The Facts

Children are born with a natural immunity to certain infections. Antibodies pass through the mother's placenta to the fetus before birth, protecting the baby from infection. Breast-fed babies continue to receive antibodies from their mothers' breast milk. However, this natural immunity eventually wears off, usually within the first 6 months of life, and the protection is imperfect for many diseases.

In the past, a number of serious childhood diseases reached epidemic proportions, claiming thousands of lives and often leaving children with lasting mental or physical problems. Vaccines can now prevent many of these diseases. Vaccines work by introducing modified versions of viruses and bacteria into the body. They don't cause disease but the body still produces antibodies to fight it. These antibodies remain in the body to identify and fight the virus or bacteria in the future. Immunization often provides people with lifetime protection against once-common diseases.

Vaccinations for Particular Diseases

Vaccinations are available for a number of diseases, including:

  • chickenpox
  • diphtheria
  • Haemophilus influenzae type b
  • hepatitis B
  • measles
  • meningitis
  • mumps
  • pneumonia and other infections caused by the pneumococcus bacteria
  • polio
  • rubella
  • tetanus
  • whooping cough (pertussis)
  • diarrhea caused by rotavirus
  • influenza virus types A and B
  • human papillomavirus (HPV)
  • COVID-19

Many other vaccines exist for other, less common diseases. They are typically given to adults rather than children and are mostly related to travelling to less developed areas of the world.

Chickenpox is a very common childhood illness caused by a virus called varicella-zoster. It's highly contagious and is spread through the air or by physical contact with someone's open blisters. It rarely causes a serious illness, but a child with chickenpox can be sick for 7 to 10 days, and at least one adult will need to miss work to care for the child.

Diphtheria is caused by a strain of bacteria (Corynebacterium diphtheriae) that infects the throat, mouth, and nose. It's quite contagious. Sore throat, slight fever, and chills may be followed by a greyish membrane growing across the throat, making swallowing and breathing difficult. If the membrane covers the windpipe, air is blocked and a person is in danger of suffocating. If not treated fast enough, diphtheria causes a toxin that spreads and poisons the heart muscle and sometimes the nerves. This can result in short-term paralysis or heart failure. Diphtheria is fatal for about 10% of those who get it. Occasional cases of diphtheria are reported in Canada every year.

Hemophilus influenzae type b bacteria can cause serious illness, especially in young children under the age of 5 years. This infection commonly leads to pneumonia, as well as infections of the blood, joints, soft tissues, throat, and less commonly bones and the covering of the heart. This organism was once the most common cause of bacterial meningitis (inflammation of the lining of the brain and spinal cord). Children who get meningitis are at risk of death (3% to 6%) or permanent hearing impairment or brain damage (15% to 30% of survivors).

Hepatitis B virus is transmitted through exposure to contaminated blood (most commonly intravenous drug use) or through sexual contact, and can also pass from a mother to her baby during birth. It can cause inflammation of the liver (hepatitis), which can lead to destruction of normal liver tissue (cirrhosis), or liver cancer.

Hepatitis A virus causes liver inflammation and jaundice (yellow skin and eyes) and though most victims are ill for 10 days to 2 weeks, the infection rarely causes serious liver damage. It is spread primarily through ingestion of contaminated food or water.

Measles, mumps, and rubella are all caused by viruses and are highly contagious.

  • Measles lasts for 1 to 2 weeks, causing a high fever, rash, cough, runny nose, and watery eyes. About 8% of children will also get an earache, and about 6% will get pneumonia. 1 in every 1,000 children with the measles can develop brain inflammation (encephalitis), causing convulsions, deafness, or brain damage. About 2 in every 1,000 cases are fatal. Pregnant women who catch the measles can have a preterm birth, or even lose the fetus (miscarriage).
  • Mumps causes fever, headache, and salivary gland inflammation. About 1 in 10 children with mumps have meningitis (inflammation of the covering of the brain and spinal cord) or, sometimes, encephalitis (inflammation of the brain itself). This can cause deafness, but permanent damage is rare. 1 in 10 men who get mumps will have their testicles swell and become painfully inflamed, which may lead to infertility.
  • Rubella – also called "German measles" – is usually a mild disease, causing slight fever and a rash for 2 or 3 days. Adults can also experience temporary arthritis and swollen glands at the back of the neck. Women who get rubella early in pregnancy have a greater than 80% chance of having babies with severe birth defects, including blindness, heart and major artery damage, deafness, brain damage, and brains that are smaller than normal. Rubella during pregnancy may also lead to miscarriage.

Meningitis caused by the meningococcus bacteria (Neisseria meningitides) is a rare but serious disease associated with inflammation of the membrane covering of the brain and spinal cord. Symptoms include sudden onset of fever, intense headache, stiff neck, nausea and vomiting, and sensitivity to light. About 10% to 15% of everyone who gets bacterial meningitis dies from it, but if the bacteria enters the blood, the death rate is up to 40%. About 20% of the survivors are left with permanent damage (loss of hearing, brain damage, or loss of limb).

Pneumonia is a lung infection that may be caused by bacteria, viruses, or fungi. It occurs in both children and adults. Pneumonia may develop at the same time as another infection, such as the flu, whooping cough, measles, or chickenpox. Symptoms include coughing up mucus, difficulty breathing, chest pain, fever, and chills. Serious cases of pneumonia may lead to hospitalization. Pneumonia caused by bacteria may be treated with antibiotics. Some cases of pneumonia may be prevented by vaccines, such as the pneumococcal vaccine, the Hemophilus influenzae type B (HiB) vaccine or the influenza vaccine.

Polio (poliomyelitis) is caused by a virus that lives in the nose, throat, and intestines of infected people. The virus is contagious even when a person doesn't have any symptoms. Milder forms usually last a few days, causing fever, nausea, headache, sore throat, stomach ache, and sometimes pain or stiffness in the neck, back, and legs. A more serious form, paralytic polio, also causes severe muscle pain. About half of people with paralytic polio are permanently paralyzed within a week of the start of symptoms. Others may recover completely or have mild physical disabilities.

Tetanus – also known as "lockjaw" – is caused by a bacterium commonly found in soil, manure, and the digestive tracts of people and animals. When the bacteria enter deep cuts or wounds that are difficult to clean, they can multiply and produce a toxin. The toxin acts as a poison for the nervous system, causing headache and muscular stiffness in the neck and jaw. As the toxin accumulates, it causes spasms in the jaw, neck, and limbs, rigidity in the abdominal muscles, and convulsions. Symptoms are painful and last for weeks. This condition often requires hospitalization and carries a high fatality rate.

Whooping cough (pertussis) is caused by a bacterium that infects the mouth, nose, and throat. It's highly contagious. It causes severe coughing that can make it difficult to eat, drink, and breathe. Young children, especially infants under one year of age, are most susceptible to getting pertussis. The infection is often serious, leading to hospitalization. Complications may include pneumonia, convulsions, and, rarely, inflammation of the brain (encephalitis) or death.

Rotavirus is a common cause of gastroenteritis in children. Routine vaccination against rotavirus has resulted in decreased incidences of and hospitalisations due to gastroenteritis, as well as, decreased infant deaths due to severe diarrhea. Unlike other vaccines that are given as injections, the vaccine against the rotavirus is given by mouth. The vaccine is not always completely protective, but vaccinated children have much milder cases if they do get the infection.

Influenza virus causes severe illness and pneumonia in all ages, but children and seniors are most at risk for serious complications. Vaccination is recommended annually for everyone over 6 months of age at the beginning of the flu season (usually in October or November). Annual revaccination is required because the type A flu virus changes its characteristics (mutates) yearly.

Human papilloma virus (HPV) is a virus that is spread through sexual contact. It is one of the most common sexually transmitted infections. There are many different types of HPV. Infection with certain types of HPV can cause genital warts, and can also cause certain cancers including cervical, penile, anal and throat cancer. Vaccination against HPV can prevent these cancers from developing. For maximum protection, both boys and girls should receive the vaccine around ages 11 or 12, although vaccination may be started as early as age 9.

Coronavirus disease 2019 (COVID-19) is a type of infection spread directly from person to person via respiratory droplets and aerosols, often from coughing or sneezing. There are many types of COVID-19 variants, such as Omicron. COVID-19 is highly infectious and can lead to worse outcomes such as hospitalization for people with risk factors like a weakened immune system. Everyone 6 months of age and above is advised to receive a vaccination against COVID-19, as well as any booster doses that they may be eligible for.   

Scheduling Immunization

Vaccinations are generally available as a series of injections, sometimes combining several vaccinations. They're given at different times during infancy and childhood, usually during routine visits to a doctor's or pediatrician's office. Records of childhood vaccinations are often mandatory for children when they begin school.

Side effects of vaccination are usually mild, but may include fever, soreness at the site of injection, tiredness, and a rash. These pass within a couple of days and serious complications are very rare.

Under certain conditions, vaccinations should be delayed or stopped. If your child has severe allergic reactions to a particular vaccine, remaining injections may have to be discontinued. If your child has other allergies – to antibiotics or eggs, for instance – talk to your doctor about whether this affects vaccination. A child who's sick or whose immune system is compromised might have to postpone getting a regularly scheduled shot. Missing an injection doesn't require you to start most vaccination series from scratch.

Hepatitis B (HepB or HBV) vaccine is recommended for all children and is increasingly being given shortly after birth. However, in some areas, it is not given until children reach grade 7. For newborns, the first shot is given during a visit to a doctor or pediatrician after the baby has left the hospital, usually before the baby is 2 months old. The second shot is given at least 4 weeks after the first. The third shot is usually given 2 months after the second shot and at least 4 months between the first and third. Mothers should always be routinely tested for hepatitis B in pregnancy and, if positive, the newborn should receive the hepatitis B immune globulin. This helps protect the infant from hepatitis B until the immunizations start working. The infant should then receive three shots of hepatitis B vaccine on the regular schedule.

A diphtheria, tetanus, and whooping cough vaccine is usually administered at the age of 2, 4, 6, and 18 months. A booster shot is given at the age of 4 to 6 years. Another booster shot against tetanus and diphtheria is then given around the 15th birthday. After this, booster shots for tetanus and diphtheria are required every 10 years for continued protection.

Hemophilus influenza type b (Hib) vaccine is usually administered at 2, 4, and 6 months of age, and then another booster shot is given around the age of 18 months.

Immunization against polio alone is given in the form of an inactivated poliovirus vaccine at the age of 2, 4, and 6 months, and then again at 18 months or between 4 and 6 years. This vaccine is combined with the diphtheria, tetanus, and whooping cough vaccine. Oral polio vaccines used to be more common in developed countries, but they carried a very small risk of causing paralytic polio.

Measles, mumps, and rubella (MMR) vaccine is given between 12 and 15 months. A second injection is given either with the next set of vaccinations due at 18 months, or between 4 and 6 years old, before a child begins school.

Chickenpox immunization, or varicella vaccine, is recommended for anyone over 12 months of age who has never had chickenpox. 2 doses of vaccine are given. For children, the first dose is given at 12 to 18 months of age and the second dose at 4 to 6 years of age. For people 13 years of age and over, the 2 doses are given at least 4 to 6 weeks apart.

Pneumococcal conjugate vaccine is recommended to help protect against pneumococcal infections, which may include a variety of diseases such as pneumonia or ear infections. The recommended schedule for infants is 4 doses of the conjugate vaccine administered at 2, 4, and 6 months old and again between 12 and 15 months old.

Rotavirus is a vaccine given as 2 separate oral doses. The first dose should be given between 6 and 15 weeks with the second dose completed by the age of 32 weeks.

Routine immunization against meningitis caused by Meningococcus type C is also recommended for all children. The timing of vaccination varies depending on age, risk, and geographic region.

The influenza vaccine, available in the early fall each year, is recommended for children aged 6 months and older. Children between the ages of 6 months to under 9 years receiving the flu shot for the first time should receive 2 doses, given at least 4 weeks apart. Children who have had one or more doses of the flu shot in the past, need only one dose per year.

Vaccination against human papillomavirus (HPV) is recommended in for both males and females, usually starting at ages 11 to 12, although it may be started as early as 9 years of age. It is given as a series of 2 to 3 injections, depending on the age when the vaccine is started.

COVID-19 vaccines are recommended children aged 6 months and older. The number and timing of recommended doses vary for each person based on their age, pre-existing medical conditions, and whether they've recently been infected with COVID-19. Booster doses are recommended to help maintain your body's protection against the virus and, in some cases, protect you against newer strains.

Concerns about Childhood Vaccinations

Health Canada states that vaccinations are one of the most cost-effective interventions available. However, some people are concerned about the side effects of immunization and are questioning the necessity of vaccinating their children. Others also question the need to continue to vaccinate children against diseases that are rare in Canada. It is important to understand the risks and benefits of immunization. To make an informed decision, speak with your doctor or pharmacist about your concerns.

Some of the concerns people have about immunization include:

  • Safety and long-term effects: There have been concerns that vaccines may increase the risk of SIDS (sudden infant death syndrome), asthma, and autism. When a child develops a health problem after receiving a vaccine, it is natural to wonder if there may be a link between the two. There are two kinds of links: either the vaccine did make the child more likely to develop the condition, or it was just a coincidence that both happened around the same time. Currently, the evidence shows that it is likely to be a coincidence and vaccines have not been shown to cause any of these conditions. Studies of large populations of children have failed to show an association between MMR vaccine and autism, and have concluded that the rate of autism in children has not increased since introduction of the vaccine.
  • "Overloading" the immune system: Some people feel that giving a child multiple vaccines at the same time can overload the immune system. Vaccines contain viruses or bacteria (whole or in parts) that have been altered so they cannot cause disease. Children are actually exposed to many viruses and bacteria each day through normal activities such as eating and playing. The number of viruses or bacteria a child is exposed to in a vaccine does not significantly add to the ones they are exposed to in everyday activities.
  • Effectiveness: People opposed to vaccines often claim that better hygiene and diets, not vaccines, are responsible for reducing the levels of childhood diseases. While better hygiene and nutrition can improve overall health and reduce the risk of some diseases, the decreases in rates of vaccine-preventable childhood diseases are mostly due to vaccination. For example, Hemophilus influenzae type b (Hib) disease was common until the vaccine was introduced in the 1990s. After that, the number of cases dropped dramatically. Since sanitation and nutrition are no better now than they were in the 1990s, it is unlikely that they are responsible for this large decrease in the rate of infection.

In Canada, the annual occurrence of vaccine-preventable diseases has fallen to a few dozen or none at all, depending on the disease. Canada has continual surveillance of vaccines marketed in this country. The safety of each production lot is closely monitored. Collaboration with provincial public-health networks has resulted in very high reporting rates when vaccine-related illnesses or complications occur.

The World Health Organization (WHO) also has an advisory body to monitor and evaluate global vaccine safety. Working with governments and international organizations, the WHO makes scientific recommendations concerning vaccination, based on international information and assessments.

Given the potential severity of many of the vaccine-preventable childhood diseases, immunization is considered by the medical community to be the safer decision. Though vaccination side effects do exist, they are minimal compared to the devastating toll widespread epidemics have had on populations, even in the 20th century.


Symptoms and Complications

Making the Diagnosis

Treatment and Prevention

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