The trial will recruit approximately 2,250 participants across UK, South Africa, Brazil and Poland. This includes 86 participants who have been recruited from across the Lothians at the Western General Hospital, with CIRGs Dr Matthew Adam as the local Principal Investigator.

AZD2816 will be administered to individuals who have previously been fully vaccinated with two doses of Vaxzevria or an mRNA vaccine, at least three months after their last injection. In non-vaccinated individuals, AZD2816 will be given as two doses, four or twelve weeks apart, or given as a second dose following a first dose of Vaxzevria four weeks apart.

AZD2816 has been designed using the same adenoviral vector platform as Vaxzevria, with minor genetic alterations to the spike protein based on the Beta (B.1.351, South African) variant.

Sir Mene Pangalos, Executive Vice President, BioPharmaceuticals R&D, said: “It is important we continue to stay ahead of genetically distinct variants of the coronavirus. AZD2816 should help broaden individuals immune response against emerging variants of concern. Initiating the Phase II/III trial for AZD2816 means we can be prepared should a variant vaccine be required in the future.”

“Testing booster doses of existing vaccines and new variant vaccines is important to ensure we are best prepared to stay ahead of the coronavirus pandemic, should their use be needed.” Professor Sir Andrew J Pollard, chief investigator and director of the Oxford Vaccine Group at the University of Oxford

Initial data from the trial is expected later this year and, once available, will be submitted to regulators for assessment as a next-generation booster vaccine and through an expedited regulatory pathway.

D7220C00001 is a Phase II/III partially double-blinded, randomised, multinational, active-controlled trial in both previously vaccinated and unvaccinated adults to determine the safety and immunogenicity of AZD2816, a vaccine for the prevention of COVID-19 caused by variant strains of the SARS-CoV-2 virus.

Trial participants aged 18 years or over who are SARS-CoV-2 nucleocapsid seronegative will be randomised to minimise group differences in terms of age, gender and the presence of comorbidities. Participants will receive intramuscular administration of either Vaxzevria (5 ×1010 viral particles) or AZD2816 (5 ×1010 viral particles). In addition, seropositive participants will be enrolled, with a cap of 10% of the seronegative population, to support exploratory analysis.

AZD2816 has been built using the same adenoviral vector platform as with Vaxzevria, with minor genetic alterations to the spike protein based on the Beta (B.1.351, South African) variant. The Beta variant vaccine contains ten changes across the spike protein, many of which are also seen in other variants of concern, and which lead to effects such as, reduced ability of antibodies induced against the original virus to block cell entry (K417N, E484K, N501Y); increased infectivity compared to the original virus (D614G); reduced sensitivity of neutralising antibodies to the original virus (L452R). These modifications are only minor and in all other ways the two vaccines are the same.

Vaxzevria, formally AZD1222
Vaxzevria was co-invented by the University of Oxford and its spin-out company, Vaccitech. It uses a replication-deficient chimpanzee viral vector based on a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees and contains the genetic material of the SARS-CoV-2 virus spike protein. After vaccination, the surface spike protein is produced, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body.

The vaccine has been granted a conditional marketing authorisation or emergency use in more than 80 countries across six continents. More than 600 million doses of COVID-19 Vaccine AstraZeneca have been supplied to 170 countries worldwide, including more than 100 countries through the COVAX Facility. In the UK, Vaxzevria is known as COVID-19 Vaccine AstraZeneca.