The influenza vaccine is given as injections in October. After vaccination, it will take up to three weeks before it offers protection. It lasts for six to 12 months and therefore only works for one season.
The World Health Organization WHO decides which influenza strains are to be included in the year's influenza vaccine. As part of its influenza activities, the WHO monitors the progression of the disease on the southern hemisphere whose influenza season staggers the influenza season in Denmark by six months.
Based on knowledge from last year's influenza strains and ongoing reports on the spread of influenza from health authorities worldwide, the WHO experts decide which influenza strains should make up the current year's vaccine composition. This takes place in spring, six months in advance of its expected use, to make sure it is ready in time.
But even if you have received the vaccine, you can still catch influenza. It could happen if your body has not produced enough antibodies, but also if viruses emerge that the WHO did not predict.
If you catch influenza in September, there is no need for you to be vaccinated later that season, because your body will produce antibodies by itself.
At the Danish Health and Medicines Authority, we follow the global collaboration on influenza viruses. We have particular focus on any possible side effects connected to the new vaccines that enter the market. You can read more about this under news about side effects.
Influenza vaccines, season 2012/2013
The vaccines contain the must current influenza strains of the three seasonal influenza viruses in global circulation:
- A/California/7/2009 (H1N1)-like virus (2009 pandemic virus)
- A/Victoria/361/2011 (H3N2)-like virus
- B/Wisconsin/1/2010-like virus
The vaccines meet the WHO recommendations for the Northern hemisphere for the 2012/2013 season.
If you do not belong to a group that is particularly vulnerable to influenza, there is no need to be worried about influenza.
If you are infected with influenza virus, you will normally fall ill after one to three days. Normally, the body will fight the flu virus by itself, and even though the flu causes a lot of discomfort, people who are otherwise in good health will cure themselves without major difficulty.
But if you have a disease that makes you more vulnerable to the flu than others, your doctor can prescribe you an antiviral medicine. Antiviral medicines inhibit growth of the flu virus and shorten the duration of illness by a day or two. This could be relevant for persons whose disease has made them so weak they cannot tolerate a high fever or other complications that last for several days. If you have a lung condition, it is a good idea to consult your doctor if you have been exposed to infection. Also see: Particularly vulnerable groups should choose to be vaccinated.
Once the flu breaks out, the level of virus particles in the body increases drastically during the first 48 hours, and it is important to start treatment in this period to produce the intended effect. The most commonly used antiviral medicines against influenza are Tamiflu® and Relenza®. Antiviral medicines are prescription drugs.