Flu vaccination
The composition of the vaccine is reviewed and updated every year as the flu virus is constantly changing. Considerations include which flu viruses are causing illness, the rate at which the viruses are spreading, and how well last season's vaccine protects against those viruses. The quadrivalent vaccine contains four inactivated viruses: type A(H1N1), type A(H3N2) and two types B. The start of giving the vaccine is the end of September and the beginning of October until the end of May of the following year. According to WHO recommendations, all persons from the age of 6 months should receive the flu vaccine, regardless of their health status.
Risk groups:
Children over 6 months old with weakened immunity, people aged 65 and over, people with chronic disorders (pulmonary or cardiovascular, renal, hepatic, neurological, hematological or metabolic disorders), people with compromised immunity, pregnant women, people of age 6 months to 18 years of age who take aspirin or medications containing salicylates and who may be at risk of experiencing Reye's syndrome after influenza virus infection, nursing home staff, people with extreme obesity (body mass index is 40 or older), professional and support staff in health facilities, family contacts and caregivers of children under 5 and adults aged 65 and over, and family contacts and caregivers of people with medical conditions that put them at risk added for severe illness from influenza.
Vaccination schedule and it`s use
The flu can start in early October and last until the end of April or May, but most often peaks in January. To ensure maximum protection, vaccination should be given before the flu begins to spread in the community. The flu vaccine is given by intramuscular injection and can be given on the same day or at any time before or after other inactivated vaccines or live vaccines..
Immunogenicity and vaccine efficacy
For practical purposes, the duration of immunity after influenza vaccination is less than a year due to vaccine-induced antibody attenuation and antigenic drift of circulating influenza viruses. The effectiveness of the flu vaccine depends on many factors including the similarity of the vaccine strains to circulating strains, the age and health status of the recipient, and the type of vaccine administered. Vaccination is effective in reducing the risk of influenza illness by 40% to 60% in the general population when the vaccine strains and circulating viruses are similar. However, the vaccine may be less effective in preventing disease in people over 65. Studies have demonstrated a number of benefits from flu vaccination, including less: illness, medical visits, hospitalizations. Flu vaccination has also been associated with positive outcomes for people with chronic health conditions and pregnant women.
Contraindications and precautions to vaccination
A history of severe allergic reactions (anaphylaxis) to a vaccine component or after a previous dose is a contraindication for further doses. Acute moderate or severe illness (with or without fever) is considered a precaution against vaccination, although persons with mild illness may be vaccinated. History of Guillain-Barré syndrome within 6 weeks of receiving influenza vaccine is a precaution against influenza vaccination.
Vaccine safety
Studies support the safety of annual vaccination in children and adults. Mild reactions are common side reactions. These include pain, redness, swelling at the injection site. These reactions are transient, usually lasting 1 to 2 days. Nonspecific systemic symptoms, including fever, chills, and myalgia, occur less frequently. These symptoms usually occur in those who have not previously been exposed to the viral antigens in the vaccine. Symptoms usually occur within 6 to 12 hours after vaccination and last 1 to 2 days.
Vaccination during pregnancy
Pregnant women are at increased risk for severe illness and complications from the flu due to changes in immunological, heart and lung function. In addition, some studies suggest that influenza infection is associated with premature birth and fetal death. Vaccination can be done at any time during pregnancy, before and during the flu season.
Vaccine storage and handling
Influenza vaccines should be stored between 2°C and 8°C.