Avoiding The Flu, Part 2

by Food and Drug Administration (FDA)

(Page 2 of 2)

Drugs Help Some People

For these individuals, and persons expected to develop low levels of antibodies in response to the influenza vaccine because they have impaired immune systems, influenza-specific anti-viral drugs can be used for prevention during the flu season or after infection to relieve influenza symptoms.

The anti-viral agents Symmetrel (amantadine), approved by FDA in 1976, and Flumadine (rimantadine), a chemically similar drug approved by FDA in September 1993, are safe and effective in preventing signs and symptoms of infection caused by various strains of the influenza A virus in children over 1, healthy adults, and elderly patients. These drugs may also be used for family members or close contacts of influenza A patients and for elderly nursing home patients who have been vaccinated but may need added protection. When a vaccine is expected to be ineffective because an epidemic is caused by strains other than those covered by the vaccine, anti-viral drugs may be used to provide protection against infection.

Either drug may be used following vaccination during a flu epidemic to provide protection during the two- to four-week period before antibodies develop. If an adult has already come down with the flu, treatment with Symmetrel or Flumadine has been shown to reduce symptoms and shorten the illness if administered within 48 hours after symptoms appear. Children with the flu can be treated with Symmetrel

About 5 to 10 percent of people who take Symmetrel experience nausea, dizziness and insomnia. There have been reports of more serious neurological adverse events, including seizures and aggravations of psychiatric illnesses. Flumadine has similar side effects, but at a lower rate.

Though many flu victims use over-the-counter preparations, such as decongestants and fever reducers, to make them feel more comfortable, none of these products affects the course of the disease.

Prevention Worthwhile

Every year, about 20 percent of the U.S. population may become infected with flu, although each flu season is different. About 1 percent of those infected will require hospitalization because of complications, mostly bacterial pneumonia. Among those hospitalized, as many as 8 percent may die — about 20,000 people in an average year. But the 1957-1958 "Asian flu" caused 70,000 deaths, and the 1968-1969 "Hong Kong flu" carried off 34,000 persons. The toll is usually greatest among the elderly.

The economic costs run high, too. From 15 million to 111 million workdays are lost each year, depending on the severity of the epidemic. Added to that are the costs of over-the-counter and prescription medicines, physician visits, hospitalization, and lost productivity.

It's no contest between the cost of a flu shot and the physical and other costs exacted by a bad case of the flu. A yearly vaccination early in the flu season is the best way to avoid this miserable disease.

This Year's Vaccine

FDA's Vaccines and Related Biologicals Advisory Committee meets in late January each year to decide which strains of influenza virus should be incorporated into the vaccine for the coming flu season, based on reports from national and international surveillance systems. A World Health Organization panel meets in Geneva in mid-February to make final recommendations for the next season's flu vaccine.

The vaccine choices for the United States take into consideration the predominant strain(s) circulating among the population in the current season (November, December, January) and any "new" strains that may have appeared both here and in other parts of the world. Another important part of the decision process is the examination of antibody levels in people vaccinated with the current year's vaccine to determine if they had a good immune response. Equally important is examining antibody levels in the same people to see if the vaccine offered any protection against recently identified "new" strains.

"You have to make this decision [about which strains to include in the vaccine] a year in advance before the flu season starts," says Helen Regnery, Ph.D., chief, strain surveillance section, influenza branch, national Centers for Disease Control and Prevention. "There is an inherent problem; FDA's advisory committee must decide for a future event, based on past and current knowledge of circulating strains, as well as the appearance of new strains of influenza."

Flu viruses are divided into three types — A, B and C — though the C type is not common. Influenza A viruses cause the most severe and widespread outbreaks, while influenza B causes limited, milder illness.

Influenza A viruses are classified into subtypes on the basis of two surface antigens (substances that induce antibody formation) called hemagglutinin (H) and neuraminidase (N). Currently, the circulating subtypes of influenza A that have been identified as causing extensive human illness are influenza A (H3N2) and influenza A (H1N1). Influenza A (H3N2) viruses have been much more prevalent than influenza A (H1N1) during the last five years.

"Last year's flu season [1993-1994] was more severe than average," says Nancy Arden, chief, influenza epidemiology, CDC. "More than 99 percent of the influenza viruses isolated and characterized were type A(H3N2) and most were similar to the A/Beijing/32/92 strain. Although people of all ages are susceptible to type A(H3N2), compared with influenza type A (H1N1) and type B, the A(H3N2) viruses are associated with more illness, complications and deaths among the elderly."

The 1993-1994 influenza season began in November 1993 and peaked in late December 1993 and early January 1994. By early March, influenza activity was undetectable or had declined to very low levels in most of the United States. As in other seasons when the A(H3N2) strains have predominated, the proportion of influenza-associated deaths was higher than average. Although it is still too early to estimate the actual number of such deaths during the 1993-1994 season, normally about 90 percent of these deaths occur among people 65 and older.

The trivalent influenza vaccine prepared for the 1994-1995 flu season will include A/Texas/36/91 (H1N1), A/Shangdong/9/93 (H3N2), and B/Panama/45/90, differing from the 1993-1994 vaccine only in the H3N2 component, which was A/Beijing/32/92 last season. The geographic name represents the place where the strain was isolated.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.