But her thinking changed when three similar cases occurred during the next two years.
No more than two new cases have occurred on any day since May 21, he said.
However, cases can occur at any time during the year.
Officials said they were not certain how the other case occurred.
Almost all cases occur by the age of 5 months.
These cases occurred in the period from 1999 to 2006.
But now half the reported cases occur in children 10 and older.
Most cases occur within 6 months of taking this drug.
This case has only occurred five times, with the most recent such decision being from 2012.
After this, several cases occurred in the rest of the country.