Prevention

Viral Influenza Vaccines (Flu Shot)

Description of Vaccines. Vaccines against the flu (or a "flu shot") use 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 and 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 changes.
• 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) for healthy people aged 5 to 49 years is approved by the FDA. It is known as a live, attenuated, trivalent, 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 a nasal spray. In one study it protected up to 93% of children against the flu.

Timing and Effectiveness of the Vaccine. Ideally, people should get a flu shot 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. Immunity peaks within four to six weeks, then gradually wears off. That is why most people should get a flu shot every year.

In healthy adults, the flu shot reduces the chance of illness by about 70 - 90%. The current flu vaccines may be slightly less effective in the elderly and those with certain chronic diseases. But, even in people with weak immune systems, 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 American Academy of Pediatrics (AAP) and the CDC recommend flu shots for all healthy children between 6 and 23 months of age. (The flu shot is not approved for children less than 6 months of age.)

In addition, any child over the age of 2 years who has a condition that requires regular medical care or who has been hospitalized for a serious illness (particularly lung or kidney disease, diabetes, sickle cell anemia, or immune deficiencies) should also receive a flu shot. Children who are receiving long-term aspirin therapy should also be immunized against the flu because they are at higher risk for Reye's syndrome, a life-threatening disease, if they get the flu.

Children with Asthma. Recent and major studies have found that the flu shot is safe for children with asthma. It is 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. Older adults who receive a flu shot have lower hospitalization rates than those who don't. 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.

Other adults who should consider influenza vaccinations include:

• People at risk for flu complications 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 flu complications who will be in their second or third trimester during flu season. (Vaccinations should usually be given after the first trimester.)
• Health care providers with direct patient contact, child care providers, and residents of long-term care facilities should also be vaccinated.

Side Effects. Possible side effects include:

• 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, wheezing, tightness in the chest, and sore throat. Such symptoms tend to occur between 2 and 24 hours after the vaccination and generally last up to two days. 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. Isolated cases of 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. Guillain-Barre disease can cause paralysis.

Pneumococcal Vaccines

The pneumococcal vaccine protects against S. pneumoniae 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 another called 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.

Click the icon to see an image of pneumococcal pneumonia.

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 help reduce 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, are unclear. Still, pneumonia is declining among adults, which may be due to fewer infections 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.) The vaccination is protective against pneumococcal bacteremia (blood 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, chronic lung disease (COPD or emphysema, but not asthma), or diabetes.
• Individuals with immune deficiencies, such as 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 it is in 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 it may wear off faster 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. Pain and redness at the injection site, fever, and joint aches are possible with the pneumococcal vaccine. Children are more likely to have fever side effects within 48 hours if they receive other vaccines at the same time. They are also likely to have fewer side effects after the second dose. In rare cases, 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.