Influenza Vaccine: Everything You Need to Know
Lauren Foster

Influenza Vaccine: Everything You Need to Know

The Centers for Disease Control and Prevention define the flu as a contagious respiratory illness caused by influenza viruses that infect the nose, throat and lungs. The flu virus is highly contagious, spreading mainly through cough and sneeze particles from one person to another. It can also be transferred by touching infected surfaces or objects and then by touching your own mouth, eyes or nose. The virus can spread to others one day prior to the onset of symptoms and those infected remain contagious for up 7 days after becoming sick.

We’re all familiar with the common symptoms of the flu, but what we may not know is that there are a number of complications that can result from the flu and certain people are at greater risk, including the elderly, young children, pregnant women and people with certain health conditions. Some of the complications include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.

The flu affects different people in different ways but the best way for everyone to prevent infection is by getting a flu vaccine each year. Not only does this reduce the chances of getting sick with the flu, it lessens the chances of spreading it to others. We’re all prone to infection, but rates are highest among children so everyone six months and older should always get a flu vaccine. In the United States, flu season can start as early as October and last through May, so get vaccinated as soon as the vaccine becomes available in your community.

The Flu and its Shot
Every flu season is unique because flu viruses are constantly changing; this effect is known as antigenic drift. Viruses will change from one season to the next and can even change during the course of one season. The flu shot is made up of inactivated vaccines, or killed viruses, and is formulated each year to keep up with the antigenic drift. This is why it’s important to get vaccinated every year. There are three kinds of influenza viruses that most commonly circulate among us today. These include influenza B viruses, influenza A (H1N1) viruses, and influenza A (H3N2) viruses. Extensive research indicates which viruses will be most common during the upcoming season and one virus from each of the three groups is used to produce the seasonal influenza vaccine. This three-component vaccine is called a trivalent. Once vaccinated, it takes about two weeks for the antibodies to develop in the body and protect against influenza.

The effectiveness of the flu vaccine in protecting and preventing the spread of the virus is inconsistent, but the main factors that determine how well the vaccine will work include characteristics of the person being vaccinated such as age and health status, and the similarity or “match” between the virus strains in the vaccine and those circulating in the community. There is always the possibility of a less-than-optimal match, but antibodies made in response to vaccination with one flu virus can sometimes provide protection against different but related viruses. Unfortunately, some people may remain unprotected despite being vaccinated. This is more likely to occur among people with weakened immune systems or the elderly, but even among these people, a flu vaccine can still help prevent complications and lessen illness severity.

This Season’s Forecast
There are several different manufacturers that produce trivalent influenza vaccines for the US market and they have projected that between 146 million and 149 million doses of flu vaccine will be produced this year. The vaccine is made from the following three viruses:

  1. A/California/7/2009 (H1N1)pdmo9-like virus
  2. A/Victoria/361/2011 (H3N2)-like virus
  3. B/Wisconsin/1/2010-like virus (from the B/Yamagata lineage of viruses)

Get Vaccinated
Receiving the influenza vaccine each year is by far the best way to protect yourself and those around you against the seasonal flu. Antiviral drugs, prescribed by a doctor, can act as a second line of defense against the flu, but it’s recommended that everyone over the age of six months gets vaccinated. And of course healthy habits, regular hand washing, and covering your mouth when you cough are all important additional ways to help prevent the spread of the flu. Keep in mind that the flu vaccine contains three viruses, so even when the match is weak or less effective against one virus, the vaccine may still protect against the others.


  1. CDC – Seasonal Influenza (Flu):