Flu Vaccine Pros And Cons

The influenza vaccine, also known as flu shot, is an annual vaccination using a vaccine that is specific for a given year to protect against the highly variable influenza virus. Each seasonal influenza vaccine contains antigens representing three or four influenza virus strains: one influenza type A subtype H1N1 virus strain, one influenza type A subtype H3N2 virus strain, and either one or two influenza type B virus strains. Influenza vaccines may be administered as an injection or as a nasal spray.

The U.S. Centers for Disease Control and Prevention recommend that everyone over the ages of 6 months should receive the seasonal influenza vaccine. Vaccination campaigns usually focus on people who are at high risk of serious complications

if they catch the flu, such as the elderly and people living with chronic illness or those with weakened immune systems, as well as health care workers.
Most flu vaccines provide modest protection against contracting influenza, with the effect seasonably variable depending on antigenic drift. Some studies have concluded that there is little evidence for efficacy among the elderly, while others concluded that efficacy ranges from "acceptable" to "high" depending on the specific vaccine formulation.
Medical uses
According to the Centers for Disease Control and Prevention, the flu vaccine is the best way to protect people against the flu and prevent its spread.

The flu vaccine can also reduce the severity of the flu if a person contracts a strain of the flu that the vaccine did not contain. It takes about two weeks following vaccination for antibodies to protect against the flu.

A 2012 meta analysis found that flu shots were efficacious 67 percent of the time; the populations that benefited the most were HIV-positive adults ages 18 to 55, healthy adults ages 18 to 46 and healthy children ages 6 to 24 months .

Effectiveness

A vaccine is assessed by its efficacy; the extent to which it reduces risk of disease under controlled conditions, and its effectiveness, the observed reduction in risk after the vaccine is put into use. In the case of influenza, effectiveness is expected to be lower than the efficacy because it is measured using the rates of influenza-like illness, which is not always caused by influenza. However, studies on the effectiveness of flu vaccines in the real world are difficult; vaccines may be imperfectly matched, virus prevalence varies widely between years, and influenza is often confused with other influenza-like illnesses. However, in most years, the flu vaccine strains have been a good match for the circulating strains, and even a mis-matched vaccine can often provide

cross-protection.
Trials of both live and inactivated influenza vaccines against seasonal influenza have been summarized in several 2012 meta-analyses.

Studies on live vaccines have very limited data, but these preparations may be more effective than inactivated vaccines. The meta-analyses examined the efficacy and effectiveness of inactivated vaccines against seasonal influenza in adults, and the elderly.

A different approach is where Internet content is used to estimate the impact of an influenza vaccination campaign. More specifically, researchers have used data from Twitter and Bing, and proposed a statistical framework which, after a series of operations, maps this information to estimates of the percentage of of influenza-like illness in areas, where vaccinations have been performed. Their impact estimates were in accordance with estimations from Public Health England.

Children
The CDC recommend that everyone except children under the age of six months should receive the seasonal influenza vaccine. Of these eighteen HCW studies, only two also assessed the relationship of patient mortality relative to staff influenza vaccine uptake; both found that higher rates of health care worker vaccination correlated with reduced patient deaths.
Elderly
Evidence for an effect in adults over 65 years old is unclear. Reviews of randomized controlled and observational studies have found a lack of high quality evidence. Reviews of case control studies have found effects against laboratory-confirmed influenza, pneumonia, and death among the community-dwelling elderly.
The group most vulnerable to non-pandemic flu, the elderly, benefits least from the vaccine. There are multiple reasons behind this steep decline in vaccine efficacy, the most common of which are the declining immunological function and frailty associated with advanced age. In a non-pandemic year, a person in the United States aged 50–64 is nearly ten times more likely to die an influenza-associated death than a younger person, and a person over age 65 is over ten times more likely to die an influenza-associated death than the 50–64 age group.
. Furthermore, the side effects and risks of inoculation are mild and temporary when compared to the risks and severe health effects of the annual influenza epidemic's well-documented toll of illness, hospitalization, and death.
Flu vaccination may lead to side effects such as runny nose and sore throat, which can last for up to several days. Egg allergy may also be a concern, since flu vaccines are typically made using eggs, however research into egg-allergy and influenza vaccination has led some advisory groups to recommend vaccine delivery protocols for egg allergic persons. On January 17, 2013, the U.S. FDA approved Flublok, a faster-turnaround influenza vaccine which is the first grown in insect cells instead of eggs. It will be available in the 2013–14 season for people age 18–49, and avoids the problem with egg allergies.
Although Guillain-Barré syndrome had been feared as a complication of vaccination, the CDC states that most studies on modern influenza vaccines have seen no link with Guillain-Barré. Getting infected by influenza itself increases both the risk of death and increases the risk of developing Guillain-Barré syndrome to a much higher level than the highest level of suspected vaccine involvement .
Although one review gives an incidence of about one case of Guillain-Barré per million vaccinations, a large study in China, reported in The New England Journal of Medicine covering close to 100 million doses of vaccine against the 2009 H1N1 "swine" flu found only eleven cases of Guillain-Barre syndrome, total incidence in persons vaccinated, actually lower than the normal rate of the disease in China, and no other notable side effects; "The risk-benefit ratio, which is what vaccines and everything in medicine is about, is overwhelmingly in favor of vaccination." Several studies have identified an increased incidence of narcolepsy among recipients of the pandemic H1N1 influenza ASO3-adjuvanted vaccine, efforts to identify a mechanism for this suggest that narcolepsy is autoimmune, and that the H1N1 vaccine may mimic hypocretin, serving as a trigger.
Some injection-based flu vaccines intended for adults in the United States contain thiomersal, a mercury-based preservative. Despite some controversy in the media, the World Health Organization's Global Advisory Committee on Vaccine Safety has concluded that there is no evidence of toxicity from thiomersal in vaccines and no reason on grounds of safety to change to more-expensive single-dose administration.