[Table of Contents]

Volume: 23S4 - May 1997

Canadian National Report on Immunization, 1996

11. Activities Related to the Elimination of Polio and the Report of Working Group on Polio Elimination

11.1 Activities leading to polio elimination

The historical and recent epidemiology of poliomyelitis in Canada is described in the preceding section, "Epidemiology of Selected Vaccine-Preventable Diseases." Poliomyelitis was under control in Canada by the early 1970s, mainly through extensive immunization, improved sanitation, and surveillance. A total of 56 cases of poliomyelitis were reported from 1965 to 1995; 35 (63%) were due to wild virus infection and the remaining were associated with the use of OPV.

Starting in 1975, wild virus cases were identified as indigenous or imported. Of the 15 wild virus cases reported since 1975, only one (in 1977) was the result of indigenous wild virus infection. The last case of wild paralytic poliomyelitis in Canada occurred in 1988 as a result of virus importation. Wild polio virus was imported from the Netherlands to Canada in 1978-1979⁽¹⁸⁾ and in 1993⁽¹⁹⁾. Both these importations were linked to outbreaks in religious communities in the Netherlands; outbreaks in Canada were limited to similar closed communities (i.e those that do not accept routine immunizations for religious reasons). In the earlier importation, 11 paralytic cases occurred in British Columbia, Ontario, and Alberta. No clinical cases resulted from the 1993 importation to southern Alberta.

In 1989, NACI established a committee to review potential cases of paralytic polio for classification as wild or vaccine-related and to monitor the importation of wild polio virus⁽³²⁾. With increasing efforts in the American Region to meet the PAHO goal of regional elimination by 1995, it was imperative that Canada formally evaluate poliomyelitis surveillance and gather evidence for a certification of polio elimination.

In October 1993, the Advisory Committee on Epidemiology (ACE) convened a meeting to discuss the importation of wild polio virus from the Netherlands. Based on ACE recommendations, the Working Group on Polio Elimination was established in 1994. The Working Group reviewed all reported cases of suspected paralytic poliomyelitis and monitored continuing evidence for the elimination of polio in Canada.  The Working Group on Polio Elimination and the Division of Immunization, LCDC, prepared documentation on the elimination of polio for a National Certification Commission. Upon the Commission's favourable review of the situation and its report to the International Certification Commission, Canada and the rest of the American Region was certified as polio-free in September 1994. This was three years after the last indigenous wild case of poliomyelitis was reported in the Region.

Routine childhood immunization against poliomyelitis is still recommended because of the risk of importation of wild virus from other countries. Relatively high coverage rates have been maintained (approximately 90% for three or more doses of polio vaccine by 2 years of age). Paralytic poliomyelitis remains as a nationally notifiable disease in Canada; however, no cases due to wild virus have been reported since the imported case in 1988. In March 1996, wild virus importation from India was detected in an asymptomatic 15-month-old boy following a trip to that country⁽²⁰⁾. Although no paralytic disease occurred, the incident emphasizes the importance of continuing routine immunizations and surveillance activities until the global eradication of polio is achieved.

11.2 Report of the Working Group on Polio Elimination

In its first year, the Working Group on Polio Elimination collaborated with the National Certification Commission (established according to PAHO recommendations) in preparing a report on the evidence for the elimination of indigenous poliomyelitis in Canada. Polio surveillance had been enhanced in 1992 through the inclusion of active surveillance for AFP; admissions to pediatric hospitals in the IMPACT network were monitored. As well, all provincial laboratories were asked to refer polio virus isolates (whether or not they were obtained from symptomatic patients) to the National Reference Centre for Enteroviruses in Halifax for typing. In addition, LCDC conducted surveys to obtain information about levels of polio immunization in 2-year-olds in Canada.

To ensure that Canada continues to be polio-free, the Working Group currently monitors surveillance activities for potential cases of poliomyelitis. The Working Group meets at a formal annual meeting and additional teleconference meetings are held as required throughout the year to evaluate reported cases of suspected paralytic poliomyelitis.

AFP surveillance has been further enhanced through the CPSP established in January 1996, which has been described previously in the section, "Canadian Paediatric Surveillance Program." The National Reference Centre for Enteroviruses continues laboratory surveillance to detect Sabin strains of polio although this has declined since most provinces and territories no longer use OPV. The coincidental finding of an imported wild type polio virus in 1996 supports the effectiveness of the laboratory surveillance program. Age-appropriate coverage levels for polio vaccination at 2 years of age remain at approximately 90%. The Working Group recently developed a protocol for the investigation and reporting of suspected paralytic poliomyelitis, including AFP cases for those < 15 years of age. This protocol should serve as a standard guide to health units and further enhance the surveillance of poliomyelitis in Canada.

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