The study, funded by the flu maker MedImmune Inc out of Gaithersburg, MD showed that children who received the nasal spray vaccine were 55 percent less likely to experience lab-confirmed flu than children who received injected forms of the vaccine.

Flumist contains a live attenuated virus whereas the injected form of the vaccine contains an inactivated virus, which in part makes the difference in their efficacy. Early trials showed the flu vaccine in either form is able to reduce the flu cases by 87 percent.

The study involved 8,000 children ages from 6 to 59 months from 249 international sites located in the United States, Europe, Asia and the Middle East.

The participants, apparently healthy without a history of wheezing or severe asthma before entering the study, were randomly assigned Flumist or inactivated flu vaccines, Fluzone or Vaxigrip, depending upon the location between Oct. 20 and Oct. 29, 2004.

The researchers also found children who received Flumist experienced fewer cases of ear infection and other types of flu the vaccine is not intended to prevent.

"The nasal spray vaccine was significantly better at protecting children than the standard flu shot," Healthyday.com quoted study author Dr. Robert Belshe, director of the Center for Vaccine Development at Saint Louis University Medical Center, in St. Louis as saying.

Dr. Belshe said Flumist was more effective than the inactivated vaccines in the young age group because the live vaccine was sprayed directly into the nose and antibodies developed where they were needed most.

"The flu can be a very serious disease in young children and they're the major mechanism for transmitting flu," Belshe was quoted by healthday.com as saying. "The nasal spray vaccine is a significant advance in controlling flu in young children."

However, children who received the nasal spray vaccine, particularly those under the age of 12 months or younger were more likely to experience wheezing and to be hospitalized for any cause than those who received an injected form of the vaccine.   The wheezing problem was already observed in children younger than 5 in early trials.

The researchers don't know why these children were more vulnerable to wheezing and hospitalization.   But because of the potential wheezing risk, the nasal spray vaccine is not approved for children with asthma.

FluMist was approved on June 17, 2003 in the U.S. to prevent influenza illness due to influenza A and B viruses in healthy children and adolescents, ages 5-17 years, and healthy adults, ages 18-49.

But those who have immune suppression or a history of asthma and or wheezing or chronic underlying medical conditions that may predispose them to severe flu infections should not be given this nasal spray flu vaccine, according to the U.S. government.

Flumist has yet to be approved by the Food and Drug Administration for use in children under the age of 5 in the United States. The vaccine maker said that the results of the study could hopefully lead the FDA to approve the vaccine for the younger children.

For more information regarding the nasal spray flu vaccine, read below.

Questions & Answers: The Nasal-Spray Flu Vaccine (Live Attenuated Influenza Vaccine [LAIV])

What is the nasal-spray flu vaccine (or LAIV)?

The nasal-spray flu vaccine (sometimes called LAIV for Live Attenuated Influenza Vaccine) is a new flu vaccine that was licensed in 2003. It is different from the other licensed influenza vaccine (also called the "flu shot") because it contains weakened live influenza viruses instead of killed viruses and is administered by nasal spray instead of injection.

How does the nasal-spray flu vaccine (LAIV) work?

The nasal-spray flu vaccine contains three different live (but weakened) influenza viruses. When the viruses are sprayed into the nose, they stimulate the body's immune system to develop protective antibodies that will prevent infection by naturally occurring influenza viruses.

The live viruses in the nasal-spray flu vaccine (LAIV) are attenuated, cold-adapted, and temperature sensitive. What does this mean?

Attenuated means the viruses are weakened and will not cause severe symptoms often associated with influenza illness. Cold-adapted and temperature sensitive mean the viruses can grow in the nose and throat, but not in the lower respiratory tract where the temperature is higher.

How effective is the nasal-spray flu vaccine (LAIV)?

In one large study among children aged 15-85 months, the nasal-spray flu vaccine (LAIV) reduced the chance of influenza illness by 92% compared with placebo. In a study among adults, the participants were not specifically tested for influenza. However, the study found 19% fewer severe febrile respiratory tract illnesses, 24% fewer respiratory tract illnesses with fever, 23-27% fewer days of illness, 13-28% fewer lost work days, 15-41% fewer health care provider visits, and 43-47% less use of antibiotics compared with placebo.

Who can be vaccinated with the nasal-spray flu vaccine (LAIV)?

LAIV is approved for use in healthy people between the ages of 5 and 49 years.

Who should not be vaccinated with the nasal-spray flu vaccine (LAIV)?

    * People less than 5 years of age

    * People 50 years of age and over

    * People with a medical condition that places them at high risk for complications from influenza, including those with chronic heart or lung disease, such as asthma or reactive airways disease; people with medical conditions such as diabetes or kidney failure; or people with illnesses that weaken the immune system, or who take medications that can weaken the immune system.

    * Children or adolescents receiving aspirin

    * People with a history of Guillain-Barré syndrome, a rare disorder of the nervous system

    * Pregnant women

    * People with a history of allergy to any of the components of LAIV or to eggs

Should the nasal-spray flu vaccine (LAIV) be given to patients with chronic diseases other than those specifically listed above?

No. The nasal-spray flu vaccine is approved for use only in healthy people between the ages of 5 and 49 years.

Are there any contraindications to giving breastfeeding mothers LAIV (sold commercially as FluMist)?

Breastfeeding is not a contraindication for FluMist. See www.cdc.gov/mmwr/preview/mmwrhtml/rr5306a1.htm for a list of contraindications for FluMist.

Can the nasal-spray flu vaccine (LAIV) be given to patients when they are ill?

The nasal-spray flu vaccine (LAIV) can be given to people with minor illnesses (e.g., diarrhea or mild upper respiratory tract infection with or without fever). However, if nasal congestion is present that might limit delivery of the vaccine to the nasal lining, then delaying of vaccination until the nasal congestion is reduced should be considered.

Can people receiving the nasal-spray flu vaccine (LAIV) pass the vaccine viruses to others?

In clinical studies, transmission of vaccine viruses to close contacts has occurred only rarely. The current estimated risk of getting infected with vaccine virus after close contact with a person vaccinated with the nasal-spray flu vaccine is low (0.6%-2.4%). Because the viruses are attenuated and cold-adapted, infection is unlikely to result in influenza illness symptoms since the vaccine viruses have not been shown to mutate into typical or naturally occurring influenza viruses.

Can contacts of people with weakened immune systems get the nasal-spray flu vaccine (LAIV)?

People who are in contact with others with severely weakened immune systems when they are being cared for in a protective environment (for example, people with hematopoietic stem cell transplants), should not get LAIV. People who have contact with others with lesser degrees of immunosuppression (for example, people with diabetes, people with asthma taking corticosteroids, or people infected with HIV) can get LAIV.

What side effects are associated with the nasal-spray flu vaccine (LAIV)?

In children, side effects can include runny nose, headache, vomiting, muscle aches, and fever. In adults, side effects can include runny nose, headache, sore throat, and cough. Fever is not a common side effect in adults receiving the nasal-spray flu vaccine.

When should the nasal-spray flu vaccine (LAIV) be given?

The optimal time to receive influenza vaccine is usually in October or November. Children between the ages of 5 and 8 years who have never received influenza vaccine should receive the nasal-spray flu vaccine for the first time in October or earlier because they need a second dose 6 to 10 weeks after the first dose.

How often should the nasal-spray flu vaccine (LAIV) be given?

LAIV should be given each year before the influenza season.

Can people who received inactivated influenza vaccine (the flu shot) last year get the nasal-spray flu vaccine (LAIV) this year?

Yes, people who got inactivated influenza vaccine (the flu shot) last year can get the nasal-spray flu vaccine (LAIV) this year.

Can the nasal-spray flu vaccine (LAIV) be given at the same time as other vaccines?

An inactivated vaccine may be given either at the same time or at any time before or after the nasal-spray flu vaccine. A live vaccine may be given together with the nasal-spray flu vaccine. If the two live vaccines are not given at the same visit, they should be given more than 4 weeks apart.

Can the nasal-spray flu vaccine (LAIV) be used together with influenza antiviral medications?

If a person is taking an influenza antiviral drug (including Symmetrel [amantadine] for Parkinson's disease), then the nasal-spray flu vaccine should not be given until 48 hours after the last dose of the influenza antiviral medication was given. If a person has received the nasal-spray flu vaccine, an influenza antiviral medication should not be given until 2 weeks after the flu mist was administered.

If a child under the age of 9 years is getting influenza vaccine for the first time and requires 2 doses, does the same type of vaccine have to be used for both doses?

No, the first and second doses do not have to match; live or inactivated vaccine can be used for either dose. If inactivated influenza vaccine (the flu shot) is used first, then the nasal-spray flu vaccine (LAIV) should be given at least 4 weeks later. If the nasal-spray flu vaccine is used first, the second vaccine should be given 6 to 10 weeks later.

How is the nasal-spray flu vaccine (LAIV) stored?

The nasal-spray flu vaccine (LAIV) must be stored frozen at -15°C or colder. Any freezer (e.g., chest, frost-free) that reliably maintains an average temperature of -15°C and has a separate sealed freezer door is acceptable for storing LAIV. After thawing, the vaccine may be stored for up to 60 hours prior to use in a refrigerator at 2-8°C, and it should not be refrozen. Vaccine thawed for more than 60 hours should be discarded.

What personal protective equipment is recommended for health-care workers who are giving LAIV?

Personal protective equipment (gloves and masks) are not required for health-care workers administering LAIV.

Does the nasal-spray flu vaccine (LAIV) contain thimerosal?

No, the nasal-spray flu vaccine (LAIV) does not contain thimerosal or any other preservative.

Page last reviewed October 10, 2006

http://www.cdc.gov/flu/about/qa/nasalspray.htm