Inactivated influenza vaccines, mainly split virus vaccines and subunit vaccines are currently used to prevent Influenza. Split virus vaccines are produced by disrupting the virus by a detergent. Subunit vaccines are more effective in generating immune response and are produced by advanced purification of HA and NA viral envelope proteins omitting other viral components. The current trivalent inactivated influenza vaccines contain the two Influenza virus A subtypes H3N2 and H1N1 and one type B virus. These vaccines protect against swine flu also. Standard dose trivalent shots (IIV3) are manufactured by using virus grown in eggs. These are licensed to use for persons of age 6 months and older. Trivalent shots are available under different brand names. Influenza vaccines offer about 70–90% protection against clinical disease in healthy adults when the vaccine antigens and circulating viruses match properly.
Why is prevention by vaccine better than treatment with available antiviral medicines?
Antiviral drugs such as Amantadine, Rimantadine, Zanamivir and Oseltamivir are available to ease the symptoms of flu. Emergence of mutant viral strains that are resistant to these drugs have made it difficult to treat the influenza infections. High cost, daily dosage, occasional side effects and limited availability of antiviral drugs during major outbreaks are other existing concerns. Prevention by yearly vaccine shots seems to be the only wise way to combat influenza.
How is influenza vaccine administered?
TIVs are given as a shot in the deltoid muscle in person >1 year of age and in the anterolateral aspect of thigh in persons between 6-12 months of age. Children below 3 years of age should receive half the amount of the dose given to adults.
Recommended Schedule for inactivated (TIV) trivalent influenza vaccine:
- Minimum age is 6 months
- 2 doses at 4 week interval for the first time vaccination in children 6 months to 9 years of age
- Single dose every year in young children in the age group 1-9 years
- Single dose every year in older children and adults recommended only for persons with high risk medical conditions
Soreness, redness or inflammation at the site where the shot is given. Low grade fever and body aches can occur following the flu shot.
Marketed Influenza Products
Here is the list of WHO pre-qualified vaccine products available in market. Click on name of the product to know more.