KIDS
May 15, 2009

Vaccines, What to Know

Always check with your child's physician before delaying an immunization.
Vaccination is one of our biggest health success stories. Vaccines are a major reason for the improvement of personal, societal, and world health. As a result of vaccination programs, smallpox was eradicated in 1977 and polio was eradicated from the Americas in 1991. There has been a significant decline in the incidence of vaccine preventable diseases such as diphtheria, tetanus, pertussis (whooping cough), and children today are protected against many illnesses that their parents experienced. Despite these impressive benefits, parents are often concerned about the discomfort to their children and the possibility of serious side effects.

It's easy to lose sight of the need for compliance with vaccines since their success has prevented the public from personally experiencing the devastating effects of certain illnesses.

How Vaccines Work
A vaccine contains a small or modified piece of the organism that causes a disease. It is similar enough to the real organism that the body's immune system reacts by producing protective antibodies against it. It is different enough from the real organism that the vaccine recipient gets only a mild reaction rather than the actual illness. In order for vaccines to work, the body's immune system must be mature enough to recognize an invader and make antibodies against it.

Since the younger the child, the sicker they become if they catch an illness, one of the challenges in immunization science has been developing vaccines which would be capable of stimulating immune responses in very young children. There are currently vaccines that prevent children under the age of 2 years from getting 14 diseases This has resulted in a very full schedule of immunizations from infancy through toddlerhood, as many vaccines require two or more doses to produce a protective level of antibodies to fight off disease. Efforts have been made to reduce the number of needle sticks by producing combination vaccines which contain serum against more than one disease without decreasing the effectiveness of the individual components or increasing the risk of side effects.

It's easy to lose sight of the need for compliance with vaccines since their success has prevented the public from personally experiencing the devastating effects of certain illnesses. But a look at pre- and post- vaccine history and a look at the illnesses current vaccines protect against provide compelling evidence for the ongoing impact of immunizations. For example, between 1958 and 1962, five years before the MMR (measles, mumps and rubella) vaccine was licensed, there were 503,282 cases of measles in the United States. In 2004, the number of cases had dropped to 258, a greater than 99% decrease.

What Diseases Can Vaccines Prevent?
What follows are a few examples of diseases that are currently preventable with immunizations. See Table 1 for a complete vaccination schedule.

Hepatitis B : Hepatitis B virus (HBV) is transmitted from one person to another through blood and body fluids, and primarily infects the liver. In the United States, it is most commonly spread through sexual contact or injection drug use. Worldwide, it is most commonly spread to infants by their infected mothers. More than half of people who are infected do not show signs of the disease. Each year, approximately 4,000 to 5,000 children are infected with HBV in the United States. The younger the person is when they catch the hepatitis, the more likely it is that he or she will develop chronic liver disease or liver cancer. Approximately 90% of infants, who are infected from their mothers at birth, and between 30 and 50% of those infected before age five, become chronic HBV carriers. This is why hepatitis B immunizations are recommended routinely starting at birth.

Hepatitis A : This infection is caused by the hepatitis A virus (HAV), which is most commonly spread in stool, although it can be spread through contact with infected blood. Infection is transmitted from person to person in households and extended family settings. Adolescents and adults are more likely than young children to develop signs and symptoms of disease. It usually lasts less than two months. However, 10% to 15% of those infected will have prolonged or relapsing disease lasting as long as six months. Fortunately, unlike hepatitis B, chronic hepatitis A disease does not occur. Each year in the U.S., 125,000 to 200,000 people become sick with hepatitis A. Since most infected pre-school children show no symptoms of hepatitis A infection, they often unknowingly spread the hepatitis A virus to others. Prior to the introduction of hepatitis A vaccine, about one-third of the hepatitis A cases in the U.S. occurred in children 5 to 14 years of age.

Haemophilus influenzae type b (H. flu) : This is a bacterium that can infect the lining of the brain causing meningitis. It is transmitted from person to person by coughing or sneezing and invasive disease occurs most often at three months to three years of age, peaking at six to seven months. It is rare after age five years. H. flu can cause a wide variety of serious infections, including pneumonia, severe throat swelling that makes breathing difficult (epiglottitis), and infections of blood, bones, joints, and the covering of the heart. Complications of H. flu meningitis include blindness, deafness, mental retardation, learning disabilities, and death. About 5% of children (500 out of every 10,000) with H. flu meningitis die despite antibiotic treatment.

Streptococcus pneumoniae : These are a group of bacteria also known as pneumococci. They live in the nose and throats of people of all ages and can infect many places including the middle ear (otitis media), sinuses (sinusitis), lungs (pneumonia), the central nervous system (meningitis), and blood stream (bacteremia). Serious pneumococcal infections are most common in infants, toddlers, smokers, and the elderly.

Other early childhood vaccines protect against measles, mumps, German measles (rubella), chicken pox (varicella), and polio. As discussed below, most schools require these vaccines.

For Adolescents
In recent years there have been some developments in vaccines for adolescents.

Booster shots for pertussis are currently recommended for adolescents at age 11-12 years because the immunity from the early childhood vaccine wanes and adolescents and adults, who develop only mild symptoms from this germ, pass it on to young infants who develop serious respiratory disease.

A vaccine against the human papilloma virus , HPV, is now recommended for administration to girls before the onset of sexual activity. It protects against certain strains of HPV that have the potential to cause cervical cancer.

The meningococcal vaccine is now recommended for all adolescents and is particularly important for college freshmen who will be living in dorms. This potentially deadly disease is known to spread in crowded living areas such as dorms and military housing.

Table 1.
Vaccination Schedule for Children and Adolescents
Vaccine Age(s) Given
Hepatitis B Three doses completed by age 18 months
Rotavirus Three doses at 2,4,6, months
Diphtheria, tetanus, acellular pertussis Four primary doses completed by 18 months, booster at 4-6 years
Diphtheria, tetanus and acellular pertussis — booster with a smaller diphtheria component At 11-12 years or 13-18 years
Haemophilus influenzae type B Four doses completed by 18 months
Pneumococcal vaccine Four doses completed by 18 months
Inactivated polio virus Four doses complete by 18 months and booster at 4-6 years
Influenza Yearly starting at 6 months
Measles, mumps and rubella Two doses, first, 12-15 months, second, 4-6 years
Varicella Two doses first 12-15 months, second 4-6 years
Hepatitis A Two doses completed between 12-23 months
Meningococcal vaccine Given at 11-12 years or 13-18 years if not previously immunized
Human Papilloma Virus (HPV) Three dose series for girls at 11-12 years or 13-18 years if not previously immunized:

Concerns About Autism and Other Risks
Through the years there have been numerous controversies and concerns about side effects from vaccines and their components. Both parents and physicians have wondered whether they contribute to the onset of severe neurological diseases and autism. Unfortunately, many of the debilitating childhood neurological diseases begin during the first few years of life, which is also the time filled with vaccinations. Some of the diseases present subtly at first, and early clues are missed until major developmental milestones such as walking, talking and relating socially are delayed or lost. This has contributed to the confusion about whether or not the onset of symptoms of these serious diseases was related to the last immunization.

Thimerosal
Attention was focused on thimerosal, an organic compound containing mercury, that was widely used as a preservative in vaccines. It was necessary when vaccines were dispensed in multidose vials because the rubber seal was punctured by many needles for many patients, and each puncture had the potential to contaminate the vaccine serum with bacteria or fungi. Thimerosal effectively protected against the possibility of giving contaminated serum to children. However, in 1999, as concern for the potential toxicity of mercury compounds to the central nervous system grew, vaccine manufacturers were urged to reduce or eliminate thimerosal. A comprehensive review of thimerosal in 1999 found no evidence of its' playing a role in neurologic disease in young children and multiple other studies have repeated this finding.

Autism
The CDC also looked into the possibility of a link between thimerosal and autism. In 2004, the Immunization Safety Review Committee reviewed previous and new data from Denmark, Sweden, and the United Kingdom and concluded that there was no causal relationship between thimerosal containing vaccines and autism and other neurodevelopmental diseases. However at this time, all vaccines recommended for children 6 years of age and younger, except some brands of inactivated influenza vaccine, have trace or no amount of thimerosal. And vaccines are available in single dose vials.

...[T]he Institute of Medicine's Vaccine Safety Committee issued a statement that scientific evidence does not support a causal relationship between MMR vaccine and autism.

A second concern was raised about a possible causative relationship between autism and the MMR vaccine. Multiple studies have been done which have not yielded a positive correlation between MMR and the onset of autism. In 2000, the Institute of Medicine's Vaccine Safety Committee issued a statement that scientific evidence does not support a causal relationship between MMR vaccine and autism.

What Parents Need to Know
Vaccine safety is monitored in a variety of ways. Since the National Childhood Vaccine Injury Act of 1986, physicians and other health professionals are required to report adverse reactions to VAERS (Vaccine Adverse Event Reporting System). An active surveillance system, The Vaccine Safety Data Link obtains data on over 10 million children provided by contracts with large Health Organizations. The Clinical Immunization Safety Assessment Act (CISA) was established by the CDC in 2001 to advise clinicians on evaluation, diagnosis and management of adverse reactions following vaccines, and to conduct research on outcomes.

Keeping to the immunization schedule as closely as possible is important. Sometimes parents cancel shot appointments for the wrong reasons. If a child has a mild illness with a low-grade fever, or a diarrheal illness but is otherwise well, or has had an illness which is getting better, or is improving but still being treated with antibiotics, she can get her shot. If she had a reaction to a previous vaccine that caused soreness, redness or swelling around the vaccine site, or a temperature less than 105° F or if she was premature, she can get her shot. If someone in the child's household is pregnant, the child can get her shots. The pregnant family member can check with her obstetrician if she has concerns.

In fact, it is always important to check with your child's physician before delaying or skipping immunization appointments, since getting off schedule delays the time until your child is fully protected from diseases.

All states have guidelines for vaccine requirements for preschool and school entry. These can be obtained from the local health department or the Department of Education. Many colleges also have requirements that can be obtained from the individual college health offices.

There are many sources of information about vaccines on the web:

For Further Information
Descriptions of every vaccine preventable disease can be found at: http://www.immunizationinfo.org/vaccineInfo/vaccine_detail.cfv?id=5

Current information on vaccine safety surveillance by CISA is on their website: www.vaccinesafety.org

General information and information about state specific vaccine requirements can be found at the website of the National Network for Immunization Information: www.immunizationinfo.org

The Centers for Disease Control contains all the recommended vaccine schedules, information for travelers, and information about special considerations such as children with immunological diseases or other special cases: www.cdc.gov/nip

Vaccines have made a significant improvement in the lives of children and adults. It is important to maintain the standard of immunity by continuing to give our children their shots. For some diseases, such as smallpox, we may reach the ultimate goal of vaccination, which is to eliminate the disease entirely.
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