Doctors have found that some children who developed chickenpox following vaccination were unknowingly exposed to the virus before vaccination.
(Doctors; have found; that some children who developed chickenpox following vaccination were unknowingly exposed to the virus before vaccination) Context(Doctors have found,List([0, 18))):(some children who developed chickenpox following vaccination; were unknowingly exposed; to the virus; T:before vaccination)
Doctors have found,List([0, 18))
Doctors some children who developed chickenpox following vaccination
have found were unknowingly exposed
that some children who developed chickenpox following vaccination were unknowingly exposed to the virus before vaccination
to the virus T:before vaccination