By Daniel J. DeNoon
WebMD Health News
Sept. 13, 2010 -- As the 2010-2011 flu season approaches, it's once again time for flu vaccination. This year, the CDC advises just about everyone to get the vaccine. That raises questions. So does the inclusion of the H1N1 pandemic swine flu vaccine in the seasonal vaccine. To answer the questions, WebMD spoke with flu expert William Atkinson, MD, MPH, of the CDC's National Center for Immunization and Respiratory Diseases. Everybody can benefit from the flu vaccine. Up until 2009, it was recommended every year for everyone except for a small group of 18- to 49-year-old, non- pregnant people in good health. We just added that group. Everyone who does not want to get the flu can benefit -- and it certainly can save some people's lives. That's a very good question. The problem is that we have seen some severe illnesses and deaths in young, relatively healthy people. Some were adults under age 50 who weren't aware they had risk factors for severe flu illness. It is true that most flu deaths and severe illnesses occur in the extremes of age, in infants and in the elderly. But it does kill people who are healthy. And some people who think they are healthy have medical risks they are unaware of. Even someone with no underlying medical condition can get a very nasty flu illness, with missed days of work and a trip to the doctor's office. Why would anyone want that? In addition, vaccination of healthy people reduces their chance of becoming infected with the flu virus -- and passing the virus to someone at higher risk of complications, such as a baby or an elderly person. Probably one of the most common concerns we hear is from people who, right after getting a flu shot, got something that seems to them like flu. It is possible it could happen. After a dose of flu vaccine, it takes at least a week to become immune. If flu is in your community and you are exposed, it takes two or three days for symptoms to appear. So it is possible if you are exposed to flu to get sick before the vaccine has a chance to work. It gives people the impression the vaccine caused the flu. And the way people use it, "flu" is not a specific term. People have different ideas of what flu is. Other kinds of viral infections can cause a flu-like illness, but it is not flu. And influenza vaccine will not protect against that.
Keep in mind that the flu shot cannot produce a flu infection. It is dead -- it's just protein, with nothing live in it. So a lot of this is just coincidence -- either the vaccine did not have time to work, or you got something like the flu. But this is a very common perception, linking your flu shot to getting the flu. Even some doctors and nurses have this perception. The way our brains work is to have two things happen in sequence, and to conclude that the two things are connected by cause and effect. Vaccination is memorable, and the illness is memorable, and it is human nature to think one caused the other. But it is a perceptual problem rather than reality. FluMist is a really good option for people who are healthy and under 50 and not pregnant. It is live, but it has been modified so it only grows in a person's nose or throat. It does not get down into the lung. It is modified so it does not cause lung infection. This means the virus in FluMist does not cause flu the way we think of it as a respiratory infection. It can cause a sore throat for a day or two, but not flu with cough or fever. It really does not do that. The problem is the flu virus: It changes all the time. This means we have to change the vaccine all the time to keep up. Last year's vaccine is not like this year's vaccine. There are three different viruses that can cause flu. Vaccines that protect against each one are included in the 3-in-1 seasonal flu vaccine. One or more of these components is changed every year because the virus we are trying to prevent has changed. Unfortunately, being immune to one of last year's viruses may not protect you against this year's virus. It is a constant job of catch-up. And there probably is some waning of immunity over time, too, particularly with the shots. Researchers are looking for a way to make a vaccine that is not so sensitive to change in the virus. We are looking for a one-shot vaccine that will protect for years after a single dose. That is what we would all like, a flu vaccine you could get every five or 10 years. But that vaccine has yet to be invented. Yes. If you really had the flu during the pandemic, you probably are immune to the H1N1 swine flu. But there are other infections that can mimic influenza, and it could be some other virus that made you sick. Not all infections that act like flu are necessarily flu. Probably millions of people were infected with the 2009 H1N1 flu strain. But we can't tell which person had swine flu and which had something like flu -- unless they really had a viral-culture test to prove they really had H1N1 virus. Even then, remember, there is protection against two other flu viruses in this season's vaccine. If you went through having the 2009 H1N1 "swine flu," you certainly don't want to get sick again. And there's a bonus for people who had an H1N1 infection last year: It will boost their immune response to the H1N1 component of the seasonal vaccine, and they will get additional immunity from the other two components of the vaccine. The CDC and the FDA did an enormous amount of monitoring of the 2009 H1N1 swine flu vaccine. After tens of millions of doses, we have no evidence that vaccine was any less safe than any of the vaccines we have used for years. Our monitoring showed the side effects of the H1N1 vaccine were pretty much the same as you'd see from regular seasonal vaccines. There was no indication the pandemic vaccine was any less safe than any vaccine we've ever produced. So including that vaccine as one of the three in this year's seasonal vaccine will not change the safety pattern. Even so, we will monitor the safety of this year's seasonal vaccine closely-- as we always do. It's really quite complicated for parents whose children are 8 years old or younger and who have never been fully vaccinated against the flu. How many doses of flu vaccine will a child under age 9 years need this year? It will depend on two things: