The earliest vaccine shipments came in the form of a nasal spray, which is now a priority for health care workers and children. The number of children who have died of the new virus climbed rapidly to 76 this week, already nearing the 88 child deaths for the entire 2007-8 flu season. A flu shot form of the vaccine is expected next week.
Web sites and talk shows are abuzz with worries that the government rushed the vaccine. The comedian Bill Maherrecently told his 60,000 Twitter followers that people who took flu shots were “idiots.” Consumer Reports recently released a poll showing that only 35 percent of parents surveyed would definitely have their children vaccinated. Undecided parents said they worried that the vaccine was new and untested.
So what are the facts? Here are answers to some commonly asked questions about the new flu virus, regular seasonal flu and the two flu vaccines intended to prevent them both. Join the discussion at nytimes.com/well.
Q:
What’s the difference between the seasonal flu that occurs every winter and this new H1N1 flu virus?
A:
Seasonal flu comes back in slightly different forms each year. But the H1N1 2009 is an entirely new combination of four genetic elements: a bird flu, some human flu genes and two types of swine flu. The H1N1 2009 virus, which has spread worldwide, was surprisingly robust during the spring and summer months. Right now, about 90 percent of the circulating flu is H1N1, although seasonal flu, which typically peaks in winter, has also been detected.
Q:
What is the difference between the two flu vaccines?
A:
The H1N1 2009 vaccine contains only the novel H1N1 virus. This year’s seasonal vaccine contains three influenza viruses — one A (H3N2) virus, one regular seasonal A (H1N1) virus unrelated to the swine flu strain and one B virus.
Q:
I’ve heard that the new flu strain circulating this fall is mild. Why should I have my child vaccinated?
A:
When it became clear last spring that the pandemic H1N1 strain would not be as deadly as once feared, health officials reassured a nervous public that most H1N1 infections had been “relatively mild.” It created the false perception that H1N1 is not a life-threatening illness. While most people who get H1N1 are sick for three or four days and then recover, a recent New England Journal of Medicine study showed that among Americans hospitalized with swine flu last spring, one in four ended up in intensive care and 7 percent of them died. In the Southern Hemisphere, 14 percent of flu patients in intensive care died.
Since Aug. 30, at least 936 Americans have died of flu symptoms or flu-associatedpneumonia, and it appears H1N1 2009 flu will be at least as deadly as seasonal flu, which kills about 36,000 people annually.
Q:
How is this flu season different from every other flu season?
A:
The new flu strain is preying on children and young adults and appears to have a disproportionately high fatality rate in pregnant women. Older people, typically most vulnerable to flu, appear to have some immunity. Since April, 76 children have died of H1N1, including 19 last week, according to the federal Centers for Disease Control and Prevention. During the first four months of the outbreak, 100 pregnant women were hospitalized with the virus, and 28 died. The C.D.C. reports that 37 states now have widespread influenza activity, highly unusual this early in the season. Hospitalization rates for influenza also are higher than expected for this time of year.
Q:
Since the vaccine for H1N1 is new, how do I know it is safe?
A:
Every year, the seasonal flu vaccine is tailored to match the viruses circulating at the time, and the H1N1 vaccine was made exactly the same way.
Q:
Was the H1N1 vaccine subjected to the same testing and clinical trials as seasonal flu vaccine?
A:
The F.D.A. does not require a new round of human clinical trials to study minor changes in the flu vaccine each year. However, clinical trials were conducted on the H1N1 2009 vaccine to determine the adequate dose. In addition, because H1N1 is a pandemic, we now have more information from other countries. Of the first 39,000 Chinese to get shots, only four had side effects, including muscle cramps and headaches. “You could argue that this is better tested than seasonal flu vaccine,” said Dr. Paul A. Offit, chief of infectious diseasesfor Children’s Hospital of Philadelphia.
Q:
Were manufacturing shortcuts taken to rush this vaccine to market?
A:
Secretary of Health and Human Services Kathleen Sebelius has lauded the government’s quick response to the pandemic threat and the fast turnaround of the new vaccine. That has created perceptions that the vaccine was rushed. The reality is that in 2005, worries of a bird flu epidemic prompted the Bush administration to increase flu vaccine production capacity. It typically takes five to six months to make flu vaccine, and that is about how long it took to produce the H1N1 2009 vaccine. The H1N1 virus itself grows more efficiently than some past flu strains. “We have cut no corners,” Dr. Thomas R. Frieden, the C.D.C. director, said at a news conference. “This flu vaccine is made as flu vaccine is made each year, by the same companies, in the same production facilities with the same procedures, with the same safety safeguards.”
Q:
How is flu vaccine made?
A:
The C.D.C. identifies and tests a viral strain, then distributes a version of it to vaccine manufacturers, who inject it into millions of eggs, where it multiplies. Then the virus is harvested, purified and developed into a vaccine.
Q:
What is the difference between the nasal spray and the flu shot?
A:
The injectable vaccine or flu shot is made from a killed influenza virus that is highly purified and broken into tiny pieces. It cannot recombine in the body to produce flu, but it can still stimulate the immune system to evoke a protective response.
The nasal vaccine, called FluMist, is made of an attenuated live virus. This is a weakened version of the virus that has been tamed in the laboratory so it cannot cause illness. (Themeasles and chicken pox vaccines also are made from a live attenuated virus.) The attenuated virus can multiply only in the cooler temperatures of the nasal passages, and cannot survive in the higher temperatures of the respiratory tract, said Dr. William Schaffner, chairman of the department of preventive medicine at Vanderbilt UniversitySchool of Medicine. When the vaccine is sprayed into the nose, it multiplies on the mucous membranes in the nose and throat, triggering the body’s immune response without causing any illness. Some studies suggest the nasal mist is more effective than the traditional flu shot.
FluMist is not approved for people with asthma, pregnant women or people with underlying medical problems like heart disease and diabetes.
Q:
How long after vaccination does the body develop immunity to the H1N1 2009 virus?
A:
In general, immunity to H1N1 2009 kicks in about seven to eight days after the vaccine, slightly faster than the 10 to 14 days typical of seasonal flu vaccine. However, a child below the age of 10 will need two doses of the H1N1 vaccine, spaced about a month apart, and full immunity will not occur until about a week after the final dose. “Kids get two doses because they don’t develop as high of a protective antibody response from the first dose,”
said Dr. Gregory A. Poland, an infectious disease specialist at the Mayo Clinic in Rochester, Minn.
Q:
Can seasonal flu vaccine and H1N1 2009 vaccine be taken at the same time?
A:
It depends on the formulation. A patient can receive two flu shots or a combination of nasal spray and flu shot. But patients who want both vaccines in nasal spray form must wait at least two weeks between vaccinations so the attenuated viruses do not compete against each other.
Q:
If I’ve already had the flu this year, do I need either flu shot?
A:
Unless your case was officially confirmed by a laboratory test as H1N1 2009, there is no way to be sure you are protected. If you did have confirmed H1N1, you are still vulnerable to seasonal flu.
Q:
Can you get vaccinated against flu if you have a fever or a cold?
A:
The flu vaccine is typically not recommended for patients with any signs of illness, so that symptoms are not wrongly misdiagnosed as side effects of a flu shot.
Q:
Can people who are allergic to eggs get the flu vaccine?
A:
The vaccine typically is not given to people with egg allergy. People at high risk for flu complications may be able to work with an allergist to be desensitized so they tolerate the vaccine.
Q:
Why are pregnant women at higher risk of complications from H1N1 flu?
A:
A woman’s immune system is compromised during pregnancy. Late in the pregnancy, the fetus pushes up against the thoracic cage and decreases a woman’s lung capacity, putting her at risk for respiratory complications if she contracts flu. A New England Journal study found that pregnant women with swine flu were nine times more likely to be in intensive care.
Q:
Is flu vaccination an option for people with suppressed immune systems?
A:
A flu vaccine works by stimulating the body’s immune system to produce antibodiesagainst the virus. A person with a suppressed immune system cannot generate an immune response and does not benefit from vaccination. This includes many cancer patients undergoing chemotherapy, asthma patients who require large doses of steroids and those taking immune-suppressing drugs after an organ transplant. Patients who are immune-compromised should talk to their doctor about whether they should get a flu shot.
Q:
Do adjuvants added to flu vaccine increase risk of an autoimmune reaction?
A:
This is a myth perpetuated on some health Web sites. Although substances called adjuvants are sometimes added to vaccines to make them more effective, no flu vaccine sold in the United States, including the H1N1 2009 vaccine, contains any adjuvants.
Q:
Does the new vaccine contain the mercury compound thimerosal?
A:
Flu vaccine packaged in a multidose vial contains thimerosal, a preservative that prevents contamination of the vial during repeated use. One dose from a multiuse vial contains about 25 micrograms of mercury. By comparison, a tuna fish sandwich contains about 28 micrograms of mercury. Repeated studies have shown thimerosal to be safe. However, people who want to minimize mercury exposure can ask for a vaccine in a single-dose package, which has only trace amounts. Thimerosal is not used in the production of FluMist.
Q:
What about the severe complications associated with the 1976 swine flu vaccine?
A:
A 1976 swine flu vaccine was associated with Guillain-Barré syndrome (pronounced ghee-YAN bah-RAY), in which the body damages its own nerve cells, causing weakness and sometimes paralysis. The data on flu vaccine and Guillain-Barré syndrome are not conclusive. One study suggested the 1976 vaccine posed a 1 in 100,000 risk. Another study found flu vaccine in general carries a 1 in one million risk for Guillain-Barré syndrome. By comparison, 1 in 8,300 Americans dies of flu each year.
Q:
If I think I have H1N1 2009, should I see a doctor?
A:
Most people will recover without needing a doctor. High-risk patients should see a doctor at the onset of flu symptoms and may be treated with the antiviral drug Tamiflu.
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