Vaccine reduces spread

Oxford vaccine

Single Dose Administration, And The Influence Of The Timing Of The Booster Dose On Immunogenicity and Efficacy Of ChAdOx1 nCoV-19 (AZD1222) Vaccine

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