Influenza vaccine

An influenza vaccine helps protect people from the flu. This illness is caused by influenza viruses. These viruses change very quickly through a process called antigenic drift. This means a tiny mutation happens, and a new strain arises. Because the virus changes so fast, scientists must develop new versions twice a year.

Most vaccines provide modest to high protection against the virus. They can even reduce how sick you feel if you catch a strain not in the vaccine. It takes about two weeks for your body to form protective antibodies after you get the shot.

There are a few different ways a vaccine works. Some vaccines use inactive viruses, which means the virus is not alive. Other vaccines use weakened viral forms.

You can receive these in different ways. Some are injected into a muscle, which is called an intramuscular injection. Others are sprayed into the nose, known as an intranasal spray. Some can even be injected into the middle layer of the skin, called an intradermal injection.

People have been working on these vaccines for a long time. During the Spanish flu pandemic in 1918, doctors tried many things to help patients. In 1931, Ernest William Goodpasture and his colleagues at Vanderbilt University found a way to grow viruses in hen's eggs. Other workers like Thomas Francis, Jonas Salk, Wilson Smith, and Macfarlane Burnet used this to make the first experimental vaccines. By the 1940s, the US military developed the first approved inactivated vaccines for use during World War II.

Science has continued to improve how we make these medicines. In 2012, the US Food and Drug Administration approved vaccines grown in cell cultures. In 2013, they approved vaccines made from recombinant proteins. Many vaccines are now quadrivalent, meaning they target four different lineages of the virus.

For example, the FDA approved Fluzone High-Dose Quadrivalent in November 2019. In 2024, the FDA even recommended removing one specific lineage called B/Yamagata from vaccines. This is because that strain might have become extinct during the COVID-19 pandemic.

Getting a flu shot is a way to stay healthy and help others. The CDC recommends yearly vaccination for almost everyone over six months old. This is especially important for high-risk groups like pregnant women, the elderly, and young children.

Even though side effects like a sore arm or a fever can happen, the vaccine is generally safe. One study even found that a flu shot was as effective or better at preventing heart attacks than quitting smoking. By getting vaccinated, you help stop the spread of the virus to your community.