Immunization is “one of the most successful and cost-effective health interventions known”1, and has been heralded as one of the top ten public health achievements of the 20th century.2 The advent of vaccines and publicly-funded immunization programs have substantially reduced the number of reported cases of several diseases of public health significance, including measles, mumps, polio, and pertussis (whooping cough).
For example, in the past measles was considered a common childhood infection. In the 30-year period from 1929 to 1958, an average of more than 48,100 measles cases was reported across Canada each year3, with large-scale outbreaks occurring every two to three years.4 A vaccine to protect against measles was developed in the 1960s, and a publicly-funded measles immunization program was introduced in the 1970s. Since that time, the number of measles cases reported in Canada has substantially declined; in the most recent ten years of national data available, an average of 174 measles cases was reported annually.3
Thanks in part to this type of publicly funded immunization program, Canada has achieved elimination status for measles, as well as rubella, and polio.5 Several other diseases, including diphtheria and tetanus, are now classified as ‘low level incidence’.5
Despite these important gains, there is room for improvement in immunization coverage at a local, provincial, and national level. Immunization coverage for many vaccine preventable diseases remains below national targets in Canada5 and Ontario.6 Among 7-year old students in Middlesex-London schools, coverage for diphtheria, meningococcal C, pertussis, polio, tetanus and varicella (chickenpox) all increased between the 2013/14 and 2016/17 school years. However, in the most recent school year, immunization coverage for all diseases of public health significance was below the national target of 95%, which means that coverage in this age group was less than optimal to provide population-level protection.
Immunization coverage among 17-year old students in Middlesex-London schools was relatively stable or decreased between the 2013/14 and 2016/17 school years. In the most recent school year, though, coverage for measles, mumps, and rubella all exceeded the national target of 95%. Ongoing vaccination efforts and monitoring of immunization coverage is needed to ensure that this high level of coverage is sustained.
School-based immunizations for hepatitis B, human papilloma virus (HPV) and meningococcal ACYW-135 are another part of the Ontario publicly funded immunization program. Between the 2013/14 and 2016/17 school years, immunization coverage for meningococcal ACYW-135 increased among 12-year old students in Middlesex-London schools, while coverage for hepatitis B and HPV both decreased. Up-to-date coverage for all three vaccines is below the national target of 90% in the most recent school year, reinforcing the need for ongoing education about and promotion of these important vaccines.
Seasonal influenza immunization coverage among staff at long-term care homes (LTCH) and hospitals in the Middlesex-London region is an important means to help prevent influenza transmission in these facilities. However, staff influenza immunization coverage estimates have decreased since 2013/14 for hospital staff and since 2014/15 for LTCH staff, and were in the range of 55.0% to 57.0% in the most recent season.
Monitoring adverse events following immunizations (AEFI) is an integral part of all immunization programs, both to ensure the ongoing safety of vaccines and to promote public confidence in them. The reporting rate of AEFI among Middlesex-London residents was lower than in Ontario. At 0.4 reported AEFI per 100,000 population in 2017, AEFI may be considered quite rare in the Middlesex-London region.
The World Health Organization estimates that 1.5 million deaths could be avoided if immunization coverage for vaccine preventable diseases was improved.7 With the success of publicly funded immunization programs in reducing the incidence of vaccine preventable diseases, there may be “a tendency to underestimate the risks of vaccine-preventable diseases and overestimate the risks of vaccines”.8 Indeed, the public health threat of diseases that can be prevented through vaccination remains present. Maintaining and improving immunization coverage is an important health intervention that must continue well into the 21st century.
1. World Health Organization. Global vaccine action plan 2011-2020 [Internet]. Geneva (CH): World Health Organization; 2013 [cited 2019 Mar 26]. 77 p. Available from: https://path.azureedge.net/media/documents/OTP_dov_gvap_2011_20.pdf
2. Centers for Disease Control. Ten great public health achievements – United States, 1900-1999. MMWR Morb Mortal Wkly Rep [Internet]. 1999 Apr 2 [cited 2019 Mar 26];48(12);241-3. Available from: https://www.cdc.gov/mmwr/preview/mmwrhtml/00056796.htm
3. Reported cases from 1924 to 2016 in Canada – Notifiable diseases on-line [Internet]. Ottawa (ON): Public Health Agency of Canada.1924 – 2016 [modified 2018 Nov 25; cited 2019 Mar 19]. Available from: http://diseases.canada.ca/notifiable/charts?c=pl
4. Katz SL, King K, Varughese P, De Serres G, Tipples G, Waters J, Members of the Working Group on Measles Elimination. Measles elimination in Canada. J Infect Dis [Internet]. 2004 May [cited 2019 Mar 26];189(1 Suppl):S236-42. Available from: https://doi.org/10.1086/378499
5. Public Health Agency of Canada. Vaccine preventable disease: surveillance report to December 31, 2015 [Internet]. Ottawa (ON): Public Health Agency of Canada; 2017 Nov [cited 2019 Mar 26]. 60 p. Available from: https://www.canada.ca/en/public-health/services/publications/healthy-living/vaccine-preventable-disease-surveillance-report-december-31-2015.html#a311
6. Ontario Agency for Health Protection and Promotion (Public Health Ontario). Immunization coverage report for school pupils in Ontario: 2016-17 school year [Internet]. Toronto (ON): Queen’s Printer for Ontario; 2018 [cited 2019 Feb 12] 65 p. Available from: https://www.publichealthontario.ca/-/media/documents/immunization-coverage-2016-17.pdf?la=en
7. World Health Organization [Internet]. Geneva (CH): World Health Organization; c2019. Immunization coverage; 2018 July 16 [cited 2019 Mar 25]; [about 5 screens]. Available from: https://www.who.int/news-room/fact-sheets/detail/immunization-coverage
8. Public Health Agency of Canada [Internet]. Ottawa (ON): Public Health Agency of Canada; [modified 2019 Mar 28]. Canadian immunization guide; [modified 2018 Jan 24; cited 2019 Mar 25]; [about 2 screens]. Available from: https://www.canada.ca/en/public-health/services/canadian-immunization-guide.html
Last modified on: May 6, 2019