Vaccines are available to prevent influenza (See Viral Influenza Vaccines section in this report).
For mild influenza, symptom relief is similar to that for colds.
Who Needs Antiviral Drugs
Two classes of antiviral agents have been developed to treat influenza: neuraminidase inhibitors and M2 inhibitors. These drugs can shorten symptoms but there is no indication that they can prevent or reduce complications such as pneumonia. They do not help if they are started after the first 36 hours of illness. Because of emerging drug resistance, some experts suggest these drugs be reserved for severely ill patients or those at high risk.
Most people who get seasonal or H1N1 flu will likely recover without needing medical care. Doctors, however, can prescribe antiviral drugs to treat people who become very sick with the flu or are at high risk for flu complications.
If you need treatment for the flu, the CDC recommends that your doctor give you zanamivir (Relenza) or oseltamivir (Tamiflu). These drugs work best if you receive them within 2 days of becoming ill. You may get them later if you are very sick or if you have a high risk for complications.
Those at high risk for complications and are more likely to need treatment include:
- People with weakened immune systems, such as patients being treated for AIDS or cancer
- Elderly patients, particularly patients in nursing home
- Very young children (it may be difficult to tell whether pneumonia is related to influenza or caused by respiratory syncytial virus [RSV])
- Hospitalized patients and anyone with serious medical conditions, such as diabetes, heart, circulation, or lung disorders, particularly chronic lung disease
- Drug abusers who use needles
- Pregnant woman, especially those suspected of having H1N1 flu
To prevent infection with H1N1 flu, people who are at risk for complications and living in the same house as someone diagnosed with the virus should ask their doctor if they also need a prescription for these medicines.
Anti-Viral Drugs: Neuraminidase Inhibitors
Brands and Benefits. Zanamivir (Relenza) and oseltamivir (Tamiflu) are neuraminidase inhibitors. They are newer agents that have been designed to block a key viral enzyme, neuraminidase, which is involved with viral replication. While effective, their overall benefit is modest.
Important points about the use of these drugs:
- The main benefit of these drugs is a reduction in the length of symptoms by about one day, and only when started within 48 hours after symptoms become evident. They may be used for treating both A and B strains of influenza.
- They may help reduce transmission of the virus.
- Both show some benefits for preventing influenza. Only oseltamivir has been approved for this purpose, however, in people over the age of 1 year.
- They reduce complications of influenza, and decrease mortality when given within the first 4 days of onset of symptoms.
- Oseltamivir is the only drug studied in avian flu cases. Although it is active in lab experiments, it has not been successful clinically. Experience is very limited, however, and it is not clear whether people infected with avian flu received the drug in time for it to be useful.
Limitations and Side Effects. Although they have many advantages compared to the M2 inhibitors, neuraminidase inhibitors are much more expensive. They also need to be taken within 2 days of the start of symptoms to be effective. Neither neuraminidase inhibitor is effective against influenza-like illness (one that is not caused by an influenza virus). There are also some differences between the two drugs that could be significant for some individuals:
- Zanamivir is administered through an inhaler. People with asthma or other lung disorders may experience airway spasms and should use this drug with caution. Side effects are generally minor in most patients. It is important to make sure that elderly patients are able to properly use the zanamivir inhaler device. Zanamivir should ONLY be used in its original inhaler device.
- Oseltamivir comes in capsule and liquid form. Side effects are also minor, but about 10 to 15% of patients experience nausea and vomiting. Patients with kidney dysfunction should take lower doses.
Both drugs are approved for treatment in adult patients.
Children. Oseltamivir is approved for use in children 2 weeks and older for treatment. Studies report significant reduction in symptoms and in the incidence of ear infections in this population. The American Academy of Pediatrics recommends the following:
- Therapy should be provided to children with influenza infection who are at high risk of severe infection, and to children with moderate-to-severe influenza infection who may benefit from a decrease in the duration of symptoms.
- Prophylaxis should be provided (1) to high-risk children who have not yet received immunization and during the 2 weeks after immunization, (2) to unimmunized family members and health care professionals with close contact with high-risk unimmunized children or infants who are younger than 6 months, and (3) for control of influenza outbreaks in unimmunized staff and children in an institutional setting.
- Children aged 3 to 11 months who were born at full term may receive oseltamivir for prevention. The use of this medication for prevention of influenza in full term infants younger than 3 months of age is not recommended unless the situation is judged critical, such as a critically ill family member is hospitalized with the flu. Oseltamivir should not be given to preterm infants.
High-risk patients. Recent studies indicate neuraminidase inhibitors are safe and effective in patients with serious medical problems or other conditions that put them at risk for complications of flu.
A third neuroaminidase product, peramivir, is now in clinical trials. However, it was authorized as emergency treatment for severely ill, hospitalized patients with H1N1 "swine" flu. This authorization was terminated in June 2010. Peramivir is given intravenously.
Anti-Viral Drugs: M2 Inhibitors
Brands and Benefits. Amantadine (Symmetrel) and rimantadine (Flumadine) are M2 inhibitors. The following benefits may apply to the minority of strains of influenza A that remain sensitive to the drugs:
- Both offer some protection against influenza A and prevent severe illness if a person contracts the infection. (To be effective, it must be administered within 2 days of onset.)
- They may shorten the duration and lessen the severity of the flu if given within 48 hours of onset of symptoms.
Limitations. Drawbacks of M2 inhibitors include:
- They are not effective against the 2012 - 2013 flu strains.
- Viral resistance to these agents is rapidly increasing.
- M2 inhibitors are not effective against influenza B.
- Neither drug has proven to reduce the risk for complications of the flu, including pneumonia and bronchitis.
Side Effects. Both M2 inhibitors occasionally cause nausea, vomiting, indigestion, insomnia, and hallucinations. Amantadine affects the nervous system and about 10% of people experience nervousness, depression, anxiety, difficulty concentrating, and lightheadedness. Rimantadine is less likely to do so. Rarely, amantadine can cause seizures.
Note: Amantadine is a standard treatment for Parkinson's disease and should be continued for that condition.
"Flu Shots." These vaccines use inactivated (not live) viruses. They are designed to provoke the immune system to attack antigens found on the surface of the virus. (Antigens are foreign molecules that the immune system specifically recognizes as alien and targets for attack.)
Unfortunately, the antigens in these influenza viruses undergo genetic changes (called antigenic drift) over time, so they are likely to become resistant to a vaccine that worked in the previous year. Therefore, vaccines are redesigned annually to match the current strain.
- Influenza A. The influenza A virus is further categorized by primary molecular antigens (hemagglutinin and neuraminidase), which serve as the targets for the vaccines. Influenza A is a particular problem, because it can infect other species, such as pigs or chicken, and undergo major genetic changes.
- Influenza B viruses infect only humans and tend to be more stable than influenza A viruses, but they too vary. Although influenza B has been far less common than A, a vaccine for type B is important because experts are concerned that small children will not have developed any immunity to the virus, and will experience severe flu if they are exposed to type B viruses.
- Influenza C viruses infect humans. Like type B, it mainly affects young children and the illness is mild.
Traditional (trivalent) influenza vaccines match 2 current influenza A strains and 1 current influenza B strain. In December 2012, the FDA approved another type of influenza vaccine, which was available as an option for the first time in the 2013-2014 season. This vaccine, called quadrivalent, matches the 2 current strains of both influenza A and B, to provide wider protection. The vaccine is approved for ages 3 years and older.
Injectable vaccines. There are 3 types of influenza injectable vaccines:
- The regular killed vaccine is licensed for use in everyone 6 months and older.
- The intradermal injection (Fluzone Intradermal) uses a much smaller needle, and a smaller dose of the same killed vaccine. It is injected into the skin instead of the muscle.
- The high-dose injection (Fluzone High Dose) is for people 65 and older, whose immune system is possibly weaker as a result of normal aging. This killed vaccine is identical to the other two in the strains it carries, but delivers a much higher dose of the antigens, to create a strong immune response in the recipients.
Intranasal (inside the nose) vaccine. A live but weakened intranasal vaccine (FluMist) is effective and safe in healthy, non-pregnant people aged 2 to 49 years. It is known as a live, attenuated, intranasal influenza vaccine (LAIV). The vaccine is engineered to grow only in the cooler temperatures of the nasal passages, not in the warmer lungs and lower airways. It boosts the specific immune factors in the mucous membranes of the nose that fight off the actual viral infections. FluMist is given using a nasal spray. It should NOT be used in those who have asthma or in children under age 5 who have repeated wheezing episodes.
Flucelvax and Flublok are two new flu vaccines that are cell-based. This means the flu viruses in the vaccines are grown using cell culture technology instead of chicken eggs, which are used in the regular flu vaccine. Cell-based vaccines are made faster than traditional egg-based vaccines. Flucelvax can be received by persons 18 years and older. Flublok can be received by persons 18 through 49 years of age. Currently, there is no safety information about the two vaccines for pregnant or nursing women. Your health care provider can tell you if either vaccine is right for you.
Timing and Effectiveness of the Vaccine. Ideally, everyone should be vaccinated every September or October. However, it may take longer for a full supply of the vaccine to reach certain locations. In such cases, the high-risk groups should be served first.
Antibodies to the flu virus usually develop within 2 weeks of vaccination, and immunity peaks within 4 to 6 weeks, then gradually wanes.
- People should get vaccinated each year before flu season starts. One dose of the vaccine is needed. Children 2 through 8 years old who are getting a flu vaccine for the first time need two doses..
- It should be noted that if an individual develops flu symptoms and is accurately diagnosed in time, vaccination of the other members of the household within 36 to 48 hours affords effective protection to those individuals, according to an analysis of multiple studies.
In healthy adults, immunization typically reduces the chance of getting the seasonal flu by about 70 to 90%. The current flu vaccines may be slightly less effective in certain patients, such as the elderly and those with certain chronic diseases. Some evidence suggests, however, that even in people with a weaker response, the vaccine is usually protective against serious flu complications, particularly pneumonia. Some evidence also suggests that among the elderly, a flu shot may help protect against stroke, adverse heart events, and death from all causes.
Everyone aged 6 months and over should get a flu vaccine; the only exception is for those who are allergic to the vaccine. Vaccination is especially important in the following groups, who are at a high risk for complications from the flu:
- People who are 50 or more years of age
- People who are 6 to 49 months of age
- People who have chronic lung disease, including asthma and COPD, or heart disease
- People who are 18 years old or younger AND taking long-term aspirin therapy
- People who have sickle cell anemia or other hemoglobin-related disorders
- People who have kidney disease, anemia, diabetes, or chronic liver disease
- People who have a weakened immune system (including those with cancer or HIV/AIDS)
- People who receive long-term treatment with steroids for any condition
- Women who are pregnant or plan to become pregnant during the flu season. Women who are pregnant should receive only the inactivated flu vaccine. (Vaccinations should usually be given after the first trimester. Exceptions may be women who are in their first trimester during flu season, because their risk from complications of the flu is higher than any theoretical risk to the baby from the vaccine)
Possible side effects of the flu vaccine include:
- Allergic Reaction. Newer vaccines contain very little egg protein, but an allergic reaction still may occur in people with strong allergies to eggs. A new vaccine (Flucelvax) made in animal cell culture, not in eggs, was approved by the FDA for people aged 18 years and older.
- Soreness at the Injection Site. Up to two-thirds of people who receive the influenza vaccine develop redness or soreness at the injection site for 1 or 2 days afterward.
- Runny nose, nasal congestion, sore throat, fever with nasal spray vaccine.
- Flu-like Symptoms. Some people actually experience flu-like symptoms, called oculorespiratory syndrome, which include conjunctivitis, cough, wheeze, tightness in the chest, sore throat, or a combination. Such symptoms tend to occur 2 to 24 hours after the vaccination and generally last for up to 2 days. It should be noted that these symptoms are not the flu itself but an immune response to the virus proteins in the vaccine. (Anyone with a fever at the time the vaccination is scheduled, however, should wait to be immunized until the ailment has subsided.)
- Guillain-Barre Syndrome. This paralytic illness occurs in very rare cases.
There has been some question concerning influenza vaccinations because of reports that these vaccines may worsen asthma. Recent and major studies have been reporting, however, that the vaccination is safe for children with asthma. It is also very important for these patients to reduce their risk for respiratory diseases.
Avian Influenza Vaccine
The FDA approved the first vaccine for humans against H5NI influenza virus in April 2007. The vaccine, which is made from a human strain of the virus, could be used in people ages 18 to 64 to prevent the spread of the virus from human to human. The vaccine requires two doses, given about a month apart. It will not be sold commercially, but instead is being purchased by the U.S. government to be stockpiled and distributed to public health officials in the event of an outbreak of avian flu. The vaccine led to the development of antibodies in 45% of those who received the higher dose studied. The most common side effects reported were pain at the injection site, headache, and muscle pain. Research on the vaccine is continuing.
A new vaccine, currently in clinical trials, is made from artificial virus-like particles -- a collection of proteins that look like the outside of the virus but are made in the lab and cannot reproduce.
Who Needs Antibiotic
How Is Strep Throat Treated? Strep throat infections require antibiotics. Antibiotics prevent a serious complication called rheumatic fever, which can result in permanent damage to the heart. Fortunately, this complication rarely occurs in United States anymore. Antibiotic treatment of strep throat will almost always prevent this complication. In addition, antibiotics shorten the recovery time from strep throat.
The following antibiotics are generally used to treat strep throat:
- Penicillin is usually the antibiotic of choice unless the patient is allergic to it. A full 10 days of treatment may be necessary to clear the infection. Amoxicillin, a form of penicillin, is proving to be effective when taken in a single daily dose for 10 days.
- Macrolide antibiotics. Erythromycin is known as a macrolide antibiotic and is an appropriate choice for patients with penicillin allergies. A 10-day regimen is needed to clear the infection. The drug often causes gastrointestinal distress. Another macrolide, azithromycin, can be given as a single daily dose and is effective in 5 days. It has fewer side effects than erythromycin but is more expensive. Bacterial resistance to macrolides is increasing.
- Cephalosporins are also very effective in eradicating the bacteria. but they may cause reactions in people with severe penicillin allergies.
Antibiotics are often prescribed inappropriately for non-strep sore throats. Studies indicate that fewer than half of adults and far fewer of the children with even strong signs and symptoms for strep throat actually have strep infections.
Parents should be comforted that a delay in antibiotic treatment while waiting for lab results does not increase the risk that the child will develop serious long-term complications, including acute rheumatic fever. If a patient is severely ill, however, it is reasonable to begin administering antibiotics before the results are back. If the culture is negative (there is no evidence of bacteria), the doctor should call the family to make certain the patient stops taking the antibiotics and any remaining pills are discarded.
Children who have a sore throat and who have had rheumatic fever in the past should receive antibiotics immediately, even before culture results are back. Children with a sore throat who have a family member with strep throat or rheumatic fever should also receive immediate antibiotic treatment.
The intense and widespread use of antibiotics is leading to a serious global problem of antibiotic resistance. The inappropriate use of powerful newer antibiotics for conditions such as colds or sore throats poses a particular risk for the development of resistant strains of bacteria. For example, the number of cases of methicillin-resistant Staphylococcus aureus (MRSA) is increasing in people who have no known risk factors. (MRSA can cause severe skin infections.) In 2006, rates of Neisseria gonorrhoeae resistance to the fluoroquinolone antibiotics family exceeded 10%. The CDC no longer recommends treating gonorrhea infections with fluoroquinolone first.
When Antibiotics Are Needed for Upper Respiratory Infections.
Antibiotics do not affect viruses and, in healthy individuals, these drugs are not necessary or helpful for influenza or colds, even with persistent cough and thick, green mucus. In one disturbing study, antibiotics were prescribed for nearly half of children who went to the doctor for a common cold.
Antibiotics may be required for upper respiratory tract infections only under certain situations, such as the following:
- Patients, particularly small children or elderly people, who have medical conditions that put them at high risk for complications from any respiratory tract infections, may sometimes be given antibiotics.
- Patients with severe sinusitis that does not clear up within 7 days (some experts say 10 days) and whose symptoms include one or more of the following: green and thick nasal discharge, facial pain, or tooth pain or tenderness. [For more information, see In-Depth Report # 62: Sinusitis.]
- Some children with middle ear infections, although experts differ on who will benefit. Some experts recommend that only children under the age of 2 years should be treated with antibiotics, and children over 2 should be treated on a case-by-case basis. [For more information, see In-Depth Report # 78: Ear Infections.]
- Patients with strep throat or severe sore throat that involves fever, swollen lymph nodes, and absence of cough. (Strep throat makes up only 10 to 15% of all sore throat cases.)
Patients at Highest Risk for Infection with Resistant Bacteria Strains. Some patients are at greater risk for developing an infection resistant to common antibiotics. At this time, the average person is not endangered by this problem. Risk factors include:
- Very old or very young age
- Exposure to patients with drug-resistant infection
- Hospitalization in intensive care units
- History of an invasive surgical procedure
- Staying in the hospital
- Prolonged course of antibiotics, particularly within the past 4 to 6 weeks
- Serious wounds
- Tubes down the throat, catheters, or intravenous (I.V.) lines
Children at higher risk for antibiotic resistance are those who attend day care, who are exposed to cigarette smoke, who were bottle-fed, and who had siblings with recurrent ear infections.
What the Health Care Community Is Doing. Prescribing antibiotics only when necessary is the most important step in restoring bacterial strains that are susceptible to antibiotics. Encouraging studies are reporting that inappropriate antibiotic prescriptions are on the decline. Prescriptions for other common respiratory infections, such as otitis media, sore throat, acute bronchitis, and colds and flus have been decreasing.
What Patients and Parents Can Do. Patients and parents can also help with the following tips:
- Use home or over-the-counter remedies to relieve symptoms of mild upper respiratory tract infections.
- Realize that antibiotics will not shorten the course of a viral infection. It is important for patients and parents to understand that although antibiotics may bring a sense of security, they provide no significant benefit for a person with viral infection, and overuse can contribute to the growing problem of resistant bacteria.
- Don't pressure a doctor into prescribing an antibiotic if it is clearly inappropriate. The doctor very often will give in.
- If a child needs an antibiotic, ask the doctor whether it is appropriate to use high-dose short-term antibiotics, which may lower the risk for developing resistant strains.
- If an antibiotic is prescribed, take the full course, even if you feel better before finishing it.