Itâ€™s the middle of summer and right now you may be thinking more of allergies and sunburn than the flu. Think again.
This year, public health officials lowered the recommended age for getting a flu shot from 65 to 50 years old. But instead of rushing to open more vaccination clinics, theyâ€™re preparing for a shortage of available vaccine, which itself will be delayed. As a result, health officials around the country are planning to urge healthy people to put off or even skip their flu shots this year.
A shot in the dark
"Generally, weâ€™ll expect something like upwards of 80 million to 100 million doses, but we anticipate that this year weâ€™re probably going to fall short maybe by as many as 30 to 40 million doses," warns Fernando A.Guerra, director of the San Antonio Metropolitan Health District.
Each spring, based on global virus surveillance, health officials try to predict the three most dominant strains of flu for the coming season so that they know which types should be used to develop vaccines. But scientists say the current shortfall highlights the challenge of mass-producing vaccines against viruses that constantly mutate.
|Eggs are inoculated with the virus...|
image: Wyeth-Ayerst Laboratory
The viruses are normally grown in chicken eggs, harvested, and then killed through chemical means. The resulting vaccine is then purified and tested for safety and its effectiveness in stimulating antibodies. If a chosen strain canâ€™t be grown in eggs, then a close match is selected that can. But this process doesnâ€™t happen overnight. The strains normally take four to five months to grow before they can be inactivated and processed.
There are three types of influenza—types A, B, and C—but types A and B are the most dangerous. The three strains that were chosen for the 2000-01 flu season are A/Panama, A/New Caledonia and B/Yamanashi. However, the A/Panama strain has grown more slowly than expected. "Itâ€™s certainly a combination of the viral strains that are being isolated," says Guerra. "Theyâ€™re certainly not able to assure the development in culture of that particular viral strain."
To make matters worse, two of the four companies that manufacture the U.S. flu vaccine—Parkedale Pharmaceuticals and Wyeth-Ayerst Laboratories— have had technical problems with processing and testing this yearâ€™s vaccine.
|...then the viruses are harvested to create the vaccine.|
image: Wyeth-Ayerst Laboratory
In March, the FDA sent a letter to Parkedale Pharmaceuticals citing manufacturing deficiencies for the flu vaccine, including problems with contamination and potency. It was the third such notice sent to the company in seven months, but this one ordered Parkedale to stop manufacturing the vaccine until the problems could be addressed. Parkedale has since been working closely with the FDA to resolve the situation. The company is optimistic that it will be able to move forward with manufacturing the vaccine, although the timeline is not certain, according to Kyle Maccione, executive vice president.
But because manufacturing a flu vaccine is complicated, snags may be inevitable. "Youâ€™re dealing with a living organism," notes Tom Lupold , associate director of influenza vaccine manufacturing at Wyeth-Ayerst. "Itâ€™s not always predictable." Wyeth-Ayerst says it is committed to producing the same amount of vaccine it delivered last year—27 million doses.
Its a race against time, however. Production on one strain of the virus begins in January, but because new strains are picked up rapidly, the final selection of the other two strains is put off, according to Lupold. "So theyâ€™re forced to make the decision in late March for a trivalent vaccine," he explains. "Meanwhile, there can be up to a dozen candidates."
Dealing with delays
While there may not be a crisis looming on the horizon, according to Guerra, there will be a delay this fall in providing flu shots to the general public. "It will more than likely have to be done in a prioritized schedule so that we really target the groups that are at the greatest risk initially and then begin to phase in the other groups as the season progresses," he says.
The Advisory Committee on Immunization Practices (ACIP), which is responsible for vaccine guidelines, has urged health care providers to begin thinking now about delaying mass vaccination campaigns until November. Normally vaccinations are recommended to begin in October, but can be given anytime during the winter. If the shortfall is severe, the ACIP and the Centers for Disease Control and Prevention would modify the recommendations for the 2000-01 season so that those facing the highest risk of death would be vaccinated first. Health officials should have a much better idea of how many doses will be available in about a month.
A touch of the flu
Flu is a major cause of illness and death in the U.S., leading to approximately 20,000 deaths and more than 110,000 hospitalizations each year, according to the CDC.
Travelers should note that while the flu is generally prevalent in the Northern Hemisphere during the winter months, its peak activity south of the equator is from April through September.
The CDC recommends getting a flu shot two weeks before departure to: anyone traveling to the tropics; anyone traveling with large tour groups at any time of year; travelers who were not vaccinated during the most recent fall/winter and are at high risk for complications from the flu.
Itâ€™s not known if revaccination before summer travel is effective for those who were already vaccinated the previous winter.
For more information, see Travelerâ€™s Health Information on Influenza from the CDC.
Although there is a misconception that the flu vaccine is not very effective, the opposite can be true. Sometimes people think the shot hasnâ€™t worked because they subsequently develop a respiratory virus and mistake it for the flu. Studies of healthy young adults have shown the vaccine to be 70 to 90 percent effective in preventing illness, however. In elderly patients who are not in nursing homes, the vaccine has been shown to reduce hospitalization by about 70 per cent.
It takes about a week or two after being vaccinated to develop antibodies to the flu. Prior to the 1970s, flu vaccines sometimes caused low grade fever and other side effects, but today, the most common side effect is arm soreness and swelling at the site of injection. In 1976, swine flu vaccine was associated with an increased number of cases of Guillain-Barré syndrome, which causes paralysis. But the risk is only estimated to be one or two cases per million people vaccinated.
Scientists are always looking for new ways to make and deliver the flu vaccine. Research has been done using a flu vaccine in the form of a nasal spray, as well as a genetic-based vaccine, where part of the virusâ€™s genetic code would be inserted into a few cells in the body to stimulate antibody production. Until such efforts pan out, however, Americans remain dependent on the current method of making flu vaccine each year. Elsewhere on the web:
Antiviral flu drugs
Flu basics from the CDC
U.S. flu seasons 1995-2000
Information on influenza from the American Lung Association
Clinical Features and History of Influenza
FluNet from the World Health Organization