The world's first dengue vaccine has been given the green light by the Health Sciences Authority (HSA), and will be available here in a few months.
The vaccine is most effective in people who have had dengue before and - underscoring the difficulty of vaccinating against a virus that has four distinct strains - is less effective against the two strains that are more common here.
But experts say it still holds promise against the mosquito-borne virus, which had infected 12,054 people (as of 3pm yesterday) so far this year, surpassing the number for the whole of last year.
The HSA, which has been studying the vaccine since March, fast-tracked its approval process because of public health concerns.
The decision to approve Dengvaxia was based on 24 studies conducted by vaccine manufacturer Sanofi Pasteur, which involved more than 41,000 people and showed the vaccine to be safe for use and effective against dengue.
Who should consider vaccination
Should you be vaccinated against dengue? Here are some potential scenarios to help you decide.
If you are a 40-year-old man who has had dengue before: Yes, you could consider the vaccine. Although you have had dengue before - the strain you had should be in your medical records - you might still contract another strain. Getting vaccinated could protect against future infections and severe dengue.
If you are a 19-year-old woman who is not sure if you have had dengue before: You should talk to your doctor about potential risks and benefits, as the vaccine offers more protection to those who have been infected with dengue before.
Your doctor may recommend that you undergo a blood test to determine if you have had a previous dengue infection.
If you are a 25-year-old man who is very sure you have never had dengue: You should talk to your doctor about the potential risks and benefits of getting vaccinated, so you can make an informed decision. If you are a 34-year-old woman who lives in an active dengue cluster, and would like to get vaccinated to protect yourself against the outbreak: The vaccine is administered in three doses over a year, so you will not be able to get immediate protection against the dengue outbreak just by getting vaccinated.
However, you may still want to get vaccinated to protect yourself against future infections.
Given in three doses over a year, the vaccine is approved for use in those aged between 12 and 45. Those outside this age group can be vaccinated if they so wish, but should seek a doctor's advice first.
Before the vaccine becomes available, the HSA will be embarking on efforts to educate doctors and the public on the benefits and limitations of the vaccine.
For people aged two to 16, Dengvaxia was shown to reduce the number of dengue cases by 60 per cent as compared with those who had not been vaccinated. This figure went up to 84 per cent when it came to preventing severe dengue infections in the same age group.
Additional studies showed that the vaccine was effective up to age 45, said the HSA yesterday.
But, though formulated against all four strains of the virus, the vaccine is less effective against the Den-1 and Den-2 strains, which account for three-quarters of the dengue cases here. Its efficacy is 50 per cent and 40 per cent respectively, compared with 75 per cent and 77 per cent for the other two strains.
Studies also showed that the vaccine provided better protection for those who had been exposed to the dengue virus than for those who had not, with efficacy at 81 per cent and 38 per cent respectively.
How much Dengvaxia reduces dengue infections will depend on how many people choose to be vaccinated, said Professor Ooi Eng Eong, deputy director of the emerging infectious diseases programme at Duke-NUS Medical School. "The larger this number, the greater impact vaccination would have on reducing the number of dengue cases in Singapore," said Prof Ooi, who is also a scientific advisory board member on dengue for Sanofi.
Professor Tikki Pang, a visiting professor at the Lee Kuan Yew School of Public Policy, said even if the vaccine is not as effective as hoped, it still presents a learning opportunity. "If you can prevent a certain number of cases, that, to me, is already worth it," he said.