SCHOOL-BASED IMMUNIZATION COVERAGE IN NOVA SCOTIA:

Transcription

1 SCHOOL-BASED IMMUNIZATION COVERAGE IN NOVA SCOTIA: February 18, 2015 Population Health Assessment and Surveillance

2 Acknowledgements Provincial surveillance of school-based immunizations would not be possible without the timely and complete reporting by public health professionals in the province. The Nova Scotia Department of Health and Wellness extends its thanks to all those whose contributions have helped make this report possible. For questions regarding this report, please contact: Population Health Assessment and Surveillance Nova Scotia Department of Health and Wellness PO Box 488 Halifax, NS B3J 2R8 Phone: (902) Fax: (902) School-based Immunization Coverage in Nova Scotia Page 1 of 13

3 Table of Contents Acknowledgements... 1 Introduction... 3 Methodology... 4 Limitations... 5 Tetanus, Diphtheria, and Acellular Pertussis (Tdap)... 6 Meningococcal Group C Conjugate (Men-C-C)... 7 Human Papillomavirus (HPV)... 8 Hepatitis B... 9 Adverse Events Following Immunization Discussion Appendix Number of Immunizations & Students Enrolled School-based Immunization Coverage in Nova Scotia Page 2 of 13

4 Introduction Delivery of vaccines via school-based immunization programs is an effective delivery model to reach the adolescent target population. A school-based delivery model provides equal access to immunization for the adolescent population (attending schools) and can reduce disparities in vaccine coverage. In Nova Scotia, the school based immunization program is the primary method of delivery of the following four publicly funded vaccines; Tetanus, Diphtheria, and Acellular Pertussis (Tdap) Meningococcal Group C Conjugate (Men-C-C) Hepatitis B Human Papillomavirus (HPV) The school based immunization program is delivered by Public Health Services to grade seven students within public and private schools and by community health nurses within First Nations schools onreserve. The vaccines are administered to both males and females, with the exception of the HPV vaccine, which is administered only to females. Monitoring immunization coverage rates provides important information for Public Health planning and decision making. Immunization coverage rates are a useful indicator of vaccine uptake within populations and of a population s susceptibility to vaccine-preventable diseases. In the Department of Health & Wellness set the following provincial targets for school-based immunization coverage rates: Tdap, Men-C-C, Hepatitis B 90% coverage HPV 80% coverage This report focuses on immunization coverage rates for the school-based program in Nova Scotia for the school year. Provincial and District Health Authority (DHA) coverage rates are presented for each vaccine. For vaccines requiring more than one dose, coverage rates per dose are presented. School-based Immunization Coverage in Nova Scotia Page 3 of 13

5 Methodology Coverage calculations: Immunization coverage rates are calculated as follows: Coverage rate (%) = # immunized (numerator) x 100 # of students in grade seven (denominator) Numerator: The number of students in grade seven who received the vaccine between September 1, 2012 and August 31, Grade seven was inferred based on age at the time of immunization, using a four year age range (11-14). School year was defined as September 1 to August 31 to allow for immunizations administered during the summer months. All school-based immunizations are entered into the Application for Notifiable Disease Surveillance (ANDS) by Public Health. Any notifications (e.g. reciprocal forms) that are received for immunizations delivered by other health care providers are also entered into ANDS by Public Health. The immunization data used in this report was extracted from ANDS and includes any immunization events entered on or before April 4, Denominator: The number of students enrolled in grade seven as of September 30, This includes all students enrolled, and may include individuals that did not require the immunization at the time of the program delivery (if they had already received the dose previously from a physician or outside of the province, etc.). The data on grade seven enrolment for the school-based program come from the Nova Scotia Department of Education and First Nations communities. For vaccines with multi-dose schedules (HPV and Hepatitis B), coverage is calculated for each valid dose and for the full series. Descriptions for valid doses are presented below (Table 1). Table 1: Description of valid doses for HPV and Hepatitis B vaccines HPV Hepatitis B Dose 1 # of students who received a dose of the vaccine in the specified school year. # of students who received a dose of the vaccine in the specified school year. Dose 2 # of students who received another dose of the vaccine >27 days after the first dose, in the specified school year. Dose 3 # of students who received a third dose > 111 days after the first dose, in the specified school year. # of students who received another dose of the vaccine >27 days after the first dose *Using valid doses excluded <10 records so is not considered a limitation causing data problems. Adverse Events Following Immunization (AEFI): The number of adverse events following immunization (AEFI) related to school-based immunizations are presented in the report. The AEFI data were extracted from ANDS. School-based Immunization Coverage in Nova Scotia Page 4 of 13

6 Limitations The numbers of students immunized within the school based program are extracted from ANDS for this report. Immunizations by providers other than Public Health are included if notifications have been received by Public Health and entered into ANDS. Notifications not received by Public Health will result in lower coverage rates. Denominator data on the number of students was based on September enrolment. By using September enrolment, the movement of students between DHAs could potentially result in a student immunization being counted in a particular DHA, but that student being reflected in the denominator of another DHA. Provincial coverage rates are not impacted by this potential limitation. Use of the September enrolment data assumes that all students who are enrolled in grade seven in the current school year are eligible for immunization. Students who were immunized in a previous school year (e.g. Hepatitis B for travel) have not been removed from the denominator. Therefore coverage rates presented in this report reflect the proportion of the grade seven cohort immunized in the current school year, not the proportion of the grade seven cohort who have up to date coverage of the four school-based vaccines. Methods to estimate up to date coverage are currently being explored. By estimating grade level based on a four year age group the potential exists to capture immunizations for students who may not be captured in the denominator. This would potentially inflate the coverage rates. School-based Immunization Coverage in Nova Scotia Page 5 of 13

7 Tetanus, Diphtheria, and Acellular Pertussis (Tdap) The Tdap vaccine is administered as a single dose and protects against Tetanus (Lockjaw), Diphtheria, and Pertussis (Whooping Cough). Diphtheria and Tetanus have essentially been eradicated in Nova Scotia. There have been no cases of Diphtheria in over a decade and only one case of Tetanus in the past five years ( : rate of 0.02 per 100,000). The province continues to see pertussis cases each year. Over the past five years ( ) there was an average of 10.6 cases per year (rate of 1.1 per 100,000). Coverage rates for Tdap vaccine are presented below (Figure 1 and Table 2). For the school year the provincial coverage rate was 91.9 %. This is similar to previous years and is above the provincial target of 90 percent. Over the past 5 school years ( to ) Tdap coverage ranged between 78.9 % and 93.2%. Figure 1: Tdap coverage rates (%) in Nova Scotia, to school year * * Between the and school years the immunization schedule varied as follows: : grade 7 and year olds, : grade 10, : grades 7&8, and beyond: grade 7. The NS coverage rate does not include data from DHA 7&8 because the year old cohort were immunized in the school year and therefore not captured in this analysis. During the reporting period Tdap coverage rates ranged from 88.2 % to 96.2% across the district health authorities (Table 2). Only two DHAs were slightly below the 90% target. Table 2: Tdap coverage rates (%) by DHA, DHA COVERAGE 1 - South Shore Health South West Health Annapolis Valley Health Colchester East Hants Health Authority Cumberland Health Authority Pictou County Health Authority Guysborough, Antigonish, Strait Health Authority Cape Breton District Health Authority Capital District Health Authority 91.9 NS 91.9 School-based Immunization Coverage in Nova Scotia Page 6 of 13

8 Meningococcal Group C Conjugate (Men-C-C) Meningococcal Group C Conjugate (Men-C-C) vaccine is administered as a single dose and protects against illness caused by the group C strain of meningococcus. It does not protect against other strains of this bacteria, or other organisms that cause meningitis or septicaemia. Over the past five years ( ) there has only been one case (rate of 0.02 per 100,000) of Invasive Meningococcal Disease identified as group C in Nova Scotia. There was one case of Invasive Meningococcal Disease during this same time period of unknown serogroup. Coverage rates for Men-C-C vaccine are presented in Figure 2 and Table 3. For the school year the provincial coverage rate was 91.0 %. This is similar to previous years and is above the provincial target of 90 %. Over the past 5 school years ( to ) Men-C-C coverage ranged between 79.3 % and 91.4%. Figure 2: Men-C-C coverage rates (%) in Nova Scotia, to * * Between the and school years the immunization schedule varied as follows: : year olds, : grade 10, and beyond: grade 7. The NS coverage rate does not include data from DHA 7&8 because the year old cohort were immunized in the school year and therefore not captured in this analysis. Across the district health authorities coverage rates ranged from 87.1 % to 95.3 % during the reporting period (Table 3). One DHA was below the ninety percent target. Table 3: Men-C-C coverage rates by District Health Authority, DHA COVERAGE 1 - South Shore Health South West Health Annapolis Valley Health Colchester East Hants Health Authority Cumberland Health Authority Pictou County Health Authority Guysborough, Antigonish, Strait Health Authority Cape Breton District Health Authority Capital District Health Authority 90.8 NS 91.0 School-based Immunization Coverage in Nova Scotia Page 7 of 13

9 Human Papillomavirus (HPV) Human Papillomavirus (HPV) vaccine is administered to female students as a series of three doses and protects against HPV, a common sexually transmitted infection. HPV vaccine protects against the most common types of HPV that infect the genital area, including the 2 types of HPV that cause 70 % of cervical cancer. HPV infection is not a notifiable disease in Nova Scotia (or Canada), however greater than 70 % of sexually active Canadians are estimated to have a sexually transmitted HPV infection at some point in their lives 1. The HPV vaccine was introduced into the school-based immunization program in the school year. Complete coverage rates per dose for HPV vaccine are presented in Figure 3 and Table 4. Coverage rates decreased for each dose. For the school year the provincial coverage rate for the complete series was 77.2 %. This is similar to previous years and is below the provincial target of 80 percent. Over the past 5 school years ( to ) full HPV coverage (all three doses) ranged between 59.8 % and 77.2%. Figure 3: HPV vaccine coverage rates (%) in Nova Scotia, to * * Between the and school years the immunization schedule varied as follows: : grade 7, : grade 10, : grade 7&8, & beyond: grade 7. Across the district health authorities, coverage rates (for the full series) ranged from 73.8 % to 86.0 % during the reporting period (Table 4). Four DHA s achieved the 80% target. Table 4: HPV coverage rates (%) by District Health Authority, DHA COVERAGE 1 - South Shore Health South West Health Annapolis Valley Health Colchester East Hants Health Authority Cumberland Health Authority Pictou County Health Authority Guysborough, Antigonish, Strait Health Authority Cape Breton District Health Authority Capital District Health Authority 75.2 NS School-based Immunization Coverage in Nova Scotia Page 8 of 13

10 Coverage Rate (%) Hepatitis B Hepatitis B vaccine is administered in the school program as a series of two doses and protects against the Hepatitis B virus. Hepatitis B is caused by contact with the blood or body fluids of someone who is infected. The annual rate of acute Hepatitis B infection in Nova Scotia is low. Over the past 5 years there has been an average of 2.6 cases per year (rate of 0.28 per 100,000). Complete coverage rates per dose for Hepatitis B vaccine are presented in Figure 4 and Table 5. Coverage rates for the complete series are lower than the rates for the first dose. For the school year the provincial coverage rate for the complete series was 79.1 %. This is similar to previous years and is below the provincial target of 90 percent. Over the past 3 school years ( to ) the coverage rate for the complete series of Hepatitis B vaccine ranged between 78.0 % and 79.8%. Figure 4: Hepatitis B vaccine coverage rates (%) in Nova Scotia, to * DOSE DOSE DOSE *In the school year Hepatitis B vaccine was administered as 3 doses of pediatric formulation (due to a global shortage of adult formulate). In the subsequent years it was administered as 2 doses of adult formulation. Hepatitis B vaccine coverage rates by DHA are presented in Table 11. Full coverage (complete doses) rates ranged from 76.0 % (DHA 7) to 88.4 % (DHA 4) across the DHAs. Table 5: Hepatitis B coverage rates (%) by District Health Authority, DHA COVERAGE 1 - South Shore Health South West Health Annapolis Valley Health Colchester East Hants Health Authority Cumberland Health Authority Pictou County Health Authority Guysborough, Antigonish, Strait Health Authority Cape Breton District Health Authority Capital District Health Authority 74.6 NS 79.1 School-based Immunization Coverage in Nova Scotia Page 9 of 13

11 Adverse Events Following Immunization In the school year there were six adverse events following immunization (AEFI) related to school-based immunizations that met the case definition for reporting. This represents 0.01 percent of all the school-based immunizations given in School-based Immunization Coverage in Nova Scotia Page 10 of 13

12 Discussion Coverage rates presented in this report are based on immunizations administered within a particular school year. As such they reflect the proportion of the grade seven cohort immunized in a given school year, rather than the proportion of the grade seven cohort who have up to date coverage of the four school-based vaccines. Methods to estimate of up to date coverage will continue to be explored for future reporting. Immunization targets were achieved for Tdap and Men-C-C in the school year, but targets were not achieved for HPV and Hepatitis B. Hepatitis B vaccine is frequently administered as part of travel related immunizations by providers other than Public Health. If Public Health was not notified of these immunizations or if these immunizations did not occur in the school year they would not have been captured in these analyses. It is likely that Hepatitis B coverage may be higher than reflected in the report. Between and coverage rates for the school-based program were consistent. Rates were lowest in the school year. In a one-year immunization catch-up program for Grade 10 students was planned in addition to grade seven students. Due to the Public Health response to H1N1 that year, there were insufficient resources to conduct immunization clinics for two grades, resulting in only grade 10 students being immunized in Lower coverage rates for that school year could be due to lower uptake among older students, although the focus on H1N1 immunization may have also played a role on uptake of school based immunizations. School-based Immunization Coverage in Nova Scotia Page 11 of 13

13 Appendix Number of Immunizations & Students Enrolled Table A1: Tdap immunizations & students enrolled by DHA, DHA # Immunized # Enrolled % Coverage NS Table A2: Men-C-C immunizations & students enrolled by DHA, DHA # Immunized # Enrolled % Coverage NS Table A3: HPV immunizations & students enrolled by DHA, DOSE 1 DOSE 2 DOSE 3 DHA # Immunized # Enrolled % Coverage # Immunized # Enrolled % Coverage # Immunized # Enrolled % Coverage NS School-based Immunization Coverage in Nova Scotia Page 12 of 13

14 Table A4: Hepatitis B immunizations & students enrolled by DHA, DOSE 1 DOSE 2 DHA # Immunized # Enrolled % Coverage # Immunized # Enrolled % Coverage NS School-based Immunization Coverage in Nova Scotia Page 13 of 13