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Medical Author:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• Flu vaccine (flu shot) facts
• What is flu?
• Why vaccinate for the flu?
• What are the different types of flu vaccines?
• What flu viruses does the flu vaccine protect against?
• How does the flu vaccine work to prevent the flu?
• When should one receive the flu vaccine?
• Who should receive the flu vaccine?
• Who should not receive the flu vaccine?
• What are risks and side effects of the flu vaccine?
• Can the flu vaccine give me the flu?
• What should I do about adverse reactions to the flu vaccine?
• How effective is the flu shot?
• What was the novel H1N1 (swine flu) vaccine?
• What is the best way to locate a flu shot clinic?
• Patient Comments: Flu Vaccination - Side Effects
• Flu Vaccination Index

Can the flu vaccine give me the flu?

The LAIV (nasal-spray flu vaccine) can cause mild respiratory side effects in some people, including runny nose, headache, sore throat, and cough. Children who receive the vaccine may also develop mild fever and muscle aches. These side effects are not the flu and generally not as severe as the flu. However, because the vaccine contains weakened live virus, it is recommended that people at high risk for serious complications of the flu receive the inactivated rather than the nasal-spray vaccine.

What should I do about adverse reactions to the flu vaccine?

You should contact your health care professional in the case of any serious side effects. Mild side effects such as soreness at the injection site typically resolve on their own without treatment.

How effective is the flu shot?

The effectiveness of the flu vaccine is dependent upon the extent of the match between the virus strains used to prepare the vaccine and those viruses in actual circulation. The age and health status of the individual also play a role in determining the effectiveness of the vaccine. Research has shown that when there is a good match between the virus strains chosen for the vaccine and those in circulation, the vaccine prevents influenza illness in approximately 70%-90% of healthy adults under 65 years of age.

A study of children from 1-15 years of age showed that inactivated influenza vaccine was 77%-91% effective in preventing influenza respiratory illness. The effectiveness of the vaccine in preventing respiratory illness in people over 65 years of age is somewhat lower. Among older people who reside in nursing homes, influenza vaccine is most effective in preventing severe illness, secondary complications, and deaths. The vaccine can be 50%-60% effective in preventing influenza-related hospitalization or pneumonia and 80% effective in preventing influenza-related death, although the effectiveness in preventing influenza respiratory illness can be as low as from 30%-40%.