Can the Flu Vaccine Give You the Flu?

Fact or fiction – the flu vaccine can give you the flu?

Early every fall, the CDC recommends that everyone in the United States receive a vaccine against the flu. If you choose to get the flu shot – there are many different options. There are vaccines that protect against either the three or four major strains of the flu. There are special immunizations designed to safeguard the elderly from this nasty disease. There are egg-free varieties and those that can be delivered as a nasal spray. In all cases, the overall goal is to protect the general public from a disease that can result in two weeks of fever and chills and can lead to hospitalization and even death. Yet each year, more and more people choose to opt out of receiving the vaccine. While some of these people merely question the effectiveness of the flu shot, there are others who insist that the vaccine can actually give people the flu.




But can a flu shot- or the alternative nasal spray vaccine- really backfire and give a person the flu?

In a short answer, no, but it’s easy to see where this misconception comes from. Many people know that several versions of the flu vaccine contain an actual virus, and believe that this virus can end up infecting someone after receiving the shot, especially if their immune system is already weak from a recent cold or even just the chill of the season. Yet what few understand is the nature of the virus contained within flu shots. In all flu shots, the virus is inactivated- in a sense, killed. It cannot harm or infect anyone it comes in contact with any more than a dead spider can bite someone. Even before it enters your body, it is harmless, and can serve only to bolster the body’s immune system against a real flu virus.

More recent advances in constructing flu vaccines don’t use a deactivated virus, but instead closely mimic the strain artificially without ever introducing the body to a real virus, dead or otherwise.

As far as nasal sprays go- which are often used on children six months and older- a “cold-adapted” and weakened virus is used instead of a completely inactivated one. While this may seem to pose more of a risk than a shot, the nature of these specially adapted viruses prevents them from surviving in warmer areas of the body, such as the lungs or throat, where the flu takes hold. At worst, a person who uses the nasal spray vaccine may encounter a runny nose and nasal congestion as the body fends off the very mild infection that may have occurred in the coldest places of the nose. This almost always doesn’t last more than a few days, and for most people doesn’t occur at all.

All of this leaves behind a very big question, however: if a flu shot or nasal spray can’t give people the flu, than why do some people still get sick after receiving a vaccine?

flu shot

 There are a number of reasons for this. First off, many people confuse other diseases for the flu during flu season, including the rhinovirus (also known as the common cold) and other repertory viruses. These sicknesses often have flu-like symptoms, but are usually far less severe.

Even when people get the vaccine, however, flu infection can occur. This usually happens when a person has been infected by the virus prior to receiving a vaccine but has yet to have shown symptoms, or when they are infected within the two weeks it takes for the body to adapt itself to the immunization.

Also – the flu vaccine is not always 100% effective. There are many different stands of the flu each season, and while the vaccine usually guards against the most widespread of these strands, even the four and five strand variants cannot guard against every possible type of virus. The annual flu vaccine is prepared months in advance of flu season, and it is possible that the influenza virus may mutate, or evolve, over time, thus rendering the vaccine less effective.

However, what must be understood is that the flu vaccine, in whatever form it might take, is still the best and most effective way of preventing the flu, and every person should receive one during the winter flu season to protect against this nasty and dangerous disease.

And despite what some may say, the flu vaccine cannot actually give you the flu.

 Additional Resources

Devin Windelspecht is a freshman at Northeastern University in Boston MA where he majors in international relations.

Photo credits:

Influenza virus (top and thumbnail): CDC Influenza Laboratory

Individual getting a flu shot:,_left,_the_command_master_chief_of_the_aircraft_carrier_USS_Abraham_Lincoln_(CVN_72),_receives_his_annual_flu_shot_Sept_130919-N-MK401-017.jpg

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