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What You Should Know for the 2014-2015 Influenza Season

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Note: On February 26, 2015, the Advisory Committee on Immunization Practices (ACIP) voted on its annual influenza vaccine recommendations. For 2015-2016, ACIP recommends annual influenza vaccination for everyone 6 months and older with either LAIV or IIV, with no preference expressed for either vaccine when either one is otherwise appropriate. More information on this vote is available at the CDC Newsroom. The LAIV content on this web page will be updated after the 2015-2016 recommendations are approved by the CDC Director and published in the MMWR.

What sort of flu season are we having?

As of February 28, 2015, flu activity is still elevated but continues to decrease in the United States. Mismatched H3N2 flu viruses continue to predominate; however, more recently, an increase in influenza B viruses has been detected in parts of the country. The predominance of H3N2 viruses this season has caused a significant burden of serious disease in older people. The flu-associated hospitalization rate among people 65 and older is the highest rate recorded since CDC began tracking that data in 2005. As of February 28, the hospitalization rate in this age group this season is 266.1 per 100,000 population. The previous highest hospitalization rate recorded was 183.2 per 100,000 population during the 2012-13 flu season (also among people 65 and older). (2012-2013 was the last H3N2 predominant season.) Overall, nearly 60 percent of flu-associated hospitalizations have been among people 65 years and older this season.

Children 0-4 years of age have the second-highest hospitalization rate this season. Like older people, children often fare worse during H3N2-predominant seasons; however, the hospitalization rate for the 0-4 age group this season so far is less than what was seen for the same week during the 2012-2013 season (47.8 per 100,000 this season compared to 54.6 per 100,000 population during 2012-2013).

Is there any unusual disease activity going on this season?

Since December 2014, multiple states have notified CDC of laboratory-confirmed influenza infections in persons who have swelling of their salivary glands (a condition called ‘parotitis’). Of the cases of influenza infection with parotitis that have been reported to CDC, the majority have occurred in children with influenza A (H3) infection, and have resulted in mild illness. No deaths have been reported. CDC is currently investigating the situation in order to understand the characteristics of patients and the occurrence of parotitis.

Parotitis is not a common symptom of influenza infection, although cases of parotitis with influenza infection have been reported in the past. Parotitis is much more commonly seen following infection with other pathogens such as the mumps virus. Symptoms of influenza infection include fever, chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headache, fatigue (tiredness), and sometimes vomiting and diarrhea (more common in children than adults).

Is the U.S. having a flu epidemic?

The United States experiences epidemics of seasonal flu each year. This time of year is called "flu season." While influenza activity has declined in recent weeks and the flu season is coming to a close, most of CDC’s influenza surveillance systems still show elevated activity. As long as flu viruses are circulating, clinicians and the public should be aware that there are treatment drugs for influenza and that people who are very sick or people with high risk factors who get flu symptoms should be evaluated for possible treatment.

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How many people have died from flu this year?

CDC does not count how many people die from flu each year. Unlike flu deaths in children, flu deaths in adults are not nationally reportable. However, CDC has two flu surveillance systems that are used to monitor relative levels of flu-associated deaths. One is the “122 Cities Mortality Reporting System” and the other is mortality data collected by the National Center for Health Statistics. Both of these systems track the proportion of death certificates processed that list pneumonia or influenza (P&I) as the underlying or contributing cause of death of the total deaths reported. These systems provide an overall indication of whether flu-associated deaths are elevated, but do not provide an exact number of how many people died from flu. For more information, see Overview of Influenza Surveillance in the United States, “Mortality Surveillance.”

CDC also uses modeling studies to estimate numbers of flu-related deaths, but these studies apply only to past seasons and are not done each year. For more information, see Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu.

Why is it difficult to know how many people die from flu?

There are several factors that make it difficult to determine accurate numbers of deaths caused by flu regardless of reporting. Some of the challenges in counting influenza-associated deaths include the following: the sheer volume of deaths to be counted; not everyone that dies with an influenza-like illness is tested for influenza; and influenza-associated deaths are often a result of complications secondary to underlying medical problems, and this may be difficult to sort out. For more information, see Estimating Seasonal Influenza-Associated Deaths in the United States: CDC Study Confirms Variability of Flu.

Will new flu viruses circulate this season?

Flu viruses are constantly changing and it's not unusual for new seasonal flu viruses to appear each year. These are viruses that have small antigenic or genetic changes but which have evolved from previously circulating human seasonal flu viruses. When viruses change in that way, they are said to be “drifted” viruses. Most of the influenza A (H3N2) viruses circulating so far this season are different (drifted) from the H3N2 vaccine virus component.

(Once in a while, a new, non-human flu virus emerges to infect people. This is very different from the drift that is observed with seasonal flu viruses, and can cause a pandemic.) For more information about how flu viruses change, visit How the Flu Virus Can Change.

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When did flu activity begin and when did it peak?

The timing of flu is very unpredictable and can vary in different parts of the country and from season to season. However, seasonal flu activity can begin as early as October and continue to occur as late as May. Flu activity most commonly peaks in the U.S. between December and February. On March 6, 2015, CDC published a Morbidity and Mortality Weekly Report (MMWR) that summarized flu activity this season from September 28, 2014 through February 21, 2015. This report showed that flu activity in the United States began to increase in mid-November, remained elevated through February 21, and was expected to continue for several more weeks. This season, several surveillance markers, such as respiratory specimens positive for flu, outpatient illness for influenza-like illness (ILI), and geographic spread of influenza peaked between late December and early January (week 52-week1).

What should I do to protect myself from flu?

CDC recommends a yearly flu vaccine for everyone 6 months of age and older as the first and most important step in protecting against this serious disease. People should begin getting vaccinated soon after flu vaccine becomes available, ideally by October, to ensure that as many people as possible are protected before flu season begins. However, as long as flu viruses are circulating in the community, it’s not too late to get vaccinated.

In addition to getting a seasonal flu vaccine if you have not already gotten vaccinated, you can take everyday preventive actions like staying away from sick people and washing your hands to reduce the spread of germs. If you are sick with flu, stay home from work or school to prevent spreading flu to others.

Also, it’s important to remember that antiviral drugs can be used to treat flu illness and prevent serious flu complications. Antiviral drugs become even more important when circulating flu viruses are different from the vaccine viruses, which can mean that the vaccine doesn't work as well in protecting against infection with those viruses. People at high risk (such as children younger than 2 years, adults 65 and older, pregnant women, people who have medical conditions) or are very sick (such as those hospitalized because of flu) should get antiviral drugs. Some other people can be treated with antivirals, at their health care professional’s discretion. Treating high risk people or people who are very sick with flu with antiviral drugs is very important. It can mean the mean the difference between having a milder illness instead of very serious illness that could result in a hospital stay.

Antiviral drugs are prescription drugs that can be used to treat the flu or to prevent infection with flu viruses. Treatment with antivirals works best when begun within 48 hours of getting sick, but can still be beneficial when given later in the course of illness. Treatment with flu antiviral drugs can make your illness milder and shorter. Treatment with antivirals also can lessen serious flu complications that can result in hospitalization or death. Antiviral drugs are effective across all age-and risk groups. Studies show that antiviral drugs are under-prescribed for people who are at high risk of complications who get flu. Originally this season, two FDA-approved influenza antiviral agents were recommended for use in the United States during the 2014-2015 influenza season: oseltamivir and zanamivir. However, on December 19, 2014, the FDA also approved peramivir (trade name Rapivab®) to treat influenza infection in adults age 18 and older.

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What should I do to protect my loved ones from flu?

Encourage your loved ones to get vaccinated. Vaccination is especially important for people at high risk for serious flu complications, and their close contacts. Also, if you have a loved one who is at high risk of flu complications and they develop flu symptoms, encourage them to get a medical evaluation for possible treatment with influenza antiviral drugs. CDC recommends that people who are at high risk for serious flu complications who get the flu this season be treated with influenza antiviral drugs as quickly as possible. People who are not at high risk for serious flu complications who get the flu may also be treated with influenza antiviral drugs, especially if treatment can begin within 48 hours.

Children between 6 months and 8 years of age may need two doses of flu vaccine to be fully protected from flu. The two doses should be given at least 4 weeks apart. Your child’s doctor or other health care professional can tell you whether your child needs two doses. For children who have had one dose already but need two to be fully protected against flu, now may be a good time to get the second dose. Visit Children, the Flu, and the Flu Vaccine for more information.

Children younger than 6 months are at higher risk of serious flu complications, but are too young to get a flu vaccine. Because of this, safeguarding them from flu is especially important. If you live with or care for an infant younger than 6 months of age, you should get a flu vaccine to help protect them from flu. See Advice for Caregivers of Young Children for more information.

In addition to getting vaccinated, you and your loved ones can take everyday preventive actions like staying away from sick people and washing your hands to reduce the spread of germs. If you are sick with flu, stay home from work or school to prevent spreading influenza to others.

What kind of vaccines are available in the United States for 2014-2015?

A number of different manufacturers produce trivalent (three component) influenza vaccines for the U.S. market, including intramuscular (IM), intradermal, and nasal spray vaccines. Some seasonal flu vaccines are formulated to protect against four flu viruses (quadrivalent flu vaccines). See Key Facts About Seasonal Flu Vaccine and How Flu Vaccines Are Made for more information.

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Are there new recommendations for the 2014-2015 influenza season?

Recommendations on the control and prevention of influenza are published annually, in late summer or early fall. Recommendations for the 2014-2015 season are available in the Morbidity and Mortality Weekly Report (MMWR). During the 2014-2015 flu season, CDC recommended use of the nasal spray vaccine (LAIV) for healthy* children 2 through 8 years of age, when it was immediately available and if the child had no contraindications or precautions to that vaccine. For more information, see Nasal Spray Flu Vaccine in Children 2 through 8 Years Old or the 2014-2015 MMWR Influenza Vaccine Recommendations. However, on February 26, 2015, the Advisory Committee on Immunization Practices (ACIP) did not renew the preferential recommendation for LAIV for the 2015-2016 season. The ACIP recommendations must be approved by the CDC Director at which point they are published in the MMWR and become CDC policy. More information on this vote is available at the CDC Newsroom.

(*“Healthy” in this instance refers to children 2 years through 8 years old who do not have an underlying medical condition that predisposes them to influenza complications.)

Visit What’s New on this Site to sign up and receive updates from the CDC Influenza site.

How much flu vaccine is available this season?

Currently, seven influenza vaccine manufacturers are projecting that as many as 151 million to 156 million doses of influenza vaccine will be available for use in the United States during the 2014-2015 influenza season.

Of the 151 million to 156 million doses of influenza vaccine projected to be available for the 2014-2015 season, manufacturers estimate that 76 million doses will be quadrivalent flu vaccine.

Where can I get a flu vaccine?

Flu vaccines are offered by many doctor’s offices, clinics, health departments, pharmacies and college health centers, as well as by many employers, and even by some schools.

Even if you don’t have a regular doctor or nurse, you can get a flu vaccine somewhere else, like a health department, pharmacy, urgent care clinic, and often your school, college health center, or work.

Visit the HealthMap Vaccine Finder to locate where you can get a flu vaccine.

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What flu viruses does this season’s vaccine protect against?

Flu vaccines are designed to protect against the main flu viruses that research suggests will be the most common during the upcoming season. Three kinds of flu viruses commonly circulate among people today: influenza A (H1N1) viruses, influenza A (H3N2) viruses, and influenza B viruses.

All of the 2014-2015 influenza vaccine is made to protect against the following three viruses:

  • an A/California/7/2009 (H1N1)pdm09-like virus
  • an A/Texas/50/2012 (H3N2)-like virus
  • a B/Massachusetts/2/2012-like virus.

Some of the 2014-2015 flu vaccine is quadrivalent vaccine and also protects against an additional B virus (B/Brisbane/60/2008-like virus).

Vaccines that give protection against three viruses are called trivalent vaccines. Vaccines that give protection against four viruses are called quadrivalent vaccines.

More information about influenza vaccines is available at Preventing Seasonal Flu With Vaccination.

What is flu vaccination using a jet injector?

On August 14, 2014, the U.S. Food and Drug Administration (FDA) approved use of one jet injector device (the PharmaJet Stratis 0.5ml Needle-free Jet Injector) for delivery of one particular flu vaccine (AFLURIA® by bioCSL Inc.) in people 18 through 64 years of age. A jet injector is a medical device used for vaccination that uses a high-pressure, narrow stream of fluid to penetrate the skin instead of a hypodermic needle. For more information, see Flu Vaccination by Jet Injector.

How effective is the flu vaccine?

Influenza vaccine effectiveness (VE) can vary from year to year and among different age and risk groups. For more information about vaccine effectiveness, visit How Well Does the Seasonal Flu Vaccine Work? Most of the circulating H3N2 flu viruses this season are different from the vaccine virus. This is probably responsible for reduced vaccine effectiveness against those viruses this season. The latest vaccine effectiveness estimates for the 2014-15 season were presented to the Advisory Committee for Immunization Practices (ACIP) on February 26, 2015, and are summarized in a CDC spotlight article.

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How long does a flu vaccine protect me from getting the flu?

Multiple studies conducted over different seasons and across vaccine types and influenza virus subtypes have shown that the body’s immunity to influenza viruses (acquired either through natural infection or vaccination) declines over time. The decline in antibodies is influenced by several factors, including the antigen used in the vaccine, the age of the person being vaccinated, and the person's general health (for example, certain chronic health conditions may have an impact on immunity). When most healthy people with regular immune systems are vaccinated, their bodies produce antibodies and they are protected throughout the flu season, even as antibody levels decline over time. Older people and others with weakened immune systems may not generate the same amount of antibodies after vaccination; further, their antibody levels may drop more quickly when compared to young, healthy people.

For everyone, getting vaccinated each year provides the best protection against influenza throughout flu season. It’s important to get a flu vaccine every season, even if you got vaccinated the season before and the viruses in the vaccine have not changed for the current season.

Is this season's vaccine a good match for circulating viruses?

Laboratory analysis of circulating flu viruses this season indicates that most of the H3N2 viruses are antigenically or genetically different than the H3N2 vaccine virus. This is probably why vaccine effectiveness estimates this season show that the vaccine is not working as well as usual against H3N2 viruses. However, the vaccine should work well against about one-third of circulating H3N2 viruses and against H1N1 and influenza B viruses.

Why doesn’t this season’s vaccine contain the right H3N2 virus?

Experts must pick which viruses to include in the vaccine many months in advance in order for vaccine to be produced and delivered on time. And flu viruses change constantly (called drift); they can change from one season to the next or they can even change within the course of one flu season. Because of these factors, there is always the possibility of a less than optimal match between circulating viruses and the viruses in the vaccine.

When the vaccine viruses for 2014-2015 were selected, A/Texas/50/2012 was the most common circulating influenza H3N2 virus, so it was chosen to be included in the vaccine. The drifted H3N2 viruses that are circulating this season were first detected during routine surveillance testing during late March 2014, after World Health Organization (WHO) recommendations for the vaccine composition for the Northern Hemisphere for the 2014-2015 season had been made (in mid-February). At that time, just a very small number of these viruses had been found among the thousands of specimens that had been collected and tested and there was no way to predict that they would circulate widely.

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Can the vaccine provide protection even if the vaccine is not a "good" match?

Yes, antibodies made in response to vaccination with one flu virus can sometimes provide protection against different but related viruses. A less than ideal match may result in reduced vaccine effectiveness against the virus that is different from what is in the vaccine, but it can still provide some protection against influenza illness.

In addition, it's important to remember that the flu vaccine contains three or four flu viruses (depending on the type of vaccine you receive) so that even when there is a less than ideal match or lower effectiveness against one virus, the vaccine may protect against the other viruses.

For these reasons, even during seasons when there is a less than ideal match, CDC continues to recommend flu vaccination for everyone 6 months and older. Vaccination is particularly important for people at high risk for serious flu complications, and their close contacts.

Can I get vaccinated and still get the flu?

Yes. It’s possible to get sick with the flu even if you have been vaccinated (although you won’t know for sure unless you get a flu test). This is possible for the following reasons:

  • You may be exposed to a flu virus shortly before getting vaccinated or during the period that it takes the body to gain protection after getting vaccinated. This exposure may result in you becoming ill with flu before the vaccine begins to protect you. (About 2 weeks after vaccination, antibodies that provide protection develop in the body.)
  • You may be exposed to a flu virus that is not included in the seasonal flu vaccine. There are many different flu viruses that circulate every year. The flu vaccine is made to protect against the three or four flu viruses that research suggests will be most common.
  • Unfortunately, some people can become infected with a flu virus the flu vaccine is designed to protect against, despite getting vaccinated. Protection provided by flu vaccination can vary widely, based in part on health and age factors of the person getting vaccinated. In general, the flu vaccine works best among healthy younger adults and older children. Some older people and people with certain chronic illnesses may develop less immunity after vaccination. Flu vaccination is not a perfect tool, but it is the best way to protect against flu infection.

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What is CDC doing to monitor vaccine effectiveness for the 2014-2015 season?

CDC collaborates with other partners each season to assess how well the seasonal vaccines are working. During the 2014-2015 season, CDC is planning multiple studies on the effectiveness of both the flu shot and the nasal-spray flu vaccine. These studies measure vaccine effectiveness in preventing laboratory-confirmed influenza among persons 6 months of age and older. A summary of CDC’s latest vaccine effectiveness estimates for the 2014-15 season is available in a CDC spotlight article.

Where can I find information about vaccine supply?

Information about flu vaccine supply is available here: Seasonal Influenza Vaccine & Total Doses Distributed

Is there treatment for the flu?

Yes. If you get sick, there are drugs that can treat flu illness. They are called antiviral drugs and they can make your illness milder and make you feel better faster. They also can prevent serious flu-related complications, like pneumonia. For more information about antiviral drugs, visit Treatment (Antiviral Drugs).

Is there an antiviral drug shortage?

Manufacturers have stated they have sufficient product on hand to meet the projected high demand for the 2014-2015 flu season.

However, depending on local supply and demand, spot shortages of influenza antiviral drugs can occur. Patients should consider calling a pharmacy in advance to see if they have drug on their shelf. If the pharmacy does not have product, they may be able to identify another pharmacy in the area that has antiviral drugs in stock.

During 2014-2015, for long-term care facilities experiencing difficulty accessing antiviral supplies, CDC was prepared to coordinate with commercial partners to facilitate the rapid resolution of large orders of antiviral drugs for institutional outbreaks. Beginning on Monday, Jan. 12, the Division of Strategic National Stockpile (DSNS) is available from 7:00 a.m. to 7:00 p.m., EST Monday through Friday, to assist public health officials and health care facilities by coordinating with supply chain partners to rapidly redirect supply to the identified location. Contact DSNS at dsns-Request@cdc.gov for assistance with facility specific unmet antiviral drug supply needs. For emergency needs overnight and on weekends, public health officials can contact the CDC Emergency Operations Center through established protocols.

CDC and FDA will continue to work with manufacturers to assess influenza antiviral supply this season.

What is antiviral resistance?

Antiviral resistance means that a flu virus has changed in such a way that antiviral drugs are less effective. Samples of flu viruses collected from around the United States and worldwide are studied at CDC to determine if they are becoming resistant to any of the FDA-approved influenza antiviral drugs.

What is CDC doing to monitor antiviral resistance in the United States during the 2014-2015 season?

CDC is continuing to collect and monitor flu viruses for changes through an established network of domestic and global surveillance systems. Additionally, CDC is working with the state public health departments and the World Health Organization to collect additional information on antiviral resistance in the United States and worldwide. The information collected will assist in making informed recommendations regarding use of antiviral drugs to treat influenza.

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I am a U.S. resident experiencing some flu-like symptoms (e.g. fever, headache, muscle aches). How do I know if I have seasonal influenza or Ebola?

Influenza is a respiratory disease that is spread primarily from person to person through coughs and sneezes. Ebola virus is not a respiratory disease and is only spread through direct contact with blood or body fluids of a person who is sick with Ebola.

Seasonal influenza and Ebola virus infection can cause some similar symptoms. However, of these viruses, your symptoms are most likely caused by seasonal influenza. Influenza is very common. Millions of people are infected, hundreds of thousands are hospitalized and thousands die from flu each year. In the United States, fall and winter is the time for flu. While the exact timing and duration of flu seasons vary, outbreaks often begin in October and can last as late as May. Most of the time flu activity peaks between December and February. Information about current levels of U.S. flu activity is available in CDC’s weekly FluView report.

In the United States, infections with Ebola virus have been exceedingly uncommon. There is widespread transmission of Ebola virus disease in West Africa.

It is usually not possible to determine whether a patient has seasonal influenza or Ebola infection based on symptoms alone. However, there are tests to detect seasonal influenza and Ebola infection. Your doctor will determine if you should be tested for these illnesses based on your symptoms, clinical presentation and recent travel or exposure history. (For information regarding the signs and symptoms of Ebola, and whether you may need to be tested, please review the Ebola case definitions.)

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I am a U.S. resident experiencing flu-like symptoms (e.g. coughing, fever, sore throat, etc.). How do I know if I have seasonal influenza or MERS (Middle Eastern Respiratory Syndrome)?

Seasonal influenza and MERS can cause similar respiratory symptoms. However, of these viruses, your symptoms are most likely caused by seasonal influenza. In the United States, fall and winter is the time for flu. While the exact timing and duration of flu seasons vary, flu outbreaks often begin in October and can last as late as May. Most of the time flu activity peaks between December and February. Information about current levels of flu activity is available in CDC’s weekly FluView report.

MERS is not common in the United States. However, in 2014, two people who recently traveled from Saudi Arabia to the United States had MERS. All MERS cases have been linked to countries in or near the Arabian Peninsula.

It is not possible to determine whether a patient has seasonal influenza, or MERS, or an illness due to another pathogen based on symptoms alone. However, there are tests to detect seasonal influenza and MERS. Your doctor will determine if you should be tested for any of these illnesses based on your symptoms, clinical presentation and recent travel history. (For information regarding the signs and symptoms of MERS, and whether you may need to be tested, please review the MERS case definitions.)

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