Week 7 - Vaccine effectiveness studies: how, why and how much?

Question 1

Define Efficacy

Answer 1

Protection under ideal conditions. Usually calculated from a randomized control trial

Question 2

Define vaccine effectiveness

Answer 2

Protection expected in the real world

Question 3

How do you calculate efficacy?

Answer 3

Efficacy= 1- Risk Ratio (ratio of attack rate among vaccinated to attack rate among unvaccinated)

Question 4

How do you calculate vaccine effectiveness?

Answer 4

VE=1- Rate Ratio (cohort), incidence among vaccinated vs. unvaccinated
VE= 1- OR (case-control), odds of vaccination in cases vs. non-cases

Question 5

Does vaccine effectiveness change?

Answer 5

Yes. Once there is immunity in the population there will be a change in VE

Question 6

If vaccine has a relative risk of 0.6, what is the vaccine efficacy?

Answer 6

(1-0.6)*100= 40% efficacy (Vaccine reduced incidence by 40%)

Question 7

What is a major benefit of vaccines that can be difficult to measure?

Answer 7

Cases averted

Question 8

____________ ____________ is when a group of people experience a benefit from a different group getting vaccinated

Answer 8

Indirect effect

Question 9

What is test negative study design?

Answer 9

When you swab a set of symptomatic patients and calculate VE from the proportion of positive cases (cases) to negative cases (controls)

Question 10

What are two things to keep in mind when deciding vaccine recommendations?

Answer 10

Which age groups would benefit the most from the vaccine and how many doses should be given?