Week 7 - Vaccine effectiveness studies: how, why and how much? Flashcards
Define Efficacy
Protection under ideal conditions. Usually calculated from a randomized control trial
Define vaccine effectiveness
Protection expected in the real world
How do you calculate efficacy?
Efficacy= 1- Risk Ratio (ratio of attack rate among vaccinated to attack rate among unvaccinated)
How do you calculate vaccine effectiveness?
VE=1- Rate Ratio (cohort), incidence among vaccinated vs. unvaccinated
VE= 1- OR (case-control), odds of vaccination in cases vs. non-cases
Does vaccine effectiveness change?
Yes. Once there is immunity in the population there will be a change in VE
If vaccine has a relative risk of 0.6, what is the vaccine efficacy?
(1-0.6)*100= 40% efficacy (Vaccine reduced incidence by 40%)
What is a major benefit of vaccines that can be difficult to measure?
Cases averted
____________ ____________ is when a group of people experience a benefit from a different group getting vaccinated
Indirect effect
What is test negative study design?
When you swab a set of symptomatic patients and calculate VE from the proportion of positive cases (cases) to negative cases (controls)
What are two things to keep in mind when deciding vaccine recommendations?
Which age groups would benefit the most from the vaccine and how many doses should be given?