Understanding the Flu Shot
Wednesday, February 27, 2013

Paul Alessi, D.O.

Occasionally, I will have a patient tell me that they received a flu shot, but still ended up getting the flu. While the flu vaccine does not always protect you from getting influenza, it certainly protects you from getting a more serious infection and or dying from influenza. It’s still a great preventive measure to take during flu season, and one I recommend to my patients.

Vaccines mimic the body’s immune response to an infection. When we are exposed to micro-organisms, such as bacteria, viruses, or parasites, our body makes a chemical which activates the immune system.  These chemicals are called antibiotics. A vaccine contains a part of a virus or bacteria which stimulates the immune system without causing an overt infection.

When a vaccine is given, the immune system will remember the exposure to that specific virus or bacteria. Our body’s memory system activates those pre-formed antibodies, which automatically start fighting off the infection. Naturally, this begs the question as to why, if the immune system remembers this exposure, it’s necessary to get a flu vaccine every year while other vaccines can have a lifetime effect.

The flu virus is unique in that it can mutate almost every year and can confuse this memory system, meaning a new vaccine must be developed annually. Some years, the flu virus which circulates in a community can be rather mild and other years it can be much more aggressive. A more aggressive virus can develop into an epidemic, in which large parts of the population become infected.

This was seen during the epidemic of 2009, which resulted in a high number of hospitalizations and deaths nationwide. This year, we have seen an outbreak with a virus not as aggressive, but that has caused widespread infection and a significant number of deaths.

Often, my older patients will question the need for a flu shot if they have never gotten the flu before. I advise them that they may be one of the lucky ones who have never been exposed to anyone who had the flu, or had a very mild infection without significant symptoms. I remind these patients that it’s still advantageous to get the flu vaccine as they can still transmit the virus to others who may be more susceptible.

So far this year, the Centers for Disease Control (CDC) reports that the vaccination rate nationwide is only about 50% -- meaning only half of the at-risk population have been vaccinated.  This vaccination rate is low, especially when we consider that the CDC is reporting 9% mortality.

It is never too late to be vaccinated.  The 2009 epidemic started in late spring and extended over the summer. The vaccine is effective about 2-3 weeks after being injected.  Please consider getting your flu shot, and if you are an older person, adding a pneumonia shot too. Your health is worth it!

Dr. Paul Alessi is a board-certified Internal Medicine Physician with the Kennedy Health Alliance in Cherry Hill. To reach him, call 856-406-4091.