With flu cases rising in Singapore, how can you protect yourself?

With the year-end flu season round the corner, it is probably time to get your flu shot, which is available at polyclinics, general practitioner (GP) clinics and retail pharmacies.

Infectious diseases experts recommend the flu vaccination, particularly for seniors and those with underlying medical conditions, as they face a higher risk of complications from severe influenza infections. Vaccination is recommended even for those without travel plans.

Though the year-end flu season has yet to begin, more people here have been down with the flu.

Data from the Communicable Diseases Agency (CDA) shows polyclinic visits for acute upper respiratory infections - predominantly caused by viruses such as the influenza virus - have gone up by 8 per cent in recent weeks. The daily average has risen from about 2,520 visits in late August to early September to about 2,730 visits.

A CDA spokeswoman said influenza viruses circulate year-round in Singapore, with peaks typically observed in May to August, and December to March.

Simply Science looks at the flu virus and how vaccines can protect those at high risk.

Q: How do flu vaccines work and what are the side effects?

Dr Stephanie Sutjipto, an infectious diseases consultant with the National Centre for Infectious Diseases, said once the vaccination has been administered, the body will start to recognise the vaccine antigens, which are proteins that will trigger the immune response. It will also activate the B cells - white blood cells that produce the protective antibodies.

Information on the national healthcare portal HealthHub mentions minor side effects such as:

• Soreness, redness or swelling where the shot was given
• Muscle aches
• Runny nose
• Headache
• Low-grade fever
• Cough
• Sore throat

Side effects will usually last one to two days. On very rare occasions, there could be severe allergic reactions.

Q: Why does the protection not kick in immediately after vaccination?

The body takes about two weeks to build up immunity against the flu virus.

Adjunct Associate Professor Jolene Oon, senior infectious diseases consultant at the National University Hospital's department of medicine, cautioned that during this period, a vaccinated person may still be susceptible to infection if exposed to the flu virus, hence the recommendation to be vaccinated ahead of the flu season.

Q: Why does the vaccine change every six months? Does its name suggest I should take it only if I am travelling to either hemisphere?

Prof Oon said the influenza virus mutates constantly, leading to new strains circulating worldwide each year.

The World Health Organisation monitors circulating strains globally, and updates its recommendations for the vaccine formulation half-yearly.

Dr Sutjipto said the Northern Hemisphere vaccine is meant to protect against the strains predicted to circulate during winter in the north, meaning it can be used from October to March. Conversely, the Southern Hemisphere vaccine can be used from April to September during the southern winter.

The CDA spokeswoman said influenza vaccination is recommended for travellers regardless of destination, and is particularly important for those travelling to countries in winter; areas with heightened influenza activity; or crowded settings such as cruises, sporting events and pilgrimages.

Q: Should I get the vaccine each time it changes? Will there be side effects if I do so?

Prof Oon said for most people, one jab a year is sufficient "unless they intend to travel a lot or there is a significant change in the strain from one season to another".

Nonetheless, taking the jab twice a year is generally safe too. Common side effects, such as soreness at the injection site or low-grade fever, remain the same.

"There are no known harmful cumulative effects from taking it twice a year," she added.

The CDA spokeswoman said the Expert Committee on Immunisation (ECI) recommends high-risk groups to be vaccinated at least once a year. This refers to those aged six months to five years, 65 years and above, as well as those aged six to 64 years with certain medical conditions.

If there is substantial change to the upcoming vaccine, the ECI also recommends they receive an additional dose of the updated vaccine.

Q: Why are those aged 65 and above, and between six months and five years, recommended for the vaccine regardless of underlying conditions?

Prof Oon said they are more vulnerable to flu-related complications, which could be as severe as pneumonia, meningitis, or infection of the lungs, nasal passages or ear.

Seniors often have weaker immune responses or underlying medical conditions, which could increase their risk of severe illness, or even death, from influenza, she said.

Younger children have immune systems that have yet to mature, increasing their likelihood to develop serious complications.

Q: It is sometimes difficult to book an appointment through the apps at the polyclinics. Is there a shortage of vaccines?

Checks by The Straits Times found that it could be difficult to book appointments through the HealthHub app, or the various healthcare clusters' individual apps, compared with bookings at GP clinics or retail pharmacies.

For instance, in early September, some apps showed available slots only from December onwards.

Checks on Oct 8 showed that Queenstown Polyclinic had an available slot on only Oct 30 but no slots in November. Outram, Pasir Ris and Tampines North polyclinics had no slots for the entire month of October.

All three polyclinic clusters clarified there is no shortage of vaccines, but sometimes most slots have been taken up, with some people booking from as far back as a year ago.

Q: What can I do if I cannot get a slot at the polyclinic?

The national HealthHub app offers a common platform to make appointments at any polyclinic for flu vaccination.

In addition, each cluster has its own app for bookings, and slots may open up when earlier bookings are cancelled.

All clusters also provide a hotline for the public to call for appointment bookings:

• For SingHealth Polyclinics in the east, the hotline is 6643-6969
• For NHG Polyclinics in the central and north, the hotline is 6355-3000
• For National University Polyclinics in the west, the hotline is 6908-2222

Appointments at GP clinics can be made through the Health Appointment System, which has information on subsidies for eligible Singaporeans.