Influenza (flu) vaccination for older adults

This fact box will help you to weigh the benefits and harms of the influenza vaccination for older adults. The information and numbers are based on the best scientific evidence currently available.

This fact box was developed by the Harding Center for Risk Literacy.

What is influenza (flu)?

Influenza is a disease caused by an influenza virus. The accompanying symptoms are high fever, headache, back pain, and aching limbs as well as a cough, runny nose, sore throat, and hoarseness. People often talk about having influenza without being tested for it. Influenza-like-illnesses involve influenza as well as other respiratory diseases which cause influenza-like-symptoms (high fever, cough), so that physicians cannot distinguish between them without a laboratory test.

Influenza can be transmitted through contaminated objects (e.g. door handles) or spread in the air as aerosol particles when an infected person sneezes, coughs, or spits [1].

Of 70,247 confirmed cases during the flu season 2014/2015 in Germany, the age group of 35- to 59-year-olds was most heavily affected, followed by those older than 60 [2].

What is an influenza vaccination?

An influenza vaccination is designed to prevent the infection and illness caused by flu viruses.

 

Who might consider a vaccination?

Adults aged 60 years or older [1].

What are alternative prevention options?

Good personal hygiene habits, such as frequent hand washing (especially before and after contact with people at risk) and disinfection of potentially contaminated surfaces and objects (e.g. door handles) may prevent an infection. In addition, keeping away from people with influenza symptoms and maintaining a healthy lifestyle (e.g. balanced diet, exercise) may reduce the risk of an infection [1].

Fact box influenza (flu) vaccination for older adults
Fact box influenza (flu) vaccination for older adults © Harding Center for Risk Literacy
What does the fact box show?

The fact box shows the benefits and harms of the influenza vaccination for adults aged 60 or older compared to a placebo vaccination.

The table may be read as follows:

Within one year, between 42 and 128 of every 1,000 older adults treated with a placebo injection suffered from confirmed cases of influenza. In comparison, between 17 and 45 of every 1,000 older adults who received an influenza vaccination suffered from confirmed cases of influenza.

The numbers in the fact box are rounded. The numbers for cases of influenza and influenza-like infections are taken from two randomized studies with 2,000 participants aged 60 and older. The numbers for mortality derive from four cohort studies with more than 300,000 people over 56 years of age. These studies included healthy und unhealthy older adults in different years, with fundamental differences in the frequency of infection and the regions in which influenza spread.

The numbers for arm pain are taken from four randomized controlled studies with 2,500 participants. The numbers for local side-effects are from two randomized controlled studies with a total of 1,800 participants [3, 4, 5].

What other aspects should be considered?

The variation in the effectiveness of the influenza vaccination depends on where and how severely the virus spreads and on how well the seasonal vaccine matches the circulating strains. Because the virus varies each year, an annual vaccination is necessary.

Between 4 and 17 out of every 1,000 older adults with placebo injections were hospitalized due to influenza-like illnesses or pneumonia. In comparison, between 3 and 13 out of every 1,000 older adults with influenza vaccinations were hospitalized due to influenza-like illnesses or pneumonia.

The influenza vaccination does not protect from other infections or illnesses that cause influenza-like symptoms.

Do the results provide proof (evidence) for the benefits and harms of the vaccination?

Overall, the evidence is of low and sometimes of moderate quality. Only a small number of randomized controlled studies exist. Additionally, because the vaccination’s effectiveness is limited to a year, the informative value of these studies regarding its general effectiveness over a longer period of time is significantly reduced.

Version history of the fact box
  • August 2016 (last update)
Scources

Information within the fact box were obtained from the following sources:

Information about symptoms, the risk of infection and the progress of disease in case of a infection:

[1] Robert Koch-Institut. RKI-Ratgeber für Ärzte: Influenza (Teil 1): Erkrankungen durch saisonale Influenzaviren. 2016; https://www.rki.de/DE/Content/Infekt/EpidBull/Merkblaetter/Ratgeber_Influenza_saisonal.html, access date 24 Aug 2016.

Epidemiological figures for the influenza season 2014/2015:

[2] Buda S, Köpke K, Prahm K et al. Bericht zur Epidemiologie der Influenza in Deutschland Saison 2014/2015. Robert Koch-Institut (Ed.). ISBN: 978-3-89606-265-9; https://edoc.rki.de/handle/176904/3562, Access date 24 Aug 2016.

Numbers about benefits and harms:

Numbers about benefits are from randomised controlled trials with about 9.200 (influenza-like-illness), 24.200 (confirmed influenza disease) and 1.100 (physician contact) participants.

Numbers about harms are from randomised controlled trials with about 12.800 (muscle pain), 9.000 (fever), 11.300 (feeling unwell) and 13.200 (headache) participants.

[3] Demicheli V, Jefferson T, Al-Ansary LA et al. Vaccines for preventing influenza in healthy adults. Cochrane Database of Systematic Reviews 2014; 3:CD001269.