Before her retirement in 2011, Dr Jacqueline Mok was a Paediatric Consultant for Community Child Health, Lothian Health Board, and was a member of the Royal College of Paediatrics and Children's Health. Her research has mainly focused on HIV and AIDS in infants and children, with a particular focus on mother-to-child transmissions. She has worked extensively on research for HIV therapies that are not only safe for children, but also for expectant mothers. Her research has expanded beyond HIV-infected children to include HIV-affected children: those who have mothers who are HIV positive.

Beginning in 1985, during the HIV outbreak in Edinburgh, she was responsible for running paediatric HIV services for Lothian Health Board. Prior to her position, Dr Mok was a Senior Registrar in Paediatrics, and had only just returned from completing a year of training for respiratory paediatrics in Toronto, Canada. Having returned in September, she was offered the position in October.

When she was asked to take on the job of caring for children who were at risk from HIV, she chose to travel to the United States first in order to learn more about HIV in children. This was a new field, having only been studied for two years, and United States medics were the first to recognise and conduct research in this area. Whilst in the United States, she found that the outbreak in Edinburgh was rather unique as some of the young mothers found with the HIV virus were not showing symptoms of illness.

After taking up the position of looking after young mothers and their children, Dr Mok faced a number of challenges. As HIV in children was a brand new research area, for much of the job Dr Mok was working in unknown territory. Another issue was that virtually nothing was known about the transmission of HIV.

In the early stages of her position, Dr Mok started a clinic for HIV-infected children at the City Hospital. In addition to the clinic set up in Ward 15 (Paediatric Ward) of the City Hospital, Dr Mok also completed home visits, and the clinic gained funding from the Scottish Office, Sick Children's Trust, and Royal Infirmary Trust. This clinic was the first family clinic in the UK. Eventually, the clinic moved from its space at the City Hospital and was granted use of Ward 8 (Ward for Infectious Diseases) at the Royal Hospital for Sick Children.

While the main part of Dr Mok's job was to care for children born to HIV-infected women, a secondary part of her job involved the possible removal and rehousing of children, when a mother was deemed unfit. Therefore, she worked closely with social workers and foster carers, and would run special lessons in order to educate foster carers on HIV positive children.

Dr Mok also worked closely with schools to educate staff regarding HIV transmission, in order to allow HIV positive children to go to school. Prior to this, many schools did not have any information on how best to handle children with HIV as it was believed they would never live long enough to go. While this was true for some children, a large majority of them were able to live normal lives, which included attending school.

With children growing older than originally expected, it was necessary to educate them about HIV and its treatments. As such, Dr Mok worked closely with PARC (Paediatric AIDS Resource Centre), which focused on the education of children on HIV and HIV treatment, in order to ensure those who were HIV-infected or HIV-affected fully understood what was happening. As a result of this, Dr Mok and some of her colleagues published several children's books explaining topics such as examination appointments, treatment, and death.