Is the swine flu shot as safe as regular vaccine?

Dr. Nancy Snyderman Chief medical editor

Even as millions of Americans clamor to a hard-to-find swine flu shot, many viewers and readers expressed worries about risks from the new vaccine. Others wondered how soon they would be immune to the virus after being vaccinated.

NBC's chief medical editor Dr. Nancy Snyderman answers your questions about H1N1.

Are there significantly different risks in getting a swine flu vaccination vs. the regular seasonal flu shot?
Mittendorf, Thomas, Metropolis, Ill.

The safety data from the clinical trials on the swine flu vaccine is extraordinarily strong. It's not a new vaccine. It's just a component that emerged too late to get it wrapped up. If H1N1 had popped earlier in the year, the manufacturers would have been able to incorporate it in the seasonal flu shot and we wouldn’t be having so much confusion.

When I was at a medical meeting recently, the moderator asked how many people had gotten a seasonal flu shot. Of about 500 doctors in the room, every hand went up. They were then asked, how many people are going to get H1N1? Every hand went up. The medical community understands that this is all about safety and protecting people.

We have a shot that can prevent illness and can prevent death. The shot is safe. There is no downside to this. The only group that should consider not getting it are people who have severe allergy to eggs because it is grown in eggs. For a very small population that’s the only caveat.

For them you have to hope that your neighbor is going to do the right thing [and get vaccinated], that the herd immunity will protect you.

If you have had H1N1 should you still get vaccinated?  What if you don't know if you've had it or not? They are asking us to stay home and are not testing all suspected flu cases in our area.
Jennie Arbogast, Dover, Ohio

Most doctors aren’t even checking for what type of flu you’re coming down with now because the assumption is that seasonal flu hasn’t come on the surface yet, that anything out there right now is H1N1. Most doctors are saying that if you have influenza, from spring through the summer to right now, you probably have had H1N1.

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If swabs are being done, it can come up as just Influenza A. It’s doesn’t really matter, frankly. Whether H1N1 is a subtype of Influenza A, or whether you’re infected with one or the other, it doesn’t matter. The treatment is still the same: take antivirals, stay home.

If you’re not sure whether you really had swine flu, then you might as well go ahead and get vaccinated. You can’t hurt yourself by getting vaccinated, even if you might have already had the flu.

I know there is thimerosal in the H1N1 vaccine. How concerned as parents do we need to be? Is it a small amount and what would be the long term or short-term side effects? Can you get vaccines without mercury preservative?
Audrey, Baldinelli, Inman, S.C.

There is no preservative in the nasal spray or in the single dose vaccine. There are minute amounts of ethyl mercury in the multiple dose vials to keep them sterile. There is no link between this preservative and autism, seizures, schizophrenia, mental illness or neurological problems. None. It has been proven over and over again to be safe.

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In a very perfect world none of us would have any mercury in our bodies, period. But the reality is, we do have small amounts of mercury in our bodies — from everything from volcanic eruptions to the fish we eat. However, the amount of ethyl mercury in a vaccine is so minute that it doesn’t even register.

If you can't get a single dose vaccine, then you have to decide whether not to be vaccinated, or to take the shot that comes from of the multiple dose.

I got my H1N1 because I’m a health care worker and I got it out of the multiple dose vial. It was either that or not get vaccinated. But the risk is so nonexistent. The chance of complication from the flu is far exceeds any complication from the vaccine — whether it’s preservative-free or has a preservative in it.

My 8-year-old just received her first dose of the swine flu vaccine, the shot form. Will this give her any immunity until 28 days when she can go for the second one?
Michele, Gilmore, Brick, N.J.

Yes, immunity starts in about 10 days. There is partial immunity, while the real antibody production starts in about 2 weeks. That’s why you want the booster three weeks later.

Is the H1N1 flu vaccine a live-virus vaccine or a killed-virus vaccine?   
Susan Fisher

INTERACTIVE Building a vaccine Preparing for the flu, every year

The nasal spray is an altered, live virus. It’s anttenuated. It’s perfectly safe, but it’s not given to children under the age of 2 or to pregnant women. The vaccine in the shot has been killed. It’s dead.

If you were around someone who later had a confirmed case of swine flu, could you be a carrier and spread it even if you don't have symptoms?
Jo Ann Kurtz, Howell, Mich.

People can be carriers of a virus and not come down with an infection. But that is more common in people who already have some level of immunity and not a youngster with no defenses against H1N1. 

That said, swine flu is not more contagious than seasonal flu. The reason we’re talking about it so much, this virus has jumped species, from pigs to human and that gets our attention.

It’s a novel virus, which means it’s never really been seen in our younger population before. It’s not particularly a killer, but it’s very, very efficient. It has attacked primarily young people because they have no immunologic memory for it. That’s why we’re talking about vaccination so much.

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