Vaccine reduces spread

Oxford vaccine
www.ox.ac.uk/news/2021-02-02-...
Single Dose Administration, And The Influence Of The Timing Of The Booster Dose On Immunogenicity and Efficacy Of ChAdOx1 nCoV-19 (AZD1222) Vaccine
papers.ssrn.com/sol3/papers.c...
Background
Approved for emergency use by MHRA
Two standard doses, 4 to 12 weeks
Pooled analysis of trials
Exploratory analyses, immunogenicity and efficacy of extended intervals
Priming and booster doses
Data after one dose
Methods
Phase III efficacy trials in the United Kingdom and Brazil
Phase I/II clinical trials in the UK and South Africa
Data cut-off, 7th December 2020
Over 18 years, randomised 1:1
Blinded independent endpoint review committee
Participants
N = 17,177 baseline seronegative participants
UK, n = 8,948
Brazil, n = 6,753
South Africa, n = 1,476
Infections after first dose
Positive infections, n = 619
Symptomatic infections, less than 14 days after dose, n = 332 (up by 201 from 131)
Primary analysis of overall vaccine efficacy
Including LD/SD and SD/SD groups, = 66.7% (57.4%, 74.0%)
Vaccine group
Hospitalisations = 0
Control group
Hospitalisations = 15
Hospitalisations after a single dose
Less than 22 days
2 in vaccination group, 7 in control group
More than 22 after first dose
0 in the vaccination group, 6 in the control group
Vaccine efficacy after a single standard dose
From day 22 to day 90 = 76%
Protection did not wane during this initial 3-month period
Antibody levels were maintained during this 90-day period
Minimal waning by day 90
Efficacy with a longer prime-boost interval
VE = 82.4% at 12+ weeks
Efficacy with less than 6 week, prime-boost interval
VE = 54.9%
Observations supported by immunogenicity data
Binding antibody responses more than 2-fold higher after an interval of 12 weeks or more
Compared with and interval of less than 6 weeks
(18-55 years)
Interpretation
UK single dose strategy, booster at 3 months
is an effective strategy for reducing disease,
and may be the optimal for rollout of a pandemic vaccine when supplies are limited in the short term
It is the dosing interval and not the dosing level which has a great impact on the efficacy of the vaccine
Longer prime-boost intervals done with other vaccines such as influenza, Ebola and malaria.
Professor Andrew Pollard, Chief Investigator of the Oxford Vaccine Trial
These new data provide an important verification of the interim data that was used by more than 25 regulators including the MHRA and EMA to grant the vaccine emergency use authorisation
It also supports the policy recommendation made by the Joint Committee on Vaccination and Immunisation (JCVI)
for a 12-week prime-boost interval, as they look for the optimal approach to roll out, and reassures us that people are protected from 22 days after a single dose of the vaccine
Vaccinated people less contagious
Analyses of PCR positive swabs in UK
Vaccine may have substantial reducing effect on transmission of the virus
67% reduction in positive swabs among those vaccinated