Getting your flu shot is important, even if it’s not 100% effective
Seasonal Influenza is a major global health concern. Worldwide, these annual epidemics are estimated to result in about 3 to 5 million cases of severe illness, and about 250,000 to 500,000 deaths. In industrialized countries most deaths associated with influenza occur among people age 65 or older.
In the United States, the overall burden of influenza disease during 2014-2015 across all age groups was 40 million flu illnesses, 19 million flu-associated medical visits and 970,000 flu-associated hospitalizations resulting in more than 36,000 deaths due to influenza-related complications. The influenza vaccine is one of the best preventive measures available. For the 2014–15 influenza season, CDC used updated estimates of influenza vaccination coverage, vaccine effectiveness, and influenza hospitalizations rates. Based on these methods, CDC estimates that influenza vaccination prevented approximately 67,000 influenza-associated hospitalizations, or 6.5% of potential influenza-associated hospitalizations. In addition, influenza vaccination prevented an estimated 1.9 million illnesses and 966,000 medical visits associated with influenza.
How is the Influenza Vaccine Made?
The World Health Organization (WHO) works with five labs around the world, which are located in the United States, China, Japan, Australia and the United Kingdom. These labs collect specimens from hundreds of countries around the world, which do surveillance as to what type of influenza is affecting their populations. Since flu strains move fairly predictably around the world, the decision is then made months in advance as to which strains should be included in the vaccine for the following year. Between 1988 and 2008, the vaccine was determined to be a good match in 16 of those 20 years.
There are three main types of Influenza virus which cause disease in humans; A, B, and C. Influenza A and B are those that are associated with more severe illness and are included by the WHO in the annual flu vaccine each year. When there are three strains in the flu vaccine (trivalent), there are two A’s and one B. With the quadrivalent vaccine, two strains each of A and B are included. For influenza A, there are two major antigens, or proteins on the influenza virus, H (hemagglutinin) and N (neuramidase), both of which have multiple subtypes, including 18 H and 11 N antigens. These antigens combine as different strains of influenza, such as H1N1 and H3N2. A quadrivalent vaccine with 2 A’s could have, for example, both the H1N1 and H3N2 and two Influenza B viruses, which are named by the lineages and strains.
The information from the centers worldwide is evaluated to determine the composition of the next batch of vaccine. Vaccine manufacturers then utilize hundreds of millions of laboratory grade fertilized hen’s eggs where the vaccine viruses are injected and incubated for several days to allow viruses to replicate. The virus-containing fluid is harvested from the eggs. For injectable flu vaccine, the influenza viruses for the vaccine are inactivated (killed) and virus antigen is purified. For this reason, you cannot get the flu from the flu vaccine.
There is extensive testing for safety prior to the distribution of the approximately 250 million doses to U.S. providers’ offices and clinics. This process is truly a testament to the ability of science to help all of mankind and should be both greatly appreciated and utilized.
How Does the Influenza Vaccine Work?
The seasonal flu vaccine protects against the influenza viruses that research indicates will be the most common during the upcoming season. From your body’s perspective, getting the flu vaccine looks like an oncoming case of the flu, though it is not actually the flu. Made of inactivated or weaker viruses, the vaccine causes the body to make antibodies toward those strains of the influenza virus. These antibodies develop in the body about two weeks after vaccination and provide protection against infection with the strains that are in the vaccine. They may also be of benefit for closely related strains.
How Effective is the Flu Vaccine?
The Centers for Disease Control (CDC) conducts studies to measure the benefits of seasonal flu vaccination each flu season to help determine how well flu vaccines are working. The effectiveness of the vaccine is measured by comparing those who get the vaccine vs. those who were given a placebo. These vaccine effectiveness (VE) studies regularly assess and confirm the value of flu vaccination as a public health intervention. While vaccine effectiveness can vary, recent studies show vaccine reduces the risk of flu illness by about 50% to 60% among the overall population during seasons when most circulating flu viruses are like the vaccine viruses.
This effectiveness is a major benefit because of the widespread cases or prevalence of the flu, which affects 5-10% of adults and 20-30% of children each year. There are approximately 50 million cases of influenza that occur in the United States each year. Of these, the very young and old are most seriously affected, with adults 65 years of age and older at the highest risk of influenza complications. They are 10-30 times more likely to be hospitalized due to influenza-related complications. The effectiveness of the vaccine is measured by comparing those who get the vaccine vs. those who were given a placebo.
Flu Vaccine - Prevention, Protection and Herd Immunity:
The influenza vaccine has been shown over many years to be one of the most important preventive measures against the flu. Other actions include hand washing, coughing and sneezing into one’s own sleeve, avoiding others who are ill and staying home when you are sick.
It is important for most of the population to receive the flu vaccine annually. It is estimated that 70 percent of the population needs to receive the flu vaccine to ensure “herd immunity” which protects members of the population who cannot or did not receive the influenza vaccine.
This year, the CDC advises against using the intranasal live attenuated (weakened) vaccine due to concerns of its effectiveness. Everyone who can receive the influenza vaccine should receive it by injection as soon as possible this season. And remember, even if it’s not a perfect match, it can protect you and your loved ones from getting a potentially life-threatening, yet preventable, disease.