How Vaccines Work
Most people wonder how a needle filled with fluid keeps their child safe from disease.
The goal of a vaccine is to make a person immune to a germ.
The immune system helps to protect the body against infection by identifying germs such as bacteria and viruses and removing them from the body.
A vaccine is a substance (a weakened or dead form of the disease) that stimulates the immune system to make antibodies and memory cells, which are the body’s main defenses against infection, without the risk of illness or death.
Once the immune system has found a germ that should not be in the body it creates antibodies and memory cells. The antibodies help get rid of the germs. The memory cells can live for a very long time, sometimes forever. Memory cells let the immune system recognize germs it has seen before so if the germ ever enters the body again it can be destroyed before causing any harm.
Not all memory cells can live forever. This is why we need to have booster shots. Booster shots remind the immune system how to fight against the germs.
(Adapted from “Your Child’s Best Shot: A Parent’s Guide to Vaccination” 3rd Edition)
Vaccine Safety
Most parents today have not had any direct experience with many of the infections vaccines protect us against so they may not know about the serious and sometimes fatal outcomes of the diseases. As a result, parents worry more about the side effects of vaccines then the diseases they prevent.
Vaccines are one of the safest tools utilized in modern medicine and serious side effects are very rare. Canada has many systems in place to make sure the vaccines we give our children are safe. Before any vaccine is approved for use in Canada, it must be shown to be safe and effective in preventing the disease that it targets.
Health Canada takes vaccine testing very seriously. The Biologics and Genetic Therapies Directorate (BGTD), regulates vaccines used in humans in Canada. Vaccines MUST meet the BGTD’s standards for production, safety and strength before they are released for use.
Vaccine monitoring systems are also in place in Canada to monitor severe side effects related to vaccines, review information on specific vaccines and make recommendations on any action that should be taken. The Immunization Monitoring Program ACTive (IMPACT) and the Canadian Paediatric Society Program (CPSP) monitor adverse vaccine events in Canada.
All vaccines are also reviewed by the National Advisory Committee on Immunization (NACI) who makes the final recommendations.
(Adapted from “Your Child’s Best Shot: A Parent’s Guide to Vaccination”, 3rd Edition)
Vaccine Effectiveness
Most people often ask the question, “Do vaccines really work?” The answer is YES!
Although no vaccine is 100% effective, all of the vaccines used for routine immunization of children and adults are very effective in preventing disease. In fact, the vaccines are so effective that most of the diseases they protect against are now very rare.
The statistics below clearly show a drop in disease rate after the introduction of vaccines.
|
DISEASE |
BEFORE VACCINE |
AFTER VACCINE |
Polio |
Epidemic years had up to 20000 cases of paralytic polio. |
Disease has been eradicated in North America, but is still prevalent in other parts of the world. |
Diphtheria |
Highest in 1924 with 9000 cases. |
Today, 205 cases reported each year. |
Tetanus |
Average of 40 to 50 deaths per year. |
3 to 5 cases reported per year. No deaths since 1991. |
Pertussis |
Average of 153 cases per 100000 people each year. |
Average 10 cases per 100000 people each year. |
Haemophilus B (Hib) |
Leading cause of bacterial meningitis in infants. About 2000 cases per year. |
Less than 60 cases per year over the past few years. |
Measles |
About 300000 to 400000 cases each year. |
Less than 400 cases per year since the 2-dose schedule introduced. |
Mumps |
Highest in 1942 with 52344 cases. Average of 136 cases per 100000 people each year. |
Average of 2.35 cases per 100000 people each year. |
Rubella (German Measles) |
Highest in 1939 with 69401 cases. Average of 149 cases per 100000 people each year. |
Average of about 8.5 cases per 100000 people each year. |
(Adapted from the Canadian Immunization Guide 6th Edition)
Since we no longer see the effects of the above diseases, some people think we no longer need vaccinations. The truth is we still need vaccines to keep diseases under control.
For example:
- In 2000, Ireland saw more than 1200 cases of Measles, compared with only 148 in the year before due to a drop in immunization rates.
- In 1994, Russia had 5000 deaths due to diphtheria after their organized immunization program was stopped. In previous years Russia (like Canada) had only a few cases of diphtheria each year and no deaths.
- In 1999, a large outbreak of Rubella (German measles) occurred in Nebraska. All 83 cases in this outbreak were adults who had not been immunized.
Vaccine Myths, Facts and FAQ's
MYTH:
Vaccinations are no longer necessary as the diseases that we vaccinate for have already disappeared.
FACT:
- Some diseases remain so common that without the vaccine the disease is almost guaranteed to occur (e.g. Chickenpox).
- Some diseases may not be common but still exist in our country (e.g. Measles, Mumps and Pertussis). Vaccines can protect us and protect those around us from spreading these illnesses.
- Some diseases that do not exist in our country are common in other countries (e.g. Polio, Diphtheria). Because world travel is now so common, travellers or immigrants may bring disease into the country.
- Some diseases are caused by bacteria that live in the environment (Tetanus). The only way to protect yourself is by vaccination.
MYTH:
Vaccines are bad for my body and too many vaccines may harm my immune system.
FACT:
- Vaccines strengthen the immune system and protect us from some serious diseases.
- Vaccines are not strong enough to overload the immune systems memory.
- Scientists believe the body can recognize and respond to about 10,000 different organisms at one time.
- Everyday we are exposed to many types of germs while eating, drinking, playing, and working.
MYTH:
I am too old to be vaccinated. Vaccines are only for children.
FACT:
- Some vaccines require the use of a booster to increase the protection that the vaccine provides.
- Getting a booster dose ensures that our immune system is at it’s best fighting ability to protect our bodies from illness and disease.
- No matter what your age, vaccinations such as Tetanus and Diphtheria should be kept up to date for best protection.
- Some vaccinations are just as important for older people as they are for younger people such as Pneumococcal and Influenza.
You are NEVER too old to be vaccinated.
MYTH:
If I live a healthy lifestyle I won’t need to receive vaccines to be protected from diseases.
FACT:
- A healthy lifestyle is always a good choice. Staying healthy will increase the body’s ability to fight infection.
- Most illnesses can still make you very sick even if you are very healthy.
- Vaccinations strengthen your immune system by safely introducing a weakened or dead form of the disease into the body. The only other way for the body to recognize the disease is if the body is exposed to natural infection which then can cause illness or even death.
MYTH:
Vaccines can cause autism and seizures.
FACT:
- There is no link between autism and vaccinations. Autism usually shows up in the first 18 months of life and this is also a time period when many vaccines are given. Many studies have been completed and no link has been found between vaccines and autism.
- Vaccines can cause fevers in some children that may lead to seizures. These are called ‘Febrile Seizures’ and usually occur in children whose parents or siblings have experienced them. A fever from any source can trigger a febrile seizure in about 3% of children. The number of children who experience febrile seizures after vaccination is very low. Febrile seizures do not cause brain damage.
(Adapted from Simcoe Muskoka District Health Unit)
Last reviewed: February 28, 2011