Catch the fever: It'll help you fight off infection

Public release date: 1-Nov-2011

Contact: Cody Mooneyhan
cmooneyhan@faseb.org
301-634-7104
http://www.faseb.org/">Federation of American Societies for Experimental Biology

Catch the fever: It'll help you fight off infection

New research published in the Journal of Leukocyte Biology demonstrates that elevated body temperature plays a vital role on the generation of effective T-cell mediated immune response

Bethesda, MD—With cold and flu season almost here, the next time you're sick, think twice before taking something for your fever. That's because scientists have found more evidence that elevated body temperature helps certain types of immune cells to work better. This research is reported in the November 2011 issue of the Journal of Leukocyte Biology (https://www.jleukbio.org).

"An increase in body temperature has been known since ancient times to be associated with infection and inflammation," said Elizabeth A. Repasky, Ph.D., a researcher involved in the work from the Department of Immunology at the Roswell Park Cancer Institute in Buffalo, New York. "Since a febrile response is highly conserved in nature (even so-called cold blooded animals move to warmer places when they become ill) it would seem important that we immunologists devote more attention to this interesting response."

Scientists found that the generation and differentiation of a particular kind of lymphocyte, known as a "CD8+ cytotoxic T-cell" (capable of destroying virus-infected cells and tumor cells) is enhanced by mild fever-range hyperthermia. Specifically, their research suggests that elevated body temperature changes the T-cells' membranes which may help mediate the effects of micro-environmental temperature on cell function. To test this, researchers injected two groups of mice with an antigen, and examined the activation of T-cells following the interaction with antigen presenting cells. Body temperature in half of the mice was raised by 2 degrees centigrade, while the other half maintained a normal core body temperature. In the warmed mice, results showed a greater number of the type of CD8 T-cells capable of destroying infected cells.

"Having a fever might be uncomfortable," said John Wherry, Ph.D., Deputy Editor of the Journal of Leukocyte Biology, "but this research report and several others are showing that having a fever is part of an effective immune response. We had previously thought that the microbes that infect us simply can't replicate as well when we have fevers, but this new work also suggests that the immune system might be temporarily enhanced functionally when our temperatures rise with fever. Although very high body temperatures are dangerous and should be controlled, this study shows that we may need to reconsider how and when we treat most mild fevers."

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

• People less than 2 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 <5 years old with a history of recurrent wheezing
• Children or adolescents receiving aspirin
• Pregnant women
• People who have a severe allergy to chicken eggs or who are allergic to any of the nasal spray vaccine components.
• People with a history of Guillain–Barré Syndrome (a severe paralytic illness, also called GBS) that occurred after receiving influenza vaccine and who are not at risk for severe illness from influenza should generally not receive vaccine. Tell your doctor if you ever had Guillain-Barré Syndrome. Your doctor will help you decide whether the vaccine is recommended for you.

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Influenza (live) vaccine side-effects

What are the risks from LAIV?

A vaccine, like any medicine, could possibly cause serious problems, such as severe allergic reactions. The risk of a vaccine causing serious harm, or death, is extremely small.

Live influenza vaccine viruses very rarely spread from person to person. Even if they do, they are not likely to cause illness.

LAIV is made from weakened virus and does not cause influenza. The vaccine can cause mild symptoms in people who get it (see below).

Mild Problems
Some children and adolescents 2-17 years of age have reported:

• runny nose, nasal congestion or cough
• headache and muscle aches
• fever
• wheezing
• abdominal pain or occasional vomiting or diarrhea

Some adults 18-49 years of age have reported:

• runny nose or nasal congestion
• sore throat
• cough, chills, tiredness/weakness
• headache

Severe Problems

• Life-threatening allergic reactions from vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the vaccination.
• If rare reactions occur with any product, they may not be identified until thousands, or millions, of people have used it. Millions of doses of LAIV have been distributed since it was licensed, and the vaccine has not been associated with any serious problems.

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The following groups should not receive the nasal spray vaccine (LAIV):

• Adults 50 years of age and older or children from 6 through 23 months of age. (Children younger than 6 months should not get either influenza vaccine.)


• People who have ever had a severe allergic reaction to eggs. People who have had a mild reaction to egg—that is, one which only involved hives—may receive TIV (not LAIV) with additional precautions. Make sure your healthcare provider knows about any allergic reactions.


• People who have had a severe reaction to the vaccine in the past.


• People with asthma and children younger than 5 years with one or more episodes of wheezing within the past year.


• Pregnant women.


• Anyone with certain muscle or nerve disorders (such as seizure disorders or cerebral palsy) that can lead to breathing or swallowing problems.


• Anyone with a weakened immune system.


• Anyone in close contact with someone whose immune system is so weak they require care in a protected environment (such as a bone marrow transplant unit). Close contacts of other people with a weakened immune system (such as those with HIV) may receive LAIV. Healthcare personnel in neonatal intensive care units or oncology clinics may receive LAIV.


• Children or adolescents on long-term aspirin treatment.


• People with a history of Guillain–Barré Syndrome (a severe paralytic illness, also called GBS) that occurred after receiving influenza vaccine and who are not at risk for severe illness from influenza should generally not receive vaccine. Tell your doctor if you ever had Guillain-Barré Syndrome. Your doctor will help you decide whether the vaccine is recommended for you.


• Your doctor will help you decide whether the vaccine is recommended for you.


• Tell your doctor if you have gotten any other vaccines in the past 4 weeks.


• Anyone with a nasal condition serious enough to make breathing difficult, such as a very stuffy nose, should get the flu shot instead.


• People who are moderately or severely ill should usually wait until they recover before getting flu vaccine. If you are ill, talk to your doctor about whether to reschedule the vaccination. People with a mild illness can usually get the vaccine.

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