Because the wording didn't specify Primary or Secondary response, those who thought 'Primary' were correct that IgM was the same isotype for both routes. Risk of a mutated, more deadly form escaping the repository labs. The ultimate triumph of human-kind over a deadly disease. It may be a useful vector for development of vaccines to other viruses. If smallpox does exist somewhere in the world, these stocks would be useful in creating a vaccine.
Human beings have no right to purposely destroy a species.