The Influenza Virus & Vaccine Efficacy
Bryant & Stratton College
6 November 2014
Why is the flu vaccine so controversial? There always seems to be two strong, opposing sides in terms of its efficacy or safety, separated by innumerable studies that range from black and white, to grey area conclusions. Worldwide, the influenza virus is often associated with serious health events, and immunizations are considered a key component in preventing a majority of these consequences. With this year’s flu season in full swing, the influenza vaccine is available in nearly every pharmacy, hospital, and clinic, yet many people wonder if ...view middle of the document...
The incubation period outside of the body is short, about 18-72 hours, and up to 24-48 hours after symptoms start when in the body (Hunt, 2010, Pathogenesis, p. 2).
The flu viruses are constantly changing their virology factors, making vaccines difficult to cover all strains from year to year, or even in one season/person. There are two main ways that the virus can adapt and change. One way is called “antigenic drift”, which are small genetic changes that produce a new virus that is closely related and mostly share the same antigenic properties, so the body’s immune system will usually recognize it and respond (sometimes called cross-protection) (CDC, 2014, How the flu virus can change, p. 1). Over time, however, these changes can cause the virus to branch far enough from the original virus’s genetic makeup, and become different enough that the body cannot recognize the new virus, and the manufactured antibodies are no longer effective. After an infected person develops antibodies against the specific virus, the virus undergoes antigenic drift, and accumulates enough antigenic changes that the original antibodies created are no longer effective in destroying the virus, which is why a person can get the flu more than once, and why the vaccine needs to be reviewed and updated every year (CDC, 2014, How the flu virus can change, p. 3). The other way that the influenza virus changes is called “antigenic shift”, which is marked by a major and abrupt antigenic shift in the type A viruses, which results in a new hemagglutinin protein that infects humans (Balgopal, 2011, Antigenic shift, p 1-3). This process occurs when two or more strains of different viruses combine to form a new subtype, and possess a mixture of surface antigens. There are three types of antigenic shift, which allows for a higher diversity of adaptation. It can occur when a) an intermediate host is infected with two different types of an influenza A strain, and they form a new strain, b) without an intermediate host, a strain jumps directly from one host to another through body fluids, allowing direct contact, or c) it does not undergo genetic change, but jumps from host to an intermediate host, then to a new host (Balgopal, 2011, Antigenic shift p 3).
Worldwide, the influenza virus is often associated with serious health events, ranging from minor impairments in uncomplicated influenza, such as fever, headaches, aches, a cough and runny nose, and sometimes GI issues, to severe complications in cases of more involved pulmonary cases, such as croup, pneumonia, and can cause a person to be hospitalized, or can cause death in elderly individuals. Immunizations are considered a key component in preventing a majority of these consequences, and with this year’s flu season just around the corner, and the influenza vaccine starting to become available nearly everywhere, many people wonder if the flu shot is a good choice for them. According to the Center for...