As of the August 2010 pandemic, H1N1 flu is no longer considered a pandemic. This fact sheet provides historical information about pandemic H1N1 flu and will no longer be updated. Please see the Centers for Disease Control and Prevention website at http://www.cdc.gov/h1n1flu for the latest information about H1N1 flu.
Pandemic H1N1 flu (originally called swine flu) is a respiratory infection. The pandemic H1N1 flu has spread to humans and has reached the level of a pandemic. A pandemic is a worldwide outbreak.
The main risk factor for getting the pandemic H1N1 flu is contact with an infected person. People with the flu can infect others through coughing and sneezing. You can also get the flu by touching an infected object. A chronic health condition such as heart or lung disease, diabetes, or cancer may increase your risk of a more severe form of the flu.
Symptoms may include:
Most people recover at home. Basic care includes rest, fluids, and over-the-counter pain relievers. Antiviral medications may be used. They may be given to prevent or treat an H1N1 infection.
A vaccine is a substance used to protect people from infections caused by bacteria and viruses. There are 2 ways you might receive the H1N1 flu vaccine:
The virus in a vaccine will not make you sick. Be aware that even if you have been vaccinated, you can still get the pandemic H1N1 flu. If you have symptoms, tell your doctor.
Yes, the H1N1 flu vaccine is available. The supply varies by location.
According to the Centers for Disease Control and Prevention (CDC), those who should get vaccinated include:
The Public Health Agency of Canada has similar target groups to the CDC, but also include:
People in these target groups who have had flu-like illness not confirmed to be pandemic H1N1 flu should still be vaccinated.
Pregnant women should be given the flu shot (the inactivated vaccine), not the nasal spray (live, attenuated vaccine).
Should there be a shortage of vaccine, the target populations would consist of:
After the target groups, people aged 25-64 years should get the vaccine. Older adults (over 65 years) will be the last group to receive the vaccine. Older adults have been less likely to become infected with this flu than younger people.
The nasal spray will be given in 2 doses one month apart for children aged 2-9 years. Talk to your child's doctor about what is best for your child. People aged 10-49 years will only need one dose of the nasal spray vaccine.
The shot will be given in 2 doses one month apart to children aged 6 months to 9 years. Some doctors say it is fine to give the doses 3 weeks apart, instead of one month apart. Talk to your child's doctor about what is best for your child. People aged 10 years and older will only need one dose.
Flu season can begin as early as October and last as late as April or May. The best time to get vaccinated is as soon as the vaccine becomes available. Doing so will protect you before the flu comes to your community. The flu season can extend into the spring, so it is important to still get vaccinated if you did not do so early in the season.
Make sure you talk to your healthcare provider about which vaccine is right for you.
At this time, you may not want to get the vaccine if you are allergic to eggs. This is because most vaccines will be made using eggs. Further testing on the H1N1 flu vaccine may indicate that other people need to be cautious as well. Talk to your doctor to learn more.
The nasal spray (live, attenuated vaccine) should not be given to:
Like the seasonal flu vaccine, the H1N1 flu vaccine is not expected to cause problems other than soreness at the injection site. People with specific allergies (eggs, latex, or certain drugs) should check with their doctor before receiving any flu vaccine.
In 1976, a flu vaccine was linked with cases of Guillan-Barre syndrome (GBS), a rare nerve disease causing weakness for several weeks, with some cases being severe enough to require breathing machines. The rate of GBS related to the vaccine was about 1 case per million vaccine doses. Since 1976, flu vaccines have not been clearly linked with GBS.
The CDC has issued some specific guidelines for public facilities. This will help schools, businesses, correctional facilities, and healthcare settings manage an outbreak of the flu. The advised actions may include isolating infected individuals and cleaning the facility. In some cases, the facility may need to be closed for a period of time.
Centers for Disease Control and Prevention
European Commission—Health Information
European Medicines Agency
Public Health Agency of Canada
United Kingdom Department of Health
World Health Organization
Asthma information for patients and parents of patients. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/H1N1flu/asthma.htm. Accessed August 14, 2017.
CDC advisors make recommendations for use of vaccine against novel H1N1, July 29, 2009. Centers for Disease Control website. Available at: https://www.cdc.gov/media/pressrel/2009/r090729b.htm. Accessed August 14, 2017.
Interim recommendations for facemask and respirator use to reduce novel influenza A (H1N1) virus transmission. Centers for Disease Control website. Available at: https://www.cdc.gov/h1n1flu/masks.htm. Accessed August 14, 2017.
Novel H1N1 influenza vaccine. Centers for Disease Control website. Available at: https://www.cdc.gov/h1n1flu/vaccination/public/vaccination_qa_pub.htm. Accessed August 14, 2017.
Novel H1N1 flu (swine flu) and you. Centers for Disease Control website. Available at: https://www.cdc.gov/h1n1flu/qa.htm. Accessed August 14, 2017.
US Food & Drug Administration. Influenza A (H1N1) 2009 monovalent vaccines questions and answers. US Foo &Drug Administration website. Available at https://www.fda.gov/BiologicsBloodVaccines/Vaccines/QuestionsaboutVaccines/ucm182335.htm. Updated June 1, 2017. Accessed August 14, 2017.
Last reviewed September 2018 by David L. Horn, MD, FACP
Last Updated: 8/10/2015