March 25, 2015|Categories: Analytics and Research
This past winter, the U.S. experienced an unusually intense measles season. As of March 20, 2015, there have been 178 reported cases of measles in the U.S., compared with an average of 61 cases per year between 2001 and 2011. Although the largest outbreak originated at Disneyland in Southern California and spread throughout the West, there have also been independent outbreaks affecting states throughout the country. The two states most afflicted by outbreaks this season were California and Illinois, with 120 and 15 cases respectively. All other states have had no more than nine confirmed cases.
Considering the public’s focus on measles this season, we used data from athenahealth’s cloud-based electronic health record (EHR) service to determine if we could detect an uptick in vaccination rates for children cared for by pediatricians and family practitioners around the country.
Measles Vaccination Landscape
Current standards call for children to be vaccinated once between 12 and15 months of age, and again between ages 4 and 6. For our analysis, we looked at vaccination rates for all children from newborn-- to age 6. With this approach, we would include children in the target age groups, as well as children whose parents decided not to vaccinate them during the recommended timeframe but then reconsidered given the publicity around measles.
Measles, mumps and rubella (MMR) vaccinations are often correlated with school schedules, so we defined “seasons” stretching from July of one year to June of the following year. These seasons are central to our definition of vaccination rate for a given week: it is the proportion of all patients seen so far that season who received a vaccination.
We compared vaccination rates over the last three seasons, and the results of our analysis on the national level appear in Figure 1. We looked at 19 million patient visits to 14,000 providers, mainly pediatricians and family practitioners, all of whom have been in our database since before July 1, 2012.
The data does not suggest that vaccination rates have increased substantially on a national scale to date. 13.4% of children in the target age range have received vaccinations from July 1, 2014 to March 14, 2015, compared with 13.2% over the same time period in 2013-2014 and 13.3% during the 2012–2013 season.
The data in Illinois and California, however, show an increase in vaccination activity during the last eight weeks.
As indicated in Figure 2, this season’s vaccination rates in those two states were similar to previous seasons, up until the middle of January, when the measles outbreak in California began to garner increased media attention. In the weeks that followed, however, the gap between vaccination rates in the current season and the 2013-2014 season widened. For both states, over the last seven weeks, the difference in vaccination rates is statistically significant, indicating that rates begun to differ from previous seasons. Thus, parents’ fears of their children suffering a measles infection appear to have made them more likely to get their kids vaccinated.
As of this writing, the California measles outbreak appears to have subsided, with only three new cases reported in the first two weeks of March. We will continue to monitor vaccination behaviors and report back if we observe interesting developments.