"Vaccine Season" by Hannu Rajaniemi

In a post-pandemic future where scientists have made great strides in eliminating disease, a young boy faces his fears and ventures out to his grandfather's island to give him an important vaccine.

This story appears in the anthology Make Shift: Dispatches from the Post-Pandemic Future, edited by Gideon Lichfield and available for pre-order from The MIT Press.
Content advisory: Discussion of pandemics, near-drowning