Ro = 1/S. What does this mean
Inverse relationship between basic reproduction number and proportion of population susceptible to disease
(Ro = basic reproduction number)
S = 1 -q . What does this mean?
i.e. Immune + susceptible = 1
q = the herd immunity level
What parameters must be met for the condition to die out?
q > 1 - (1/Ro)
Describe Phase 1 trials vaccines.
- Primarily for safety, also assesses immunogenicity
- small number of adults
Phase 2 trials vaccines
- Primarily assesses immune response but also expands safety database
- includes all group likely to use vaccine
Phase 3 trials vaccines
- Protection studies, usually placebo controlled double blind trials
- requires good disease surveillance
In which stage is vaccine efficacy determined?
Phase 3 trials.
Equation for vaccine efficacy.
Vaccine efficacy = 1 - (Attack rate in vaccinated/attack rate in unvaccinated)
Equation for herd effect
Herd effect = 1 - (attack rate unvaccinated post introduction/attack rate unvaccinated pre introduction)
What are the 3 components of vaccines?
- Antigen
- Adjuvant
- Excipients