Next to clean water, humankind's most important innovation is developing vaccines that prevent people from contracting a specific disease.
Dr Leong Hoe Nam, an infectious diseases specialist at Mount Elizabeth Novena Hospital, says vaccines have also prevented the spread of diseases to others.
He said: "Infections are prevalent all over the world and global inter- connectedness brings life- threatening infections right to Singapore's doorstep."
Infections that caused the 2003 Sars and 2009 H1N1 flu pandemics were imported here.
In May this year, a 48-year-old man who returned from Brazil tested positive for Zika, making him the first confirmed case of the mosquito-borne virus in Singapore.
To date, however, Zika has not spread in Singapore. There is no vaccine for it.
Most people associate vaccinations with immunising children against dangerous childhood diseases but they should also think about vaccines when they are planning to travel.
The type of vaccines to get would depend on the country one is visiting and the kind of activities being undertaken.
For example, travellers should get a yellow fever vaccine when going to countries endemic with yellow fever, and Japanese encephalitis vaccine in South-east Asian or East Asian countries, especially in rural areas that have pig farming.
But the influenza vaccine is "not a travel vaccine" and should be given at least once a year, Dr Leong stressed.
He warned that influenza exists in Singapore throughout the year, killing the elderly and people with compromised immune systems because of illness.
A vaccine contains a weakened form of the germ, which trains the body to fight it.
It could be in the form of a live but weakened version of the virus (such as the chickenpox vaccine) or a chopped-up version of the virus (with only a few bacterial proteins that will elicit a vaccine response).
Either of these can train the body before the infection occurs, offering protection to the individual.
When the real infection occurs, the body, having had previous training, would respond suitably and adequately, he added.
Here are 10 things you should know about getting vaccinated against influenza:
1 Influenza is an acute viral infection caused by a number of influenza viruses.
2 Influenza is not a common cold. People with a cold will suffer from a runny or stuffy nose, but it generally does not result in serious health problems such as pneumonia, bacterial infections or hospitalisation.
Influenza gives rise to symptoms such as fever, chills, headache, fatigue, muscle pain, cough (usually non-productive), runny or stuffy nose and sore throat.
3 In Singapore, two influenza A viruses and two influenza B viruses have been the main viruses in circulation, with influenza B representing up to 70 per cent of all circulating strains in the first quarter of this year.
4 Influenza has two peaks in a year, between April and August and between November and February.
5 The influenza vaccine can protect those who are more vulnerable to complications.
This includes people aged 65 and above, pregnant women, children (six months to five years), people of any age with certain medical conditions, such as chronic heart, lung, kidney, liver, blood or metabolic diseases (such as diabetes), and residents of nursing homes and intermediate- and long-term care facilities.
6 While one region of the world may have an outbreak with one strain of influenza B - Yamagata, another region would have influenza B of another strain - Victoria.
7 For many years, the World Health Organisation (WHO) has updated its recommendation on vaccine composition biannually that targets the three (trivalent) most representative virus types in circulation (two sub-types of influenza A viruses and one B virus).
8 Almost everyone would be in close contact with someone who has a chronic medical condition.
The Centres for Disease Control and Prevention (CDC) in Atlanta, the United States, and the Singa- pore Clinical Practice Guidelines on Adult Vaccinations recommend influenza vaccination for every-one.
The additional advantage of vaccination is that herd immunity in the community improves, resulting in even better protection from influenza.
9 Since 2013, quadrivalent vaccine composition with a second influenza B virus has been recommended by the WHO.
The quadrivalent vaccine is designed to protect against four different influenza viruses which are prevailing - two influenza A viruses (H1N1 and H3N2) and two influenza B viruses (for example, the Yamagata and Victoria strains).
This is believed to lead to an 80 per cent reduction of influenza B- related cases, hospitalisation and deaths.
10 There are two types of quadrivalent influenza vaccines in Singapore:
•FluQuadri by Sanofi Pasteur is licensed for use in patients as young as six months old.
•Fluarix Quadrivalent by GlaxoSmithKlineis approved for children (three years and older) and adults.