The only effective vaccine was (and still is) a killed virus vaccine containing inactivated particles of virulent F&M viruses.
(The only effective vaccine; was; ) (The only effective vaccine; is; a killed virus vaccine containing inactivated particles of virulent F&M viruses; T:still) (a killed virus vaccine; containing; inactivated particles of virulent F&M viruses)
The only effective vaccine The only effective vaccine a killed virus vaccine
was is containing
a killed virus vaccine containing inactivated particles of virulent F&M viruses T:still
inactivated particles of virulent F&M viruses