AstraZeneca's (www.AstraZeneca.com) COVID-19 vaccine has been granted approval in the European Union (EU) by the European Medicine Agency (EMA) as a third dose booster in adults.

Healthcare professionals can now use AstraZeneca COVID-19 vaccine as a third dose booster in patients previously given a primary vaccine schedule of either AstraZeneca COVID-19 vaccine or an EU-approved mRNA COVID-19 vaccine.

The authorisation is based on a review by the Committee for Medicinal Products for Human Use (CHMP) of the substantial body of evidence demonstrating an increased immune response after a third dose booster with AstraZeneca COVID-19 vaccine following a primary vaccine schedule of either AstraZeneca COVID-19 vaccine or an mRNA COVID-19 vaccine. [1-5]

Although more than 65% of the global population has received at least one dose of a COVID-19 vaccine [6], there remains a significant challenge to ensure people receive both their primary vaccine schedule and third dose booster, and healthcare professionals now have greater flexibility in their choice of vaccine.

Mene Pangalos, Executive Vice President, BioPharmaceuticals R&D, AstraZeneca said: “Today’s marketing authorisation for AstraZeneca’s COVID-19 vaccine as a third dose booster is an important step towards our goal of providing continued protection against COVID-19 for all populations. Ensuring a longer duration of immune protection is essential to the long-term management of COVID-19 globally, and boosters can address the waning of protection over time that has been seen with all primary vaccine schedules to date.”

There is a substantial body of evidence supporting AstraZeneca COVID-19 vaccine as a third dose booster following all primary vaccination schedules tested to date including AstraZeneca COVID-19 vaccine, mRNA vaccines, and CoronaVac [1,7-12].      

AstraZeneca COVID-19 vaccine is already authorised as a homologous booster (patients previously given a primary vaccine schedule of AstraZeneca COVID-19 vaccine) in the UK, and several countries in Asia and Latin America. It has also been authorised as a heterologous booster (patients previously given a primary vaccine schedule of either a viral vector vaccine other than AstraZeneca COVID-19 vaccine or an inactivated vaccine or an mRNA COVID-19 vaccine) in a number of non-EU countries.

AstraZeneca COVID-19 vaccine is estimated to have helped prevent 50 million COVID-19 cases, five million hospitalisations, and saved more than one million lives worldwide, based on model outcomes assessing COVID-19 worldwide [13].

AstraZeneca COVID-19 vaccine (ChAdOx1-S [Recombinant], formerly AZD1222)

AstraZeneca COVID-19 vaccine was invented by the University of Oxford. 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.

AstraZeneca COVID-19 vaccine is a ‘viral vector’ vaccine, which means a version of a virus that cannot cause disease is used as part of the vaccine, leaving the body knowing how to fight it if it is exposed to the real virus later. This vaccine technology has been used by scientists over the past 40 years to fight other infectious diseases such as the flu, Ebola, and HIV [14].

The vaccine has been granted a conditional marketing authorisation or emergency use in more than 125 countries. It also has Emergency Use Listing from the World Health Organization, which accelerates the pathway to access in up to 144 countries through the COVAX Facility.

Under a sub-license agreement with AstraZeneca, the vaccine is manufactured and supplied by the Serum Institute of India under the name COVISHIELD.

References:

1. Maheshi N Ramasamy et al. Immunogenicity and safety of AZD1222 (ChAdOx1 nCoV-19) and AZD2816 as third-dose boosters in adults previously vaccinated with AZD1222 or an mRNA vaccine. Presented at the European Society of Clinical Microbiology and Infectious Diseases Congress (ECCMID), Lisbon, 2022.
2. Flaxman A, et al. Reactogenicity and immunogenicity after a late second dose or a third dose of ChAdOx1 nCoV-19 (AZD1222) in the UK: a substudy of two randomized controlled trials (COV001 and COV002). The Lancet. Available at: https://bit.ly/3lUSEhT. Accessed May 2022.
3. Munro A PS, et al. Safety and immunogenicity of seven COVID-19 vaccines as a third dose (booster) following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK (COV-BOOST): a blinded, multicentre, randomised, controlled, phase 2 trial. The Lancet. Available at: https://bit.ly/3sS43Tq. Accessed May 2022. 
4. Participants were adults 18 years-old and older who would benefit from prevention with Evusheld, defined as having increased risk for inadequate response to active immunisation (predicted poor responders to vaccines or intolerant to vaccination) or having increased risk Liu X et al. Safety and immunogenicity of heterologous versus homologous prime-boost schedules with an adenoviral vectored and mRNA COVID-19 vaccine (Com-COV): a single-blind, randomised, non-inferiority trial. Available at: https://bit.ly/3NvsaPI. Accessed May 2022.
5. Dejnirattisai W et al. SARS-CoV-2 Omicron-B.1.1.529 leads to widespread escape from neutralizing antibody responses. Available at:  https://bit.ly/3LA5oVm. Accessed May 2022.
6. Ritchie et al. Coronavirus (COVID-19) Vaccinations - Our World in Data. Accessed at: https://bit.ly/38FL73t. Accessed May 2022
7. Flaxman A, et al. Reactogenicity and immunogenicity after a late second dose or a third dose of ChAdOx1 nCoV-19 (AZD1222) in the UK: a substudy of two randomized controlled trials (COV001 and COV002). The Lancet. Available at: https://bit.ly/39N3Hqe. Accessed May 2022.
8. Munro A PS, et al. Safety and immunogenicity of seven COVID-19 vaccines as a third dose (booster) following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK (COV-BOOST): a blinded, multicentre, randomised, controlled, phase 2 trial. The Lancet. Available at:
9. https://bit.ly/3yWlgii. Accessed May 2022.
10. Jara A et al. Effectiveness of Homologous and Heterologous Booster Shots for an Inactivated SARS-CoV-2 Vaccine: A Large-Scale Observational Study. Available at SSRN: https://bit.ly/39NmlP4. Accessed May 2022.
11. Vargas L et al. Serological study of CoronaVac vaccine and booster doses in Chile: immunogenicity and persistence of anti-SARS-CoV-2 S antibodies. Pre-print available at: https://bit.ly/38aPTpa. Accessed May 2022.
12. Costa Clemens SA, et al. Heterologous versus homologous COVID-19 booster vaccination in previous recipients of two doses of CoronaVac COVID-19 vaccine in Brazil (RHH-001): a phase 4, non-inferiority, single blind randomised study. Available at: https://bit.ly/3sV3k3U. Accessed May 2022.
13. Data estimates based on model outcomes with transmission defined as 200 infections per 100,000 people per day. AZD1222 lives and hospitalisations prevented data on file. Data on File Number: REF-131228, 10 November 2021. AstraZeneca UK Ltd.
14. Zhang et al. Adenoviral vector-based strategies against infectious disease and cancer. Available at: https://bit.ly/3act3hz. Accessed May 2022