What is influenza vaccine?

Definition

The influenza vaccine helps to protect against infection with the influenza virus.
Influenza is an acute viral respiratory illness with abrupt
onset and is spread primarily by respiratory droplets from person to person
(mainly through inhalation of virus-containing droplets). Influenza is caused by a
group of viruses of the Orthomyxoviridae family, which are separated into three
strain types (A, B, and C) according to their nuclear material.

Vaccination is the most effective protection against influenza. It is recommended for unhealthy persons and for persons who are likely to transmit influenza to unhealthy persons in a given community. Moreover, the vaccine may be administered to anyone wishing to reduce the risk of influenza.

Influenza vaccines are designed to trigger an immune response to
hemagglutinin and neuraminidase, the two proteins found
on the surface of the influenza virus. These proteins are always changing
(mutating), so every year, seasonal influenza vaccines have to be reformulated
with the three strains that are likely to be more effective in fighting new
influenza strains.

The World
Health Organization’s Global Influenza Programme monitors the influenza viruses circulating
among humans worldwide and quickly identifies new strains so that new, appropriate
vaccines can be made for a particular year.

Types of Influenza Vaccines

The trivalent inactivated influenza vaccine (TIV) has been available since the mid-twentieth century. TIV is administered by intramuscular or intradermal routes and contains three inactivated viruses: type A (H1N1), type A (H3N2), and type B. The influenza vaccine viruses are grown in chicken egg, thus the final product contains residual egg protein. The vaccines are also available in both pediatric- and adult-dose formulations and can be preservative-free in a single vial or in a multidose vial with thimerosal as a preservative.

The live attenuated influenza vaccine (LAIV), which contains the same three influenza viruses as TIV, is administered by intranasal route. LAIV viruses are also grown in chicken egg. LAIV is preservative-free and is provided in a single-dose sprayer unit with one-half the dosage sprayed into each nostril.

Improved technology and innovation has enabled improved methods of administering influenza vaccines, including a reduced-dose injectable made possible by the addition of adjuvants, and the use of a cell culture vaccine. Scientists are also exploring new routes of administration, such as intradermal (with or without needle) and transcutaneous, in which a patch delivers the vaccine through micro-needles that may barely penetrate the skin before dissolving and releasing the vaccine.

Most vaccinated persons develop postvaccination hemagglutination inhibition
antibody titers. These antibodies are protective against
illness caused by strains similar to those in the vaccine or by related variants
that may emerge during outbreaks.

Amidst debates over the effectiveness and necessity of vaccinations, concern had also always existed over the high number of elderly adults who would still succumb to influenza and possibly lose their lives despite having been vaccinated because of their naturally weaker immune systems. Therefore, in late 2015, the US Food and Drug Administration (FDA) approved an influenza vaccine booster that had previously been in use in several other countries. The vaccine with the adjuvant, which helps stimulate the immune system to make the vaccine more effective, is known as Fluad and was expected to be available in the United States in 2016. Additionally, scientists were continuing to experiment on whether a universal vaccine could be produced that would help the immune system fight groups of viruses rather than a specific strain.

Bibliography

Betts, R. F. “Influenza Virus.” In Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. Ed. Gerald L. Mandell, John E. Bennett, and Raphael Dolin. 7th ed. New York: Churchill, 2010. Print.

Delves, Peter J., et al. Roitt’s Essential Immunology. 11th ed. Malden: Blackwell, 2006. Print.

Fox, Maggie. "Fluad: Food and Drug Administration Approves a New, Boosted Flu Vaccine." NBC News. NBCNews.com, 30 Nov. 2015. Web. 30 Dec. 2015.

Hak, E., et al. “Influence of High-Risk Medical Conditions on the Effectiveness of Influenza Vaccination Among Elderly Members of Three Large Managed-Care Organizations.” Clinical Infectious Diseases 35 (2002): 370–77. Print.

Plotkin, Stanley A., Walter A. Orenstein, and Paul A. Offit. Vaccines. 5th ed. Philadelphia: Saunders, 2008. Print.

Zhang, Sarah. "Scientists Get One Step Closer to a Universal Flu Vaccine." Wired. Condé Nast, 24 Aug. 2015. Web. 30 Dec. 2015.