What sort of flu season is expected this year?
It’s not possible to predict what this flu season will be like. Flu seasons are unpredictable in a number of ways. While flu spreads every year, the timing, severity, and length of the season usually varies from one season to another.
Flu viruses are constantly changing so it’s not unusual for new flu viruses to appear each year. For more information about how flu viruses change, visit How the Flu Virus Can Change.
The timing of flu is very unpredictable and can vary from season to season. Flu activity most commonly peaks in the U.S. between December and February. However, seasonal flu activity can begin as early as October and continue to occur as late as May.
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. While there are many different flu viruses, the seasonal flu vaccine is designed to protect against the main flu viruses that research suggests will cause the most illness during the upcoming flu season. 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.
In addition to getting 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.
Encourage your loved ones to get vaccinated as soon as vaccine becomes available in their communities, preferably by October. Vaccination is especially important for people at high risk for serious flu complications, and their close contacts.
Children between 6 months and 8 years of age may need two doses of flu vaccine to be fully protected from flu. Your child’s doctor or other health care professional can tell you whether your child needs two doses. 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.
CDC recommends that people get vaccinated against flu soon after vaccine becomes available, preferably by October.
It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against the flu.
Doctors and nurses are encouraged to begin vaccinating their patients soon after vaccine becomes available, preferably by October so as not to miss out on opportunities to vaccinate. Those children 6 months through 8 years of age who need two doses of vaccine should receive the first dose as soon as possible to allow time to get the second dose before the start of flu season. The two doses should be given at least 4 weeks apart.
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 will be 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.
Recommendations on the control and prevention of influenza are published annually, in late summer or early fall. Existing recommendations are available at Prevention and Control of Seasonal Influenza with Vaccines. New recommendations for the 2014-2015 season are available on the in the Morbidity and Mortality Weekly Report (MMWR).
Starting in 2014-2015, CDC recommends use of the nasal spray vaccine (LAIV) for healthy* children 2 through 8 years of age, when it is immediately available and if the child has no contraindications or precautions to that vaccine. Recent studies suggest that the nasal spray flu vaccine may work better than the flu shot in younger children. However, if the nasal spray vaccine is not immediately available and the flu shot is, children 2 years through 8 years old should get the flu shot. Don’t delay vaccination to find the nasal spray flu vaccine. For more information about the new CDC recommendation, seeNasal Spray Flu Vaccine in Children 2 through 8 Years Old or the 2014-2015 MMWR Influenza Vaccine Recommendations.
(*“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.)
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Flu vaccine is produced by private manufacturers, so supply depends on manufacturers. For this season, manufacturers have projected they will provide between 151-159 million doses of vaccine for the U.S. market.
Of the 151 million to 159 million doses of influenza vaccine projected to be available for the 2014-2015 season, manufacturers estimate that 78 million doses will be quadrivalent flu vaccine.
Flu vaccine is produced by private manufacturers, so the timing of vaccine availability depends on when production is completed. If everything goes as indicated by manufacturers, shipments may begin as early as July or August and continue throughout September and October until all of the vaccine is distributed.
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.
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 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.
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?
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.
It’s not possible to predict with certainty if the vaccine will be a good match for circulating viruses. The vaccine is made to protect against the flu viruses that research indicates will likely be most common during the season. However, 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.
Over the course of the flu season, CDC studies samples of circulating flu viruses to evaluate how close a match there is between viruses used to make the vaccine and circulating viruses.
One of the ways that helps CDC evaluate the match between vaccine viruses and circulating viruses is with a lab process called ‘antigenic characterization’. Results of antigenic characterization testing are published weekly in CDC’s FluView.
The match between the vaccine viruses and the circulating viruses is one factor that impacts how well the vaccine works.
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.
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.
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 will measure vaccine effectiveness in preventing laboratory-confirmed influenza among persons 6 months of age and older.
Information about vaccine supply is available on Preventing Seasonal Flu with Vaccination.
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).
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.
CDC will continue collecting and monitoring 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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