocooning", a form of ring vaccination to protect the most vulnerable.

There is no evidence at this time that persons with neurological disorders or auto-immune conditions have any different vaccine efficacy or safety from others. Hence we would like to reassure the public that Covid-19 vaccination is generally safe for persons with medical conditions, and they are encouraged to consult their doctors for questions about their suitability for Covid-19 vaccine.

Lim Poh Lian (Associate Professor)

Head, Travellers' Health and Vaccination Clinic, Tan Tock Seng Hospital

Senior Consultant, National Centre for Infectious Diseases

Member, Expert Committee on Covid-19 Vaccination