Flu shot cannot give you influenza, doctors say

Doctors explain that flu vaccines do not cause influenza and that common mild side effects reflect the immune response and usually resolve within a day or two.

Many people worry that getting a flu shot can cause influenza, a belief that surveys have shown in roughly a portion of the public. Health experts interviewed for the article say that most flu vaccines do not contain a live virus and cannot cause the illness. The nasal spray vaccine is a live-attenuated form, which contains a weakened virus. The article also notes that mild side effects are common after vaccination and can resemble flu symptoms but are typically shorter and less severe. Key points: - The article reports that most flu vaccines use inactivated virus or pieces of the virus, and cannot cause influenza. - The nasal spray vaccine is identified as a live-attenuated influenza vaccine that contains a weakened form of the virus. - Common side effects listed include injection-site soreness, redness or swelling, headache, low-grade fever, nausea, and muscle aches; these usually begin soon after vaccination and last one to two days. - It is noted that some people, including pregnant women and recipients of high-dose vaccines, may be more likely to report side effects. - The article states it takes about two weeks after vaccination for full immunity to develop, so people can still catch the flu shortly after getting the shot. Summary: The reporting clarifies that flu shots are not a source of influenza and that brief, mild side effects often reflect the body building protection. The article notes that testing can be used when symptoms make the cause unclear and that the timeline for developing full immunity is about two weeks. Undetermined at this time.