On February 5, 2021 the WHO’s released their interim position paper and stated “there are still critical unknowns regarding the efficacy of vaccination in reducing transmission”, and that “people who are vaccinated should not be exempt from complying with other travel risk-reduction measures.” [1]
Current “scientific unknowns… concerning the effectiveness of COVID-19 vaccines”:
- efficacy in preventing disease
- ability of limiting transmission including for new variants
- duration of protection
- timing of booster doses
- whether vaccination offers protection against asymptomatic infection
- age and population groups that should be prioritized for vaccination
- how long before travel vaccines should be offered
- possible exemption of people who have antibodies against SARS-CoV-2
For vaccines that were sold as 95% effective (Pfizer), 94.1% effective (Moderna), 2 doses 90% effective (AstraZeneca) – But what does “effective” mean?