Immunogenicity, Efficacy and Safety Trial of the Convacell Vaccine in Healthy Volunteers Aged 18 Years and Older

The trial will be conducted in two stages (Stage IIb and Stage III). • Stage IIb Participants will be vaccinated one dose or two doses of the Convacell vaccine. Investigators will compare one dose and two doses groups and will choose the best vaccine dosage regimen in terms of immunogenicity and safety. • Stage III Participants will be vaccinated the Convacell vaccine or Placebo. Investigators will use the dosage regimen chosen in IIb stage.