Colds and Influenza (the Flu)

Description

Alternative Names

Medications

For mild influenza, symptom relief is similar to that for colds. Antiviral agents have now been developed to treat influenza A, B, or both. There are two classes of agents: M2 inhibitors and neuraminidase inhibitors. In addition vaccines are available to prevent influenza. In some cases the antiviral agents may also be used for prevention.

Anti-Viral Drugs: M2 Inhibitors

Brands and Benefits. Amantadine (Symmetrel) and rimantadine (Flumadine) are M2 inhibitors. They have the following benefits:

• Both offer protection against influenza A and prevent severe illness if a person contracts the infection. (To be effective it must be administered within two 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 the following:

• M2 inhibitors are not effective against influenza B. (Although less common than influenza A, type B may have a severe effect on some people, particularly on small children, who have not been exposed to this strain and so have not developed any immunity to it.)
• Viral resistance to these agents is rapidly emerging.
• Neither has proven to reduce the risk for complications, including pneumonia and bronchitis.

Side Effects. Both agents occasionally cause nausea, vomiting, and indigestion. Amantadine affects the nervous system and about 10% of people experience nervousness, depression, anxiety, difficulty concentrating, and lightheadedness. Rarely, amantadine can cause hallucinations and seizures, usually in elderly people already at risk for psychiatric symptoms.

Anti-Viral Drugs: Neuraminidase Inhibitors

Brands and Benefits. Zanamivir (Relenza) and oseltamivir (Tamiflu) are called neuraminidase inhibitors. They are newer agents that have been designed to block a key viral enzyme, neuraminidase, which is involved with viral replication.

Both zanamivir and oseltamivir have the following benefits:

• Neuraminidase inhibitors are effective for treating both A and B strains of influenza. (M2 inhibitors are only effective against type A.)
• They shorten the duration of the flu by one to three days.
• They may help reduce transmission of the virus, although evidence is needed to confirm these finding.
• They may have a lower risk than M1 inhibitors for emerging viral strains that are resistant to their effects.
• They have fewer serious side effects than the M2 inhibitors.
• Both have some benefits for preventing influenza. Only oseltamivir has been approved for this purpose, however, and only in people over 13.
• They may reduce complications of influenza, although this needs to be confirmed. It is not yet known if they have any effect on overall survival rates.

Limitations and Side Effects. Although they have many advantages compared to the M2 inhibitors, they are much more expensive. They also need to be taken within two days of symptoms to be effective. There are also some differences between the two agents that could be significant for some individuals:

• Zanamivir (Relenza) is administered as a nasal spray or 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. Of concern, however, was a 2001 British study, which found that a majority of elderly patients were not able to properly use the zanamivir (Relenza) inhaler device, making the medicine virtually ineffective in these cases. The study was small, however, and other reports suggest that zanamivir is sill effective in this older group.
• 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.

Candidates. Their current use in different age and patient groups are as follows:

• Adults. Both are approved for treatment in adult patients.
• Children. Oseltamivir is approved for use in children age one and older. Studies report significant reduction in symptoms and in the incidence of ear infections. Zanamivir is approved for children over seven, and studies are currently underway to determine its safety in younger children.
• High-Risk Patients. Recent studies indicate they are safe and effective in patients with serious medical problems or other conditions that put them at risk for complications of flu.

Viral Influenza Vaccines

Description of Vaccines. Vaccines against influenza employ inactivated (not live) viruses. They are designed to provoke the immune system to attack antigens contained on the surface of the virus. (Antigens are foreign molecules that the immune system specifically recognizes as alien and so targets for attack.)

Unfortunately, the antigens in these influenza viruses undergo genetic alterations (called antigenic drift) over time, so they are likely to become resistant to a vaccine that worked in the previous year. Vaccines are then 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 chickens, and undergo major genetic reassortments.
• Influenza B viruses 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.

A live but weakened intranasal vaccine (FluMist) is proving to be effective and safe in healthy people aged 5 to 49 years and has been approved by the FDA. 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 employed using a nasal spray and in one study provided protection against the flu in up to 93% of children.

Timing and Effectiveness of the Vaccine. Ideally, appropriate candidates should be vaccinated every October or November. 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 influenza virus usually develop within two weeks of vaccination, and immunity peaks within four to six weeks, then gradually wanes.

In healthy adults, immunization typically reduces the chance of illness 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. Even in people with a weaker response, however, the vaccine is usually protective against serious flu complications, particularly pneumonia. In fact, among the elderly, interesting studies are now suggesting that influenza vaccination may help protect against stroke, adverse heart events, and death from all causes.

Children Who Should Be Vaccinated. The following children over six months should be vaccinated against influenza:

• Any child with a condition that requires regular medical care or who has been hospitalized for a serious illness (particularly lung or kidney disease, diabetes, sickle-cell, or immune deficiencies). Vaccinations even in infants under six months old with certain conditions are warranted. In fact, in 2003 the American Academy of Pediatrics (AAP) and the CDC began recommending yearly influenza vaccination in all healthy children between six months and two years of age. Vaccination may even be warranted in some children below six months of age. This recommendation may vary from year to year depending on the supply of the vaccine. If parents are concerned about vaccines that contain the mercury preservative thimerosal, they can ask their doctor about reduced-thimerosal flu vaccine.
• Children who are receiving long-term aspirin therapy should also be immunized against the flu because they are at higher risk for Reyes syndrome, a life-threatening disease, if they get the flu.

Of note: There has been some question concerning influenza vaccinations because of some reports that 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. Still, 90% of asthma patients remain unvaccinated.

Older Children and Adults Who Should Be Vaccinated. The following, in order of priority, are the population groups who should be vaccinated each year. The first two groups have the highest need for influenza vaccinations and are given top priority:

• All adults 65 years and older. Vaccinated older adults have lower hospitalization rates than unvaccinated peers. Evidence now suggests that vaccination may help protect against adverse heart events (including after heart surgeries), stroke, and death from all causes in the elderly. Still, studies suggest that only two thirds of this group are vaccinated, mostly because of unwarranted fears of ineffectiveness or adverse effects.
• People of any age at high risk for serious complications from influenza. Such people include those with heart disease, lung problems, immune deficiencies, diabetes, kidney disease, or chronic blood disease. (There have been concerns about the safety of the vaccinations in certain high-risk patients such as those with HIV or asthma. Studies now suggest that the vaccine is generally safe in these patient groups. Furthermore, their risk for serious complications from influenza outweighs any potential adverse effects from the vaccines.)
• Adults between the ages of 50 and 64 who have chronic medical conditions. (The US Advisory Committee on Immunization Practices (ACIP) suggests that all adults over age 50 should be vaccinated, although this is not recommendation of the CDC.) People (such as household members or healthcare workers) in contact with individuals who are at high-risk for complications from influenza.

Other adults who should consider influenza vaccinations include the following:

• People at risk for complications for influenza and who are traveling to the tropics at any time or to the Southern Hemisphere between April and September.
• Pregnant women who are at risk for complications of influenza and who will be in their second or third trimester during flu season. (Vaccinations should usually be given after the first trimester. Exceptions may be women who are in their first trimester during flu season and their risk from complications of the flu is higher than any theoretical risk to the baby from the vaccine.)
• People such as firemen or policemen who are critical for public safety.

Negative Effects. Possible negative responses include the following:

• Allergic Reaction. Newer vaccines contain very little egg protein, but an allergic reaction still may occur in people with strong allergies to eggs.
• 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 one or two days afterward.
• Flu-like Symptoms. Some people actually experience flu-like symptoms, called oculo-respiratory syndrome, which include cough, wheeze, tightness in the chest, sore throat, or a combination. Such symptoms tend to occur between 2 and 24 hours after the vaccination and generally last up to two days. These symptoms are not influenza 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. Isolated cases of a paralytic illness known as Guillain-Barre syndrome occurred in about one of every 100,000 people vaccinated with the swine-flu vaccine in 1976, but it has not been a problem with subsequent vaccines.

Pneumococcal Vaccines

The pneumococcal vaccine protects against S. pneumoniae (also called pneumococcal) bacteria, the most common cause of respiratory infections. There are two effective vaccines available, one called a 23-valent polysaccharide vaccine (Pneumovax, Pnu-Immune) for adults and a 7-valent conjugate vaccine (Prevnar or PCV7) for infants and young children. Experts are now recommending that more people, including healthy elderly people, be given the pneumococcal vaccine, particularly in light of the increase in antibiotic-resistant bacteria. This has created a great sense of urgency in the medical community to find effective measures for preventing infection.

Pneumococcal Vaccine in Young Children. The pneumococcal vaccine (Prevnar or PCV7) is very effective in children. Evidence suggests that this vaccination, plus the vaccination against Haemophilus influenzae (an important cause of meningitis), has led to 25,000 fewer cases of serious bacterial infections each year.

The pneumococcal vaccine is now recommended by many experts for the following groups:

• All children up to age two. The pneumococcal vaccine (Prevnar or PCV7) has now been added to the Recommended Childhood Immunization Schedule. The pneumococcal vaccine (Prevnar or PCV7) is very effective in children. Studies are suggesting that it prevents common ear infections as well as serious infections, such as pneumonia. In one study, a similar vaccine under investigation protected not only children in day care from serious respiratory infections, but their younger unvaccinated siblings had fewer infections as well.
• Children up to age five who are at risk for pneumonia or complications of influenza, such as children with sickle disease, those with immune deficiencies, or children with chronic medical conditions.
• Other children age two to five who are higher risk for serious pneumococcal infections should be considered for vaccinations. They include African or Native Americans, children in group child care, socially or economically disadvantaged children, or those who have had frequent or complicated acute middle ear infections within the past year. (In one study, the vaccine reduced the number of ear infections episodes by 6%.)

The recommended schedule of immunization for Prevnar (PCV7) is four doses, given at 2, 4, 6, and 12 to 15 months of age. Infants starting immunization between 7 and 11 months should have three doses. Children starting their vaccinations between 12 and 23 months only need two doses. And those who are over two years old need only one dose.

Pneumococcal Vaccine in Older Children and Adults. The vaccine is proving to be effective in reducing the rate of pneumonia in young adults, although not to the degree that it protects young children. Its benefits for the elderly--other than protection against bloodstream infection--is unclear. Still, pneumonia is declining among adults, which may be due to fewer infections being transmitted from vaccinated young children. Many experts now recommend the vaccine for the following older children or adults:

• All people over 65 years old. (Anyone vaccinated more than five years previously should be revaccinated.) Of note, the vaccination is protective against pneumococcal bacteremia (invasive infection) in this group, but it does not appear to protect against community-acquired pneumonia itself.
• Adults with any chronic condition that increases the risk for pneumonia. This includes patients with heart disease (e.g., congestive heart failure, cardiomyopathies), chronic lung disease (COPD or emphysema, but not asthma), or diabetes.
• Individuals with immune deficiencies (e.g., HIV) or those undergoing treatments to suppress the immune system.
• Patients with autoimmune diseases, such as rheumatoid arthritis and lupus. Unfortunately, studies suggest the vaccine may not be as effective in these patients as those with healthy immune systems. Nevertheless they are at high risk for serious respiratory infections and should be vaccinated.
• Patients with kidney disease or kidney transplants. Older people who have had transplant operations or those with kidney disease may require a revaccination after six years.
• Patients with problems in the spleen.
• Alcoholics (especially those with cirrhosis).
• People living in long-term care facilities.
• Alaska Natives or American Indians, who may be at increased risk for pneumonia.

Because the vaccine is inactive, it is safe for pregnant women and people with immune deficiencies. In fact, when the vaccine is administered to pregnant women, it may actually protect their infants against certain respiratory infections.

Protection lasts for over six years in most people, although the protective value may be lost at a faster rate in elderly people than in younger adults. Anyone at risk for serious pneumonia should be revaccinated six years after the first dose, including those who were vaccinated before age 65. Subsequent booster doses, however, are not recommended.

Side Effects of the Pneumococcal Pneumonia Vaccine. Side effects include pain and redness at the injection site, fever, and joint aches. Children are more likely to have fever within 48 hours if they receive other vaccines at the same time and also after the second dose. Rarely, such local reactions can be severe. Even if a person is mistakenly re-vaccinated before the effects of the first vaccination have worn off, the risk for severe side effects is very low. Allergic reactions are very rare.