Oxford AstraZeneca COVID-19 vaccine (AZD1222)
The Oxford–AstraZeneca COVID-19 vaccine, codenamed AZD1222, and sold under the brand names Covishield and Vaxzevria among others, is a viral vector vaccine for prevention of COVID-19. Developed by Oxford University and AstraZeneca, it is given by intramuscular injection, using as a vector the modified chimpanzee adenovirus ChAdOx1. The efficacy of the vaccine is 76.0% at preventing symptomatic COVID-19 beginning at 22 days following the first dose and 81.3% after the second dose. Another analysis showed that, for symptomatic COVID-19 infection after the second dose, the vaccine is 66% effective against the Alpha variant (lineage B.1.1.7), and 60% against the Delta variant (lineage B.1.617.2).
The vaccine has a good safety profile, with side effects including injection-site pain, headache, and nausea, all generally resolving within a few days. More rarely, anaphylaxis may occur (the UK Medicines and Healthcare products Regulatory Agency (MHRA) has 268 reports out of some 21.2 million vaccinations as of 14 April 2021). In very rare cases (around 1 in 100,000 people) the vaccine has been associated with an increased risk of blood clots in combination with low levels of blood platelets. According to the European Medicines Agency as of 4 April 2021, 222 cases of blood clots have been reported from the European Economic Area and the UK, where around 34 million people have received the vaccine.
On 30 December 2020, the vaccine was first approved for use in the UK vaccination programme, and the first vaccination outside of a trial was administered on 4 January 2021. The vaccine has since been approved by several medicine agencies worldwide, such as the European Medicines Agency (EMA), and the Australian Therapeutic Goods Administration, and was approved for an Emergency Use Listing by the World Health Organization (WHO). Some countries have limited its use to elderly people at higher risk for severe COVID-19 illness due to concerns over the very rare side effects of the vaccine in younger individuals.
The Oxford–AstraZeneca COVID‑19 vaccine is used to provide protection against infection by the SARS-CoV-2 virus in order to prevent COVID-19 in adults aged 18 years and older. The medicine is administered by two 0.5 ml doses injected intramuscularly into the deltoid muscle (upper arm) four to twelve weeks apart, with the WHO recommending the second is given 8 to 12 weeks after the first for optimum efficacy.
An analysis published on 19 February 2021 showed an efficacy of 76.0% at preventing symptomatic COVID-19 beginning at 22 days following the first dose, increasing to 81.3% when the second dose is given 12 weeks or more after the first. On 22 May 2021, Public Health England published an analysis showing that, for symptomatic COVID-19 infection after the second dose, the vaccine is 66% effective against the Alpha variant (lineage B.1.1.7), and 60% against the Delta variant (lineage B.1.617.2).
The most common side effects in the clinical trials were usually mild or moderate and got better within a few days after vaccination.
Vomiting, diarrhoea, swelling, redness at the injection site and low levels of blood platelets occurred in less than 1 in 10 people. Enlarged lymph nodes, decreased appetite, dizziness, sleepiness, sweating, abdominal pain, itching and rash occurred in less than 1 in 100 people.
In very rare cases (around 1 in 100,000 people) the vaccine can lead to blood clots in combination with low levels of blood platelets. The UK MHRA as of 14 April 2021 report an overall case incidence of thromboembolic events with concurrent low platelets of 7.9 per million doses (less than 1 in 100,000 people).
The Oxford–AstraZeneca COVID-19 vaccine is a replication-deficient simian adenovirus vector, containing the full‐length codon‐optimised coding sequence of SARS-CoV-2 spike protein along with a tissue plasminogen activator (tPA) leader sequence.
The Oxford–AstraZeneca COVID-19 vaccine (Vaxzevria) is a vaccine for preventing coronavirus disease 2019 (COVID-19) in people aged 18 years and older. COVID-19 is caused by SARS-CoV-2 virus. Vaxzevria is made up of another virus (of the adenovirus family) that has been modified to contain the gene for making a protein from SARS-CoV-2. Vaxzevria does not contain the virus itself and cannot cause COVID-19.
- Name: Vaxzevria (previously COVID-19 Vaccine AstraZeneca)
- Agency product number: EMEA/H/C/005675
- Active substance: ChAdOx1-SARS-COV-2
- International non-proprietary name (INN) or common name: COVID-19 Vaccine (ChAdOx1-S [recombinant])
EMA advises against use in people with history of capillary leak syndrome
EMA’s safety committee (PRAC) has concluded that people who have previously had capillary leak syndrome must not be vaccinated with Vaxzevria (formerly COVID-19 Vaccine AstraZeneca). The Committee also concluded that capillary leak syndrome should be added to the product information as a new side effect of the vaccine, together with a warning to raise awareness among healthcare professionals and patients of this risk.
Capillary leak syndrome is a very rare, serious condition that causes fluid leakage from small blood vessels (capillaries), resulting in swelling mainly in the arms and legs, low blood pressure, thickening of the blood and low blood levels of albumin (an important blood protein).
Healthcare professionals should be aware of the signs and symptoms of capillary leak syndrome and of its risk of recurrence in people who have previously been diagnosed with the condition.
People who have been vaccinated with Vaxzevria should seek immediate medical assistance if they experience rapid swelling of the arms and legs or sudden weight gain in the days following vaccination. These symptoms are often associated with feeling faint (due to low blood pressure).
The PRAC will continue to monitor for cases of the condition and will take any further actions necessary.