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How safe are swine flu shots?

As the first batches of swine flu vaccine arrive in the U.S., readers expressed concern about the safety of the new shots. NBC's Robert Bazell answers your questions.

As the first shipments of swine flu vaccine arrive in the U.S., readers expressed concern about the safety of the new shots and whether pregnant women should be vaccinated against the H1N1 virus. Others wondered about allergic reactions to the vaccine and if the swine flu and regular flu shots could be given together.

NBC's chief science and health correspondent Robert Bazell answers your questions about the  swine flu vaccine.

Should there be concern because this vaccine was rushed that there may not have been as extensive testing as other vaccines?  I would hate to encourage our employees to rush out and get the vaccine, only to find out there are issues discovered to cause more concern.
Sheila Kovach, Mentor, Ohio

The testing on this vaccine was faster, but no less thorough than testing on other vaccines. It went through the same set of procedures. It was done in a hurry, but health officials said they didn’t cut any corners. There is no reason to believe that the H1N1 vaccine is any more dangerous than seasonal vaccine, which is given to about 100 million people each year.

There is initial testing of safety and efficacy that’s done in a few hundred people. By necessity you can’t do it in thousands and thousands of people. So far, the vaccine seems to be safe in those people. To see a rare side effect, if there is one, you’d have to immunize hundreds of thousands of people.

On the off chance that there could be a rare side effect, there are huge monitoring systems in place. They'll detect any side effects pretty quickly, especially in the military, where service members are required to get the vaccine. Since the health of the military members is followed very closely, if something were to happen, we’d see it there first. In addition, electronic medical records kept by big hospitals and health insurance groups are being monitored for any evidence of side effects.

The government is making a big effort to point out that a certain number of things happen every day to people — miscarriages, heart attacks, seizures — and just because somebody gets one of these things right after they get a flu shot does not necessarily mean it’s a result of the flu shot. We’d have to make sure it is a pattern and not a coincidence.

If there is a common side effect, we’ll see it quickly. But it depends on how rare it is. If it’s 1 in 100,000, you'll need to do several hundred thousand vaccines before you’ll see it.

My daughter is 4 months pregnant. Should she get the swine flu vaccine?

Government health officials advise all pregnant women very strongly to get both the swine flu vaccine and seasonal flu vaccine. Approximately 1.2 million women give birth in the U.S. every year. Since the end of April, when swine flu first appeared, to the end of August, 100 women have been hospitalized and 28 have died, according to the Centers for Disease Control and Prevention. That’s not a lot compared to the number of women who are pregnant, and who are pregnant and who get influenza.

However, repeated studies have shown there are six times as many swine flu deaths and hospitalizations among pregnant women with swine flu as there are in the general population. It definitely is a risk factor. There are changes in a woman's immune system when she becomes pregnant that make her more susceptible. And in later stages of pregnancy, the baby pushes up on her lungs and makes it harder for her to breathe. That can make an influenza infection worse.

There are no indications the vaccine causes any side effect to either the mother or the unborn child. Health officials are monitoring that closely.

Why bother when the whole U.S. is pretty much widespread with swine flu already? How do we know the flu shot and the swine flu shot can be taken at the same time and there wouldn't be any side effects? Should we (adults and kids) be getting a pneumonia shot because they are linking this with H1N1?
Erica Beaver, Sugar Hill, Ga.

Swine flu is pretty much widespread in the U.S., but that hardly means that everyone in the U.S. who is going to get it has gotten it. We keep talking about it being a mild or moderate disease, but the people who have had it and come out fine talk about spending several days to a week being utterly miserable, sometimes more miserable than they’ve ever felt in their lives. You don’t want to get the flu if you don’t have to because it’s mighty unpleasant. You miss work and run the risk of infecting your co-workers. It’s a good idea to get vaccinated even though there have been a lot of cases out there already. It’s nowhere near run its course.

No one knows what’s going to happen because the flu is completely unpredictable. Yes, there have been a lot of cases, but there will be many, many more.

The swine flu and regular flu shot can be taken together, although the CDC recommends that, ideally, they be given separately. A lot of people would like to get them together just for convenience. The best course is to talk to your doctor about it. The vaccines are made in the same way and are very similar. It’s just because swine flu appeared so late in the year that it’s not part of the normal vaccination. So it’s a separate shot.

But if you can get it done all at once that’s fine.

Regarding the pneumonia vaccine, in very rare cases, swine flu infections can go deep into the lungs and cause a pneumonia that can be very quick and fatal.  An analysis of some of the deaths has shown that these infections are most often pneumococcal. It can also make someone susceptible to a bacterial pneumonia, which also can be fatal. There are two separate things that can co-exist. But the numbers are very small.

There is one kind of pneumococcal vaccine that is already recommended as a routine childhood vaccination. Children should be getting that just as they are getting measles, mumps and all the other childhood vaccinations. It’s important to make sure your child has had that.

For people who are at risk of complications, there is a  vaccine that protects against more strains. That is recommended for people at high risk.

What age is at most risk for the swine flu? I am most concerned for my adult children and grandchildren.
Lee Davis, Joliet, Ill.

The swine flu has been unusual in that it has affected mostly younger people. That’s one of the things that’s unusual about it.

Nobody is quite sure why that is, although they think it’s because older people have immunity to viruses that have circulated prior to the mid-1950s. But it’s a continuum — you can’t say if you’re a certain age, you’re protected. It probably doesn’t kill as many people because a lot of the people who die from each year from seasonal influenza are very sick and very old and the flu pushes them over the edge.

The number of people who are dying from swine flu is very low compared to the people who are infected. But it tends to be more of a tragedy when it’s a 14-year-old or an 8-year-old, than it is when you lose a very sick 90-year-old.

Millions of people have been infected with swine flu in the U.S. Only about 60 children under age 18 have died and a few hundred adults have died. It’s like getting struck by lightning. For some people, a very few number of people, there’s just no way to predict it. That’s why you want to get vaccinations out there — it’s not just to keep people from getting sick with the flu. It’s also to protect those people who — for whatever reason, sometimes it’s underlying conditions, sometimes it’s just chance — are very vulnerable.

I am allergic to eggs.  Will I be able to take the swine flu vaccine?

No. You will not be able to get the swine flu vaccine or seasonal flu vaccine because all of it is manufactured in eggs. If people have genuine severe allergies and have some kind underlying health condition that makes them think they really need the vaccine, they should check with their doctors. At the very least, if someone is susceptible, they should make an effort to be sure the people around them get the vaccine. And they should take seriously the advice about hand washing and covering coughs.

I have a 7-month-old baby and am concerned about the side effects of the new swine flu shot, however, I am also worried about my child GETTING the swine flu. I would prefer to get the vaccination for my husband, myself, and my son's grandmothers who care for him. I feel that would greatly reduce my son's risk of getting the swine flu without putting him at risk of side effects from the vaccine. Is this a good idea and how likely will it be that my husband and I and our mothers will be able to get the shot? Thank you.

It is a good idea and it is strongly recommended that people who care for children or come in contact with children age 2 and younger get the vaccines, both seasonal and swine flu. Every year, a handful of children with seasonal flu die suddenly and unexpectedly from influenza. There’s no reason to think it’s different from swine flu. There have been deaths in babies. But babies cannot be given the shot because their immune systems aren’t ready to be vaccinated against influenza.

The recommendation is that everyone who is around children 2 and under get vaccinated and take the normal hand-washing precautions.