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The following are two excerpts from Vaccines and Your Child: Separating Fact from Fiction:
Are vaccines given on a one-size-fits-all schedule?
Some parents wonder how the same vaccine can be recommended for a 10-pound baby as for a 200-pound adult. Wouldn’t it make more sense to give a baby a smaller amount of vaccine? That’s exactly what is done for drugs, where the amount prescribed is often determined by weight or age.
Indeed, some vaccine dosages given to children and adults aren’t the same. For example, the influenza and hepatitis B vaccines given to children contain lower quantities of vaccine than those given to adults. Sometimes the opposite is true. For example, the amount of diphtheria and pertussis vaccine contained in the DTaP vaccine given to children is actually more than is in the Tdap vaccine given to adolescents and adults (see the section on Diphtheria, Tetanus, and Pertussis). That’s because adolescents and adults often have more serious local reactions to the diphtheria and pertussis components of the vaccine than young children.
But the need to take into account weight when determining dose isn’t the same for vaccines as it is for drugs. Drugs enter the bloodstream and are distributed throughout the body. That’s not true for vaccines. Vaccines are typically injected into the arm, leg or buttocks. The vaccine then travels to nearby lymph nodes, which are collections of immune cells located throughout the body. Once in the lymph node, the vaccine enters a type of immune cell called an antigen-presenting cell. These cells present the vaccine to other cells of the immune system responsible for making antibodies (see "How do vaccines work?").
As a general rule, vaccines stimulate the immune response in the area where the vaccine is given, not throughout the body. Adjuvants, which are substances occasionally added to vaccines to enhance the immune response, also act only locally (see "Do vaccines contain harmful adjuvants like aluminum?"). All of this means that, for the most part, how much someone weighs doesn’t matter, because vaccines aren’t distributed throughout the body.
The next logical question would be, how are children protected against infections that enter in different places, like the nose, throat, or intestines? The answer is that although immune cells, like those that make antibodies, are typically generated where the vaccine is given, they travel throughout the body, offering protection at the many sites where infections might occur.
When vaccines are tested, children are put in groups given different doses to determine which works the best; these are called dose-ranging studies. The goal is to give the minimal amount of vaccine that is capable of inducing a protective immune response, so that the vaccine is least likely to cause side effects.
Is there any harm in using an alternative schedule?
During the first few years of life, children can receive as many as twenty-six separate inoculations and five shots at one time. For most parents, it’s hard to watch children restrained against their will and injected again and again with so many shots. So it’s easy to appeal to the sentiment that it might be of value to create an alternative schedule that separates, delays, withholds, or spaces out doses of vaccines.
The perceived value of an alternative schedule is that it might avoid weakening, overwhelming, or altering the immune system of the young child. However, abundant evidence shows that this is not the case (see the chapter titled "Safety"). Another argument for spacing out vaccines is that they contain potentially harmful additives that might be toxic if too many are given at once, but again, evidence does not support this fear (see the section titled "Ingredients"). Yet another argument is that too many vaccines are causing specific diseases like asthma, allergies, autism, diabetes, and multiple sclerosis—diseases that could be avoided by choosing a different schedule. But again, no evidence supports these contentions (see "Safety"). Some parents (as well as some doctors) argue that even if it’s true that children’s immune systems can easily handle the challenge of vaccines, there’s no harm in spacing them out. This isn’t true for several reasons.
Increased Duration of Susceptibility to Disease
The biggest problem with an alternative schedule is that it increases the time during which children are susceptible to vaccine-preventable diseases. If immunization rates across the United States were about 95 percent, this wouldn’t be a problem. Parents could hide their children within a highly protected population knowing they wouldn’t be hurt by bacteria and viruses. But that’s not the case. Population (or herd) immunity—the ability of a vaccinated community to protect those who can’t or won’t be vaccinated—has broken down. As a consequence, outbreaks of pertussis (or whooping cough) are common; a measles epidemic in 2008 was larger than any measles outbreak in more than a decade; and children are starting to die from bacterial meningitis because their parents are choosing to either delay or withhold vaccines. (For example, outbreaks of Hib meningitis caused the deaths of four unvaccinated children in Minnesota and Pennsylvania in 2008 and 2009.) Parents who make the choice to delay vaccines are taking an unnecessary risk without deriving any benefit.
No Data to Support Safety and Effectiveness of an Alternative Schedule
Another problem with the alternative vaccine schedule is that it’s untested. Every time a new vaccine is added to the recommended schedule it’s tested to make sure that it doesn’t interfere with the immune response or safety of the existing vaccines and vice versa (see "How do we know that different vaccines can be given at the same time?"). Making up a schedule that is untested takes an unnecessary risk, again without benefit.
Another reasonable argument for spacing out vaccines is that it would mean fewer shots at one time, and therefore less pain for the child. Interestingly, researchers have found that children experience similar amounts of stress—as measured by secretion of a hormone called cortisol—whether they are getting one or two shots at the same visit. This suggests that although children are clearly stressed by receiving a shot, two shots aren’t more stressful than one. For this reason, more visits to the doctor created by separating or spacing out vaccines will likely only increase the trauma of getting shots.
Offit, P. A. and C. A. Moser. "The Problem with Dr. Bob’s Alternative Vaccine Schedule." Pediatrics 123 (2009): e164–e169
Ramsay, D. S. and M. Lewis. "Developmental Changes in Infant Cortisol and Behavioral Response to Inoculation." Child Development 65 (1994): 1491–1502.
Are vaccines safe?
A vaccine is safe if its benefits clearly and definitively outweigh its risks. But any medical product that has a positive effect—whether it is a drug or a vaccine—can have a negative effect. So no vaccine is absolutely safe. All vaccines that are given as shots can cause pain, redness, or tenderness at the site of injection. And some vaccines cause more serious problems. For example, the measles vaccine can cause a decrease in platelets, which help the blood to clot. This happens in about 1 of 25,000 children who get the vaccine. This particular reaction, called thrombocytopenia, shouldn’t be surprising since natural measles infection can do exactly the same thing, except much more commonly and much more severely.
Other vaccine side effects can be quite severe. Influenza vaccine is grown in eggs, and some people, about one half of one percent (or about 1 in 200), are allergic to egg proteins. These people can have a severe allergic reaction to influenza vaccine that includes symptoms such as hives, difficulty breathing, low blood pressure, and even shock. That’s why doctors often ask patients to stick around for about fifteen minutes after they get vaccines—because this type of severe allergic reaction, although quite rare, happens very quickly.
Influenza vaccine isn’t the only vaccine that can cause a severe allergic reaction. The chickenpox vaccine contains gelatin as a stabilizer. Some people are severely allergic to gelatin and develop severe allergic symptoms in response to the chickenpox vaccine.
But while there are small risks to vaccines, nothing is risk-free. Probably the most dangerous aspect of vaccines is driving to the doctor’s office to get them. Every year about 30,000 people die in car accidents. Walking outside on a rainy day isn’t entirely safe; every year in the United States about 100 people are killed when they are struck by lightning. And hundreds of people die every year when they slip and fall in the bath or shower. So even routine daily activities pose a certain degree of risk. We choose to do them because we consider the benefits to outweigh the risks.
In the chapters that follow we will describe in detail the benefits and risks of every vaccine. ’And you’ll see that for children who don’t have a preexisting medical condition that would preclude getting a vaccine, the benefits of every vaccine outweigh its risks.
How do I know if a problem is caused by vaccines?
Because we are all human, we naturally look for reasons something happened. The process of seeking to understand what causes various problems has been crucial to our success as a species. And sometimes bad things happen to young children. They suffer asthma, allergies, autism, developmental delays, hyperactivity, or attention deficits, among other health problems. Worse: sometimes they die of poorly defined disorders like Sudden Infant Death Syndrome (SIDS). Some of these problems might occur soon or immediately after receiving them.
So how can you know whether symptoms that follow a vaccination were caused by the vaccine? The best way is by performing controlled studies. ’For example, in 1998, British investigators proposed that the combination measles-mumps-rubella vaccine (MMR) might cause autism. At the time, about 1 in 2,000 children in England were diagnosed with autism and about 9 of 10 were given the MMR vaccine. To determine whether MMR caused autism, researchers studied hundreds of thousands of children who did or didn’t receive the vaccine (see "Do vaccines cause autism?"). If the vaccine caused autism, then the number of children with autism should be greater in the group that received the vaccine than in the group that didn’t receive it. But it wasn’t. In fact, the incidence of autism in children who got MMR was the same as in those who didn’t get it.
However, when trying to determine whether a vaccine causes a particular problem, one study isn’t enough; other investigators should repeat it to make sure that the results hold up across different populations of children. That was done with investigations into the MMR-causes-autism theory. Twelve studies performed by different groups of investigators working on several different continents all showed the same thing: MMR didn’t cause autism. Although no epidemiological study is perfect, they can be quite powerful, capable of determining whether a vaccine caused a problem in as few as one in a million vaccinated children.
Many parents who read about the investigations of MMR were reassured by the results, but some weren’t. They had been compelled by what they had seen, and no study could convince them otherwise.
One Person’s Story
Anecdotal experiences can be very powerful. For example, a professor emeritus at Duke University School of Medicine tells the story about a friend’s four-month-old child who was taken to a clinic to get a diphtheria, tetanus, and pertussis (DTP) vaccine. The father waited and waited in line. Finally, he tired and took the baby home without getting the vaccine. At home the father put the child to bed. Several hours later, the child was found dead in his crib, the victim of Sudden Infant Death Syndrome (SIDS). Had the father actually given his child the vaccine, no amount of statistical evidence in the world would likely have convinced him that anything other than the vaccine was the cause.
Myers, M. and D. Pineda. Do Vaccines Cause That?: A Guide for Evaluating Vaccine Safety Concerns. Galveston, TX: Immunizations for Public Health, 2008.
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