Products
Influenza vaccines are commercially available as injectables from a variety of suppliers in many countries.
Structure and properties
Vaccines licensed in many countries contain inactivated influenza virus surface antigens, hemagglutinin and neuraminidase, according to annual WHO recommendations. Since the viruses change slightly on an ongoing basis, continuous adaptation is necessary. The vaccines are so-called trivalent, i.e. they consist of the proteins of three strains, two of type A and one of type B. Influenza vaccines are usually derived from fertilized chicken eggs and are inactivated. Cell-based systems for production also exist.
Effects
Influenza vaccination (ATC J07BB02) triggers the production of antibodies to influenza viruses that neutralize the viruses of the appropriate strains, thereby preventing or attenuating infection. The effect is delayed within 2 to 4 weeks and lasts between 4 to 12 months (optimal protection about 4 months). A well-known critic of the vaccination, the epidemiologist Tom Jefferson, criticizes in several Cochrane reviews that the effectiveness is scientifically insufficiently proven and that the vaccination protects mainly healthy adults reasonably well. The effectiveness is insufficient especially in the risk groups, i.e. in children and the elderly. It should be noted that there is no complete protection and vaccination does not protect against the numerous colds. Various factors influence the immune response, including age, immunosuppression, and the dosage form. In addition, vaccination does not always contain the correct viral strains that cause the current wave of influenza.
Indications
For active immunization against influenza, according to the recommendations of the Federal Office of Public Health (FOPH). Risk and target groups for whom vaccination is recommended by authorities include the elderly aged 65 years and older, people with underlying diseases, premature infants, contact persons, and medical and nursing personnel.
Dosage
According to the drug label. Drugs are administered intramuscularly into the upper arm muscle (deltoid muscle). Some may also be injected deeply subcutaneously; others may be injected exclusively intramuscularly. Do not administer intravenously under any circumstances! According to the FOPH, the optimal time period for administration is mid-October to mid-November.
Contraindications
- Hypersensitivity to the various components contained (depending on the manufacturer, including viral components, ovalbumin/chicken egg white, kanamycin, neomycin, gentamicin, formaldehyde, cetyltrimethylammonium bromide, polysorbate 80, sodium deoxycholate).
- Acute, severe, febrile illnesses.
Appropriate medical treatment and monitoring must be available if a severe hypersensitivity reaction occurs. Full details of precautions and interactions can be found in the drug label.
Adverse Effects
Possible adverse effects include injection site reactions such as pain, swelling, redness, and induration. General symptoms such as fatigue, weakness, feeling sick, fever, muscle aches, diarrhea, headache, dizziness, rhinitis, and pharyngitis are common. Other side effects include chills, nausea, lower abdominal pain, and joint pain. These symptoms usually disappear within a few days. Rarely, allergic reactions or temporary blood count disorders (thrombocytopenia) may occur after vaccination. Extremely rarely, neurological reactions have been reported (Guillain-Barré syndrome).
Influenza vaccination and anaphylaxis.
A dangerous and potentially life-threatening complication during vaccination is severe hypersensitivity reactions such as anaphylaxis. It manifests, for example, in symptoms such as shortness of breath, wheezing, low blood pressure, palpitations, hives, and swelling. Possible differential diagnoses include anaphylactoid reactions and vasovagal reactions caused by excitement associated with vaccination. Possible antigens include all components of the production process that are still present in the finished product. In addition to the virus components, these include chicken egg protein, antibiotics and excipients (see above). A proven allergy does not necessarily lead to anaphylaxis, but is a contraindication according to the drug information leaflet.Anaphylactic reactions are generally extremely rare after vaccinations. In the literature, for example, the figure of 0.65 to 1.5 cases per 1 million vaccine doses in children and adolescents is cited (Bohlke et al., 2003). In another publication, a rate of 0.002% is reported for influenza vaccination (Coop et al., 2007). Nevertheless, it is recommended to observe the vaccinated for 15-20 minutes because most severe cases occur during this period. Standard treatment of anaphylaxis is considered to be the administration of epinephrine. Depending on the leading symptoms, anti-allergic drugs such as antihistamines and glucocorticoids are also used, as well as beta2-sympathomimetics, oxygen and intravenous fluids. In severe cases, intubation may be indicated.
