With winter nearly upon us, many are considering whether they should have the flu jab.
While some dismiss the viral infection as just a runny nose, flu can leave sufferers bedridden, as well as causing serious complications among children, the elderly and pregnant women.
To help you stay well for the rest of the year and into 2020, Yahoo UK looks at who should get the vaccine.
The flu vaccine stimulates the immune system to produce proteins, called antibodies, that fight against the virus.
If someone is exposed to the virus after having the jab, their immune system will recognise the pathogen and immediately make antibodies to destroy it.
It can take up to two weeks for the immune system to produce these “back up” antibodies. It is therefore important to have the vaccine several weeks before flu season strikes.
The NHS recommends getting vaccinated in October or November, ahead of the peak of the virus’ activity between December and February.
Flu viruses tend to mutate to avoid people developing resistance to them. As a result, it is important to have the jab before every new season.
At the start of the year, the World Health Organization predicts which strains are most likely to be circulating the following winter. It then recommends vaccine manufacturers make jabs that protect against these strains.
The vaccines are usually available in the UK from September.
Studies have shown the flu vaccine works. However, it is possible to catch a strain not included in the jab. Immunised people may therefore still get ill, however, this is likely to be milder than if they had not had the jab in the first place, according to the NHS.
Who is eligible for a free flu jab?
The elderly, pregnant women, children, healthcare workers and people with certain medical conditions are all eligible for a free flu vaccine on the NHS. Research suggests these groups are more at risk of serious flu complications, like pneumonia.
Jabs can be administered at a GP surgery or pharmacy that offers the service. Midwifery services are also available for pregnant women.
Pregnant women should have the jab no matter what trimester they are in. Evidence suggests catching the virus while expecting raises a mother-to-be’s risk of the chest infection bronchitis, which can develop into pneumonia.
Battling flu while pregnant also raises the risk the baby will be premature or a low birthweight. In severe cases, it can even lead to a stillbirth.
Pregnant women who have the flu jab also pass some of the protection onto their baby, which lasts for the first few months of their life.
As well as pregnant women, children who were aged between two and three on August 31 last year or those in primary school will usually be offered a nasal spray vaccine.
The jab is also given to youngsters aged between six months and two years old with a long-term health condition.
Also eligible for free immunisation are those with chronic health conditions, like diabetes, asthma and heart failure.
Among the elderly, those who will be 65 or over on March 31 next year should claim their free jab.
Flu is rarely serious among healthy adults, however, it can cause unpleasant symptoms like a sudden fever, exhaustion and loss of appetite.
Getting vaccinated also protects those around you. The flu virus is contagious and can spread through coughing, sneezing or touching contaminated surfaces, according to Boots.
Despite its benefits, many are put off the flu jab over the misleading myth the vaccine itself infects people with the virus.
The flu vaccine is made up of inactivated viruses, which cannot cause infection, according to the NHS.
Some complain of a sore arm at the site of the injection, while others report a slight fever or aching muscles in the following days. Other side effects, like allergic reactions, are rare.
Flu vaccines licensed in the UK are thoroughly tested before they are made available and have a good safety record, the NHS states.