Vaccines are biological medications that make the body’s immune (defense) system react. Antigens are the substances in a vaccine that create this response. In vaccines, antigens could be:
By itself, an antigen cannot cause disease. However, exposure to it stimulates the immune system, creating antibodies. These antibodies remember the antigen, so that if you are exposed to the actual disease, your immune system will respond. This helps prevent you from getting the disease, or lessens the severity. It also helps protect others who are vulnerable or unable to be vaccinated.
In Canada, most babies and school-aged children receive a series of vaccines. However, some vaccines require a ‘booster.’ Additional vaccine is given later in life to remind the immune system of the disease. It helps extend the protection.
Some adult vaccines are available to everyone. Others are only given in specific risk situations.
The seasonal influenza (flu) vaccine is perhaps the most common one that adults should receive. Influenza is an illness caused by a virus. It involves symptoms like fever, chills, cough, congestion, and fatigue. If the immune system is already weak, flu can lead to more serious illness, most commonly pneumonia. In some cases, it can lead to death.
The flu virus can change vastly within the span of a year. As a result, adults need an updated flu shot each year. The latest version helps protect against certain strains of the flu, or lessens the severity. It also prevents the spread of flu to vulnerable people and those who have not received the flu vaccine. The most commonly used injected flu vaccine contains three strains of dead (inactivated) flu virus.
A version of the vaccine is available as a nasal spray. It contains live, weakened strains of the flu virus. It should only be given to healthy people between the ages of two to 59, who do not have chronic medical conditions, are not pregnant, and will not be in close contact with anyone who has a weakened immune system.
Pneumococcal disease is caused by Streptococcus pneumonia bacteria. It can cause pneumonia (occasionally after a person has had the flu). It may also lead to other serious diseases like meningitis. This injected vaccine should be given to people aged 19 to 64 who are residents of a care home. Other recommended recipients include people who smoke, alcoholics, and those with asthma and chronic illnesses who are more likely to get an infection. A booster should also be given to people over age 65. A maximum of two doses are recommended in a lifetime.
The varicella zoster virus primarily causes chickenpox infection. It sometimes leads to more serious complications or other infections. The injected varicella vaccine contains a live, weakened version of the virus. Mostly, it is given to children who have not had chickenpox. It is given in two doses, at least six weeks apart. Adults who have not had the disease may also receive it.
Once a person has been exposed to the varicella zoster virus, it continues to live inactive in the body. Sometimes, if the immune system becomes weakened, this virus can reappear as shingles (herpes zoster). Shingles cause a painful rash and scarring, and may lead to other infections or long-term pain.
The injected herpes zoster vaccine contains a live, weakened virus in a higher strength than the varicella vaccine. It is approved for adults over age 50. If you have had chickenpox in the past (and most adults have), you should receive this vaccine. The vaccine can also lessen the severity and duration of shingles. Someone who has had shingles before will be less likely to experience it again. If you have had an active shingles infection, wait at least a year before being vaccinated. At this time, booster doses are not recommended for everyone. Only a single dose would be given in a lifetime.
Tetanus, diphtheria, and pertussis are all diseases caused by bacteria.
Vaccines for adults include Tdap (which protects against tetanus, diphtheria, and pertussis), and Td (which protects against tetanus and diphtheria). For people over age 11 who have not had Tdap, a single dose is recommended. After that, a Td booster should be given every 10 years. It is especially important that adults in close contact with children remain up to date on the Tdap vaccine. Babies and children are at particular risk when exposed to pertussis.
Hepatitis A is a virus that causes fever, nausea, jaundice, and liver problems. Those with chronic liver disease or who are likely to come into contact with hepatitis A should get the vaccine. For instance, IV drug users, travellers to areas with higher rates of hepatitis A, and people who may be exposed
at work are at higher risk. It is given by injection, in two doses spaced six to 12 months apart.
Hepatitis B can lead to chronic liver problems, liver cancer, and death. All high-risk adults should receive the hepatitis B vaccine, injected as a three-dose series. Second and third doses are given at one and six months after the first dose. For some people, a rapid course of four doses can be given within a shorter timeline. Hepatitis A and B vaccines are also available as a combined vaccine, given at the same time.
Human papilomavirus (HPV) causes infection with symptoms ranging from common warts to genital warts and certain cancers. The more serious strains are spread through sexual contact. Two vaccines are available. Both protect against the two strains that most commonly cause cancers. One also guards against two strains of virus linked to genital warts. Both are recommended for females from nine to 26 years of age, and those over age 27 who are at ongoing risk of exposure to HPV. A four-strain vaccine is also recommended for boys and men from nine to 26 years of age. Both vaccines are injected as a three-dose series. The initial dose is followed by another vaccination a month or two later, then a final booster six months after the first dose.
Measles, mumps, and rubella are infections that can cause mild to serious complications. The injected MMR vaccine helps to protect from all three illnesses. Children need to be vaccinated for these diseases. Adults at high risk include health care workers, university students, and international travellers. Women of childbearing age who are neither pregnant nor immune to rubella also require vaccination.
If you are unsure of whether you are immune, talk with your health care provider. Adults born in 1970 or later who have not had the MMR vaccine should receive it. If other risk factors exist, they may receive a second dose.
Current information on Canada’s vaccine guidelines and schedules:
Canadian information about vaccines for various groups:
Neisseria meningitidis is a type of bacteria that causes meningitis. The most common symptoms of meningitis include sudden high fever, headache, and neck stiffness. The chance of death can be high. Adolescents up to 24 years of age are one target group for vaccination. Others include those who lack certain antibodies, have HIV or a spleen that does not work (asplenia), who travel in certain high risk areas, or could be exposed at work. For adults at high risk of exposure or serious disease, a booster may be required every five years.
Hib bacteria can cause bacterial meningitis. The illness can lead to serious mental and physical complications and death. All babies need this vaccination, as well as some adults at high risk for Hib. These include people with no spleen function, sickle cell disease, Hodgkin’s disease, hematologic neoplasms (blood cancer), internal organ transplants, severely suppressed immune systems, HIV, or cochlear implants.
Vaccinations are a necessary part of staying healthy. Keeping them up to date protects not only yourself, but those around you. Your vaccination status can be checked by your doctor, pharmacist or public health clinic. This health care professional will work with you to determine which vaccines are recommended based on your own personal health needs.