Influenza vaccine

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Influenza vaccine
FLUBLOK® FDA Package Insert
Clinical Pharmacology
Indications and Usage
Warnings and Precautions
Adverse Reactions
Clinical Studies
Dosage and Administration
How Supplied
Labels and Packages

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohamed Moubarak, M.D. [2]


The Influenza vaccine or flu shot is a vaccine to protect against the highly variable influenza virus.

The annual flu kills an estimated 36,000 people in the United States. The annually updated trivalent flu vaccine for the 2007–2008 season consists of hemagglutinin (HA) surface glycoprotein components from influenza H3N2, H1N1, and B influenza viruses.[1]

Each year the influenza virus changes and different strains become dominant. Due to the high mutability of the virus a particular vaccine formulation usually works for only about a year. The World Health Organization coordinates the contents of the vaccine each year to contain the most likely strains of the virus to attack the next year. The flu vaccine is usually recommended for anyone in a high-risk group who would be likely to suffer complications from influenza.

Inactivated influenza vaccine (IIV) Live attenuated


Mammalian cells Recombinant (RIV)† Embryonated chicken eggs Normal
Trivalent Trivalent Quadrivalent Trivalent Quadrivalent Quadrivalent
High dose * Fluzone high-dose.
CDC lists as an option for age > 65 years old[2]
Standard dose Flucelvax FluBlok Flublok Quadrivalent
(has 45 μg of hemagglutinin per strain)
Fluzone Fluzone Quadrivalent
Low dose Fluzone Intradermal Quadrivalent‡
* High dose indicates 60 mcg of each hemagglutinin antigen. Standard dose contains 15 mcg[3]
† Contains only hemagglutinin antigens
‡ Needle-free jet for needle phobia



US Brand Names


FDA Package Insert

Description | Clinical Pharmacology | Indications and Usage | Contraindications | Warnings and Precautions | Adverse Reactions | Dosage and Administration | How Supplied | Labels and Packages

Mechanism of Action

Flublok contains recombinant HA proteins of the three strains of influenza virus specified by health authorities for inclusion in the annual seasonal vaccine. These proteins function as antigens which induce a humoral immune response, measured by hemagglutinin inhibition antibody (HAI).

Antibodies against one influenza virus type or subtype confer limited or no protection against another. Furthermore, antibodies to one antigenic variant of influenza virus might not protect against a new antigenic variant of the same type or subtype. Frequent development of antigenic variants through antigenic drift is the virologic basis for seasonal epidemics and the reason for the usual replacement of one or more influenza virus strains in each year's influenza vaccine. Therefore, influenza vaccines are standardized to contain the hemagglutinins of influenza virus strains (i.e., typically two type A and one type B), representing the influenza viruses likely to be circulating in the U.S. in the upcoming winter.


  1. CDC Flu Vaccine Composition 07/08
  2. Grohskopf LA, Sokolow LZ, Broder KR, Olsen SJ, Karron RA, Jernigan DB; et al. (2016). "Prevention and Control of Seasonal Influenza with Vaccines". MMWR Recomm Rep. 65 (5): 1–54. doi:10.15585/mmwr.rr6505a1. PMID 27560619.
  3. Centers for Disease Control and Prevention (CDC) (2010). "Licensure of a -dose inactivated influenza vaccine for persons aged >or=65 years (Fluzone -Dose) and guidance for use - United States, 2010". MMWR Morb Mortal Wkly Rep. 59 (16): 485–6. PMID 20431524.