From the http://www.cfhi-fcass.ca/sf-docs/default-source/reports/risk-analytica.pdf figure 4 p23, 45 out 100 girls in the age group make an ED visit per year. Here we have 1/10 in 42 days, which is a rate of 87 per year, nearly twice as much.
Using the normal background rate of .45/year, we would have expected about .45*195,270*42/365 = 10,111 ED visits, but 19,351 were observed. That's an excess of 9,240 ED visits.
The standard deviation for this number of people can be computed as sqrt(Np(1-p)) for p the probability of making an ED visit in the background, in this case .45*42/365. It is 98. That means the number of ED visits observed was about 9240/98 = 94 standard deviations in excess of the expected. In other words, the event was highly highly significant and the vaccine most likely causally connected unless there is some other systematic bias.