New research from Public Health Ontario (PHO) has shown that the introduction of the chickenpox vaccination program for children in Ontario was associated with a 71 per cent decrease in doctor's office and emergency room visits and a 59 per cent decrease in hospitalizations for this disease.
Chickenpox is a common childhood illness with the potential for serious complications, even among healthy children.
In a new paper being published in PLOS One titled “Twenty years of medically-attended pediatric varicella and herpes zoster in Ontario, Canada: a population-based study,” Anne Wormsbecker worked with PHO colleagues to examine data on chickenpox and shingles from the past 20 years.
The study compared the number of Ontario doctor office visits, emergency department (ED) visits and intensive care unit (ICU) admissions for children aged 18 and younger over three time periods – pre-vaccine period (1992-1998), privately available vaccine (1999-2003) and the public vaccination program (2004-2011).
Wormsbecker is a medical epidemiologist at PHO, a pediatrician in Toronto and the lead researcher on the study.
"With this large, population-based study, we have shown that medically-attended chickenpox decreased significantly during the 20-year study period, particularly since the varicella vaccine became publicly funded in Ontario," said Wormsbecker in a news release.
"The results also suggest a 'herd immunity' effect, as we saw decreases in chickenpox incidence in both age groups who were eligible to receive the vaccine, as well as older age groups, who would not have been eligible for vaccine. These older groups are benefiting indirectly from the vaccination program; those susceptible to chickenpox are not getting ill because less of the virus is circulating in the community, resulting in less opportunity to become ill from this infectious disease."
Between 1992 and 2011 (2010 for emergency department visits), Wormsbecker and PHO colleagues observed 600,208 physician office visits, 55,472 ED visits, and 2,701 hospitalizations for chickenpox among Ontario children.
They found that the incidence of office visits due to chickenpox declined from a high of 25.1/1,000 in 1994 (pre-vaccine availability) to a low of 3.2/1,000 in 2011 (publicly funded vaccine program).
Emergency department visits and hospitalizations followed similar patterns of decreasing rates later in the study period.
Doctor office visits for chickenpox saw significant year-over-year decreases for all groups of children aged 18 and younger.
As well, chickenpox-associated skin and soft tissue infections declined significantly in children younger than 12, and rates of ICU admissions decreased significantly for children younger than one year of age over the study period.
For children five- to 17-years-old, shingles office visits decreased while ED visits increased. There was also a small, non-significant decrease in hospitalizations.
"Applied immunization research is a priority for PHO. This research is an example of PHO's work in evaluating immunization programs and their effectiveness in preventing disease and promoting health in Ontario," said Shelley Deeks, medical director of immunization and vaccine-preventable disease at PHO and senior author on the paper.
