Immunization quiz: The truth behind lifesaving vaccines

Shortages of a vaccine in any given year can lead to the impression that the overall vaccine supply isn't stable. For instance, the flu vaccine shortage during the 2004-2005 flu season overshadowed the fact that other vaccines were in adequate supply. Likewise, if you tried to get some routine vaccinations for your child a few years back, you were one of the frustrated parents told to wait because the vaccine wasn't available.

Public health officials are working to ensure that the overall vaccine supply remains sufficient. In the meantime, if you or your child is unable to receive a vaccine, talk with your doctor about being notified as soon as vaccine is available and about other precautions you can take to prevent disease, such as frequent hand washing.

If your child gets behind schedule in a vaccination series, there's typically no need to start over. In most cases, you can catch up with missed shots in one visit to the doctor's office. Any immunizations your child has already received usually still count toward the recommended schedule.

The influenza vaccine is offered every year because influenza viruses can mutate from year to year. And because the influenza viruses in circulation change from year to year, the vaccine you received last year may not be effective against the flu strains prevalent this year. Also, your immunity to influenza fades over the course of the year, so getting vaccinated every year offers you the best protection.

In recent years, some news reports have raised concerns about a connection between autism and vaccines. These reports have primarily targeted the measles-mumps-rubella vaccine (MMR) and any vaccines containing thimerosal, a preservative that contains a very small amount of mercury. However, groups of experts from the American Academy of Pediatrics, the Institute of Medicine and the Centers for Disease Control and Prevention have concluded that no scientifically proven link exists between these vaccines and autism.

The vaccine against Haemophilus influenzae type b (Hib) previously couldn't be used for infants. Yet infants were those most at risk of contracting — and possibly dying of — a Hib infection. With the development of this new vaccine for children, the incidence of meningitis caused by Hib was reduced from an estimated 20,000 cases a year in the early 1980s to an estimated 341 cases in 2000.

Some vaccines use a killed form of the virus or bacterium, and some vaccines use a live but weakened (attenuated) form of the virus or bacterium. Some vaccines use neither. They may use a sugar or protein molecule derived from or resembling one from the virus or bacterium. In each of these cases, the vaccine works by provoking a protective response from your immune system.

For instance, the flu shot — one of the methods for influenza vaccination — uses a killed (inactivated) form of the virus to stimulate your immune system into fighting that year's anticipated flu strains. The nasal spray for influenza vaccination contains live virus.

A small minority of people don't respond adequately to vaccines and may be susceptible to the disease even if they're vaccinated. Others may not be able to receive a certain vaccine if they're allergic to any vaccine components. These people are best protected from disease when all others around them are vaccinated, preventing the spread of disease to them.

One myth that seems to perpetuate itself is that the diphtheria, tetanus and acellular pertussis (DTaP) vaccine causes sudden infant death syndrome (SIDS). It doesn't.

SIDS strikes most often in babies between 2 months and 4 months of age. By the time he or she is 4 months old, the average American infant has received two doses of the DTaP vaccine. Because these two circumstances so coincide, some have incorrectly attributed the DTaP vaccine as a possible cause of SIDS.

In fact, as reported by the Institute of Medicine (IOM) in 2003, children who receive the DTaP vaccine aren't any more likely to die of SIDS than are children who aren't vaccinated. The IOM further revealed that some studies even show a decreased risk of SIDS for those children who are vaccinated.

There's no evidence that suggests vaccines pose unnecessary risk or side effects. The benefits of vaccines greatly outweigh any risks. People who aren't vaccinated face a greater threat from disease than from vaccination. Many more illnesses or deaths would occur were it not for vaccines.

One example is whooping cough (pertussis). Pertussis is a serious illness, causing severe coughing and difficulty breathing. It can lead to brain damage, seizures, mental retardation and death. Vaccination has been successful in reducing the number of pertussis cases reported each year in the United States by 99 percent. But if pertussis immunizations were stopped, a resurgence of the disease would surely occur — as evidenced by a falloff in vaccination rates in the United Kingdom and Japan in the 1970s and subsequent pertussis epidemics in those countries.

For reasons that aren't clear, the number of pertussis cases each year in the United States is now on the rise. Do what you can to protect your child from this disease. Get the recommended vaccine beginning at 2 months of age and adhere to the schedule for getting the remaining doses of vaccine.

All states require that children have vaccinations before entering school. Vaccinations not only help keep individual children healthy, but also curb epidemics of preventable diseases. However, many states offer exemptions for children whose parents disagree with immunizing for religious or philosophical reasons. Check with your state health department for more information.