July 6, 2023
As some vaccine preventable disease outbreaks - like measles, polio and diphtheria – have made headlines around the world in recent months, people may wonder why these outbreaks are occurring and if they are at risk. To understand the current situation, it is important to understand how vaccination works as a public health preventive measure.
Today, I invite you to join me on a journey to learn more about vaccines and why they matter. I am extremely thankful for Canada’s long history of strong vaccination programs and their impact on improving health and will share a few examples with you.
Vaccines – what have we achieved with them?
Vaccines have greatly contributed to saving lives and improving the health of people in Canada and around the globe by limiting or stopping the ongoing circulation of some serious infectious diseases. The World Health Organization estimates that vaccination prevents from 3.5 to 5 million deaths a year from diseases such as diphtheria, tetanus, pertussis, influenza, and measles, and early studies suggest that COVID-19 vaccines have also prevented millions of deaths worldwide. Thanks to vaccines, smallpox has been completely eradicated (meaning it no longer circulates and we don’t need to vaccinate against it anymore), and many other diseases have seen a significant reduction in their rates. Because vaccines help prevent and protect against certain diseases, vaccination for individuals of all ages is considered to be one of the best investments we can make to improve population health and reduce health care costs.
Vaccines – how do they work?
Vaccines work with the body’s natural defenses (the immune system) to make us less susceptible to infections and less likely to develop serious illness. Vaccines also decrease the chances of spreading infection from one person to another. Vaccination works by exposing our bodies to key parts of bacteria or viruses, called antigens, in a safe way so our immune system can develop an immune response against them. Later, if we are exposed to that same bacterium or virus, our immune system will be able to recognize the antigen and respond more quickly to help prevent us from getting the disease or from getting seriously ill if we do get the disease.
Some vaccines can help to create community immunity (also known as herd immunity). This means that the greater the number of people who have been vaccinated against a disease, the less chance there is of the disease spreading in a community. This helps protect people who are at higher risk of developing severe complications from vaccine preventable diseases, including people who can’t be vaccinated or for whom a particular vaccine may not work as well, such as people who are immunocompromised.
Let’s take a closer look at some of our available vaccines and the important impact they have had in Canada. In addition to those listed below, there are vaccines that can prevent against a number of other illnesses, such as certain types of pneumonia, meningitis, chickenpox, shingles, and hepatitis B, among others. There are also vaccines against specific respiratory viruses (such as influenza and SARS-CoV-2) and for travellers, depending on the country they are travelling to.
Measles can be a serious infection that can result in pneumonia and inflammation of the brain, leading to permanent brain damage and even death. It is also one of the most contagious diseases. Even a single case can spread quickly among people who are not vaccinated or previously infected. In a group of 100 people who have never had a measles infection, 95 of them need to be vaccinated to prevent measles from spreading. This is why population-level measles vaccination coverage has to remain high to prevent outbreaks.
Luckily, the measles-mumps-rubella (MMR) vaccine protects against three contagious viruses: measles, mumps, and rubella. In Canada, cases of measles, mumps, and rubella have decreased by 98% or more as a direct result of the introduction of those vaccines in the 1960s and their inclusion within routine vaccination programs.
However, global health organizations are warning that disruptions to vaccination pose a potential risk of significant measles outbreaks. Global measles incidence is increasing from the previous two years, when pandemic precautions prevented widespread measles outbreaks. In order to prevent a spike in measles cases, governments and organizations around the world will need to make a concerted effort to catch up on missing vaccinations.
Recognizing the risks of imported cases and potential for outbreaks, Canada continues to promote uptake of routine childhood vaccinations, working towards achieving 95% vaccination coverage with at least one dose of MMR vaccine for children 2 years of age and 2 or more doses for children 7 years of age by 2025. Our latest national data from 2021 show that uptake remains fairly stable over the past decade for children 2 years of age, with around 92% having received at least one dose of MMR in 2021. These results show that more work is required to encourage and facilitate uptake amongst households with lower incomes or lower education as well as amongst those in remote or very remote areas. Although not statistically significant, MMR coverage with 2 or more doses for children 7 years of age decreased from 83% in 2019 to 79% in 2021. Work continues across the country to reach the 95% coverage goal.
Polio is a highly infectious disease that affected various parts of the country in waves from the 1920s to the 1950s, with the worst year being 1953 when it claimed 500 lives and infected over 9,000 people in Canada. Although most people with polio do not become sick or had only mild symptoms, some experience paralysis as the virus attacks the spinal cord, with young children less than 5 years of age being particularly vulnerable. In severe cases, the disease can cause damage to the nerves controlling muscles around the lungs, which in the past led some people to have to rely on machines called “iron lungs” to survive. The development of polio vaccines, starting with the injectable Salk vaccine in the 1950s and followed by the oral Sabin vaccine in the 1960s, marked a significant breakthrough in efforts against polio. As a result of widespread use of polio vaccines, Canada was certified polio-free in 1994.
Today, the Global Polio Eradication Initiative is leading international efforts to completely eradicate polio worldwide. However, until the virus is eradicated globally, there remains a risk of contracting polio when traveling to countries with circulating polio virus. Therefore, polio vaccination will remain on the routine vaccination schedule for all children in Canada until polio has been eradicated and is no longer a threat globally. Canada is working towards achieving 95% vaccination coverage with at least three doses of polio vaccine for children 2 years of age by 2025. In 2021, 92% of 2-year-olds received at least three doses of polio vaccine, which was unchanged from 2019.
Tetanus, diphtheria, and pertussis vaccinations
Combination vaccines are available for children and adults to protect against tetanus, diphtheria, and pertussis (also commonly known as whooping cough). Cases of all three diseases have decreased by 95% or more in Canada because of routine vaccination programs.
Since 2018, the National Advisory Committee on Immunization as well as the Society of Obstetricians and Gynecologist of Canada have recommended that a pertussis-containing vaccine be offered during every pregnancy in Canada, regardless of previous vaccination history. Receiving a pertussis-containing vaccine during pregnancy helps protect newborns, who are at significant risk for serious illness from pertussis. Progress has been made to ensure pregnant people are informed of this recommendation, with good outcomes; pertussis vaccine coverage during pregnancy has increased from 44% in 2019 to 65% in 2021. However, continuous efforts need to be undertaken to inform and support this population to become vaccinated during their pregnancies to provide the best possible protection against pertussis for their newborn babies.
Tetanus, diphtheria, and pertussis vaccinations are recommended at various stages in the life course to maintain strong immune protection from these diseases over time. Presently, the only national vaccine coverage goal that Canada has reached - for any age group - relates to tetanus, diphtheria, and pertussis vaccination. Based on our most recent data (2021), 93% of children received at least one dose of a Tdap (tetanus, diphtheria and acellular pertussis) vaccine by their 17th birthday, which is higher than the coverage goal of 90%. It is important that we continue to strive for high coverage of these vital vaccinations.
Human papillomavirus (HPV)
HPV is a virus that has a number of types, some of which can cause skin or mucous membrane warts and others which can lead to several types of cancer, including cervical cancer and cancers of the mouth and throat (oropharynx), anus, vulva, vagina and penis.
Fortunately, free HPV vaccines aimed at the HPV types that most commonly cause cancer and genital warts are offered through school-based programs and catch-up programs for children and youth in all provinces and territories in Canada. The HPV vaccine is a critical component of the Action Plan for the Elimination of Cervical Cancer in Canada, 2020-2030. This plan aims to eliminate cervical cancer by 2040 using strategies such as HPV immunization and screening.
Canada's goal is to have 90% of 17-year-olds fully vaccinated with the HPV vaccine by 2025. According to our most recent national childhood vaccination coverage data, HPV vaccine coverage among 14-year-olds has increased from 80% in 2019 to 84% in 2021, driven by an increase among males from 73% to 81%. This increase further narrows the coverage gap between male and female children, whose HPV vaccination coverage (86%) has not changed during this same period.
Thank you for joining me on this journey. Our robust vaccination programs have been critical for limiting the occurrence and spread of many serious vaccine-preventable diseases in Canada. As the potential for outbreaks continues, it’s vital that each of us stay up-to-date with all recommended vaccinations to continue to help keep ourselves and our communities healthy.
The need for high vaccine uptake also reinforces the importance of ensuring accurate, appropriate, and timely information about vaccines is available to the public. Providing the public with credible information from trusted sources helps combat inaccurate or misleading information about vaccines. Below are links to a range of vaccine-related resources for different age groups. If you have any specific questions about vaccines for you or your family, please reach out to a healthcare provider or your local public health unit, as they can support you in finding the credible information you need to answer your questions.
For more information on vaccination in Canada: