In , before the vaccine became available, visits to doctors' offices due to chickenpox were 25 per 1, children. In , seven years after the publicly funded varicella vaccination program began, that figure dropped to 3.
The rates of hospital ER visits and hospitalizations saw similar declines, and chickenpox-associated skin and soft tissue infections declined significantly, especially in kids under Initially, children were given one dose of the varicella vaccine.
But in , doctors began administering two shots — at 15 months old and between age four and six — after research showed the double-dose regimen was better at preventing outbreaks in schools and other settings where groups of children come in close contact. In Ontario, almost 78 per cent of five-year-old kids are known to have had at least one shot of the vaccine. Most provinces cover the cost of vaccination to prevent chickenpox, and these programs even help those who haven't been immunized because of the "herd immunity" phenomenon — which makes it more difficult for the virus to keep circulating and infecting people within the community.
Such herd immunity is also important for helping to prevent the spread of chickenpox due to imported cases, such as the Mexican soccer player who was diagnosed with the virus and isolated herself shortly after arriving in Toronto to compete in the Pan Am Games. Pseudonyms will no longer be permitted. By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses.
Please note that CBC does not endorse the opinions expressed in comments. Outlines a study which confirmed chickenpox as one of the single most important risk factors for acquisition of serious group A streptococcal infection which can lead to more serious illnesses, including flesh-eating disease in children. The purpose of this document is to review information on the epidemiology of varicella, compare the effectiveness of one dose of varicella vaccine with two doses, and to consider a potential change to the current National Advisory Committee on Immunization NACI recommendation for a one-dose childhood varicella vaccination program.
Provides a broad measure of coverage of six vaccinations influenza, pneumococcal disease, hepatitis A and B, pertussis, varicella, and tetanus among the adult Canadian population.
Describes a study which examined trends in varicella-related hospitalization rates and associated charges before and after the introduction of varicella vaccine. Assesses whether the effectiveness of varicella vaccine is affected either by time since vaccination or by age at the time of vaccination.
Reviews the diagnostic features of necrotizing fasciitis and analyzes treatment methods to control and eradicate this infection. Autoimmune disease. Adult immunization. Counselling the public. Cost effectiveness. Vaccine coverage. Hepatitis A. Hepatitis B. Haemophilus influenzae type B Hib. Human Papillomavirus HPV. Herpes Zoster. Influenza resources for professionals. The highest age-specific rates of medically-attended varicella were among children aged 1—4 years for office visits and ED visits Although infants accounted for only 5.
Crude annual incidence rates of pediatric varicella office visits, ED visits, and hospitalizations are shown in Fig 1A, 1B, and 1C. Age-specific annual declines in varicella office visits were 7. Incidence rates of varicella office visits, ED visits, and hospitalizations were greatest in the pre-varicella vaccine era Table 1. Although the IRRs calculated for hospitalizations were less than one for each of the comparisons, none reached statistical significance. Males accounted for a In contrast, the corresponding rates were 0.
The highest age-specific incidence of SSTI hospitalization during the study period was 7. Since , there have been seven or fewer children aged 1—4 years hospitalized with SSTI each year.
Varicella-associated ICU admissions occurred infrequently. For 1—4 year olds, incidence rate of varicella-associated ICU admissions ranged from 1. The overall incidence of complicated varicella admissions declined during the study period.
Rates during each era are shown in Table 1. Median ages of varicella cases over the entire study period were 5. The significant increase in the median age of children with varicella office visits from the pre-vaccine era to the post vaccine era was approximately 11 months. As seen in Table 2 , throughout the eras, median ages were older among those seen for ambulatory care office visits and ED visits versus among inpatients hospitalizations, SSTI and ICU admissions.
There were 53, incident office visits, 5, incident emergency department visits, and incident hospitalizations for herpes zoster among Ontario children aged 5—17 years during the study period. The proportion male was Greater average annualized age-specific rates of herpes zoster office visits and ED visits were observed among those aged 12—17 years In contrast, the rate of hospitalization was similar between the two age groups 1.
Yearly changes in rates of herpes zoster among children aged 5—17 years varied by clinical setting Fig 4. When the three eras pre-vaccine, privately-available, and vaccine program were examined for children aged 5—17 years in all three clinical settings, the IRRs comparing the incidence of herpes zoster in the period of private availability to the pre-vaccine era and the IRRs comparing the the varicella program era to the pre-vaccine period yielded no significant differences.
Comparisons of IRRs across the three periods in all three clinical settings were no different for 0—17 year-olds versus 5—17 year-olds i. Further, it appears changes in varicella epidemiology attributable to an immunization program have occurred.
These include reduction in complicated disease, a shift to older age at infection i. Rates of medically-attended paediatric varicella have declined since the previous Ontario analysis, whose last year of data was FY These reductions suggest ongoing immunization program success. In addition, although office visits decreased non-significantly based on IRR between the program and private periods and no IRRs for hospitalizations were significant non-significant findings may be due to vaccine use and early impact on severe [i.
Cost and public perception of varicella may have contributed to limited vaccine uptake see vaccine sales data below , and subsequent impact, during the privately-available period. The ability to prevent necrotizing fasciitis was an impetus for routine childhood varicella vaccination programs and we have shown a decline in varicella-associated SSTIs with the introduction of publicly-funded varicella vaccine in Ontario.
The relationship between varicella vaccine and subsequent herpes zoster among recipients, as well as herpes zoster in the population at-large, is not well understood. While some have observed an increase in herpes zoster among immunized or immunization-eligible children [ 14 ], most have not [ 1 , 11 ,— 13 ]. Our results provide reassurance that there has not been an increase in the incidence of pediatric herpes zoster associated with the introduction of publicly-funded varicella vaccine.
The increase in ED visits among 5—17 year-olds, which was not seen in the secondary analysis that included children under 5 years of age warrants ongoing study of herpes zoster, a condition that likely requires a longer observation period to determine if its incidence has been altered.
Further, there may be a role for chart-review validation of pediatric herpes zoster cases found in administrative databases to determine if the cases are clinically compatible with herpes zoster.
There are limitations to the present study. Medically-attended disease does not represent the true extent of pediatric varicella [ 25 ] and we were unable to accurately determine incidence of varicella. At the time of study, we could not use health care administrative data to assess the receipt of varicella immunization and Ontario does not have a registry of individual-level immunization information. As such, we could neither assess immunization coverage nor effectiveness.
Our conclusions with respect to herd immunity rely on the assumption that varicella vaccine is given to the target age group through the publicly-funded program. This assumption is supported by estimates of coverage and vaccine sales data. First, immunization coverage of school pupils is assessed annually through aggregate reports from local public health units.
In the —13 school year, This may be an underestimate as prior to varicella was not among the antigens for which documentation of immunization status is legally required for school attendance [ 27 , 28 ].
Second, we obtained varicella vaccine distribution and sales data from the Ontario Government Pharmacy and one manufacturer for the last full year in which Ontario had a single dose varicella program Merck, one of two manufacturers that supply varicella-containing vaccine in Ontario, provided us with data demonstrating that privately-purchased varicella vaccine now accounts for a very small proportion of their varicella vaccine sales.
While in , Viewed together, coverage estimates, vaccine distribution, and vaccine sales data imply receipt of vaccine by the targeted age group through the publicly-funded program. This supports our conclusions regarding direct and herd effects from the program.
While the methodology for determining ICU admissions has been validated [ 18 ], the diagnostic combinations used to study hospital admission for varicella-associated SSTIs varicella plus one of cellulitis, necrotizing fasciitis, or non-pharyngitis group A streptococcal infection were not.
Further, any study that relies on healthcare administrative data is subject to misclassification due to coding, or other, errors. As others have described, inferences drawn from statistical comparisons of rates between pre-policy and post-policy periods, such as ours, assume negligible impact of temporal trends [ 30 ].
We cannot rule out other factors that may have contributed to changing varicella epidemiology. The large sample size and long observation period are important strengths of our study. We used a much longer vaccine program era than previous assessment of varicella vaccine impact in Ontario and were able to demonstrate further reductions in medically-attended varicella [ 7 ].
0コメント