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The COVID Astra Zeneca / Oxford Vaccine

We are offering the Astra Zeneca vaccine to our clinically extremely vulnerable patients to avoid you having to spend extra time at the centre as it does not require you to wait at the centre after having the vaccination. If you prefer to have the Pfizer vaccination you opt for this, please be aware you will need to be observed in the observation room for 15 mins after having the vaccine.

How does the Asrra Zeneca Vaccine work?

COVID-19 Vaccine AstraZeneca is a non-replicating viral vector vaccine which uses part of a weakened adenovirus as a carrier to deliver the genetic sequence for the SARS-CoV-2 virus spike protein into cells. The adenovirus has been modified so that it cannot replicate (grow and multiply by making copies of itself) in human cells and therefore cannot cause any disease.

The genes that encode for the spike protein on the SARS-CoV-2 virus have been inserted into the adenovirus’s genetic code to make the vaccine. When the vaccine is injected, it enters the host’s cells which then manufacture the spike protein. This then stimulates the immune system which reacts by producing antibodies and activating memory T cells to the SARS-CoV-2 virus without causing disease.

How was the vaccine trialled?

The safety and immunogenicity of the COVID-19 Vaccine AstraZeneca has been evaluated from clinical trials which began in April 2020 and included just under 24,000 participants (at the time of analysis) aged 18 years and over from diverse geographical and racial groups in the UK, Brazil and South Africa. The participants were randomised to receive either COVID-19 Vaccine AstraZeneca or a control (meningococcal vaccine or saline).

Trials are also being conducted in the United States, Kenya, Japan and India.

How effective is the Astra Zeneca Vaccine?

Following vaccination with COVID-19 Vaccine AstraZeneca, trial participants in all age groups made high levels of both neutralising and spike protein-binding antibodies after the first vaccination and levels of these increased after a second dose. Spike-specific T cell responses were also shown to be induced after a single immunisation and were maintained after the second dose (Fig 1). Leaving a longer interval between the two doses has been shown to increase the immune response.

Trial data showed evidence of very high protection against severe disease and hospitalisation. It also showed that participants who had one or more comorbidities(read a full definition of this term) had an immune response and vaccine efficacy similar to that observed in the overall study population.

In an analysis of over 11,000 patients in the phase 3 study, overall vaccine efficacy against symptomatic disease was 70.4%.

Is the vaccine safe?

The side-effects seen in clinical trial recipients following vaccination with COVID-19 Vaccine AstraZeneca were mild to moderate and usually self-resolving within a few days of vaccination. Local reactions, such as redness, swelling, warmth, itching, pain and tenderness at the injection site were commonly reported after vaccination.

Systemic reactions (reactions affecting the whole body) such as tiredness, headache, fever, nausea, chills, muscle aches and joint pain were also reported. These are all reactions commonly seen after other vaccinations such as flu vaccine.

When compared with the first dose, adverse reactions reported after the second dose were milder and reported less frequently. Adverse reactions were also generally milder and reported less frequently in older adults (≥65 years old).

In the phase 3 study, only 1 serious adverse event was reported as possibly linked to the study vaccine. This was a case of transverse myelitis which occurred 14 days after dose 2.

What are the components of the Astra Zeneca vaccine?

In addition to the recombinant, replication-deficient chimpanzee adenovirus vector encoding the SARS-CoV-2 Spike (S) glycoprotein, the vaccine also contains:

L-Histidine
L-Histidine hydrochloride monohydrate
Magnesium chloride hexahydrate
Polysorbate 80
Ethanol
Sucrose
Sodium chloride
Disodium edetate dihydrate
Water for injections

Can you have the Astra Zeneca Vaccine if you are pregnant?

Although the available data do not indicate any safety concern or harm to pregnancy, there is insufficient evidence to recommend the routine use of COVID-19 vaccine during pregnancy.

However, the JCVI has advised that, for women who are offered COVID-19 vaccine, vaccination in pregnancy should be considered where the risk of exposure to SARS-CoV-2 infection is high and cannot be avoided, or where the woman has underlying conditions that put them at very high risk of serious complications of COVID-19. In these circumstances, clinicians should discuss the risks and benefits of vaccination with the woman, who should be told about the absence of safety data for the vaccine in pregnancy.

JCVI does not advise routine pregnancy testing before receipt of a COVID-19 vaccine. Those who are trying to become pregnant do not need to avoid pregnancy after vaccination.

If a woman finds out she is pregnant after she has started a course of COVID-19 vaccine, she should complete her pregnancy before finishing the recommended schedule. Women should be offered vaccine as soon as possible after pregnancy.

Termination of pregnancy following inadvertent immunisation should not be recommended. Surveillance of inadvertent administration in pregnancy is being conducted for the UK by the PHE Immunisation Department – if a pregnant woman is inadvertently given COVID-19 vaccine, this should be reported to PHE (https://www.gov.uk/guidance/vaccination-in-pregnancy-vip).

Can you have the Astra Zeneca vaccine if you are breastfeeding?

There is no known risk associated with giving non-live vaccines whilst breastfeeding. JCVI advises that breastfeeding women may be offered vaccination with the COVID-19 Vaccine AstraZeneca.

The developmental and health benefits of breastfeeding should be considered along with the woman’s clinical need for immunisation against COVID-19, and the woman should be informed about the absence of safety data for the vaccine in breastfeeding women.

Can I have the Astra Zeneca Vaccine as second dose if I reacted to Pfizer first dose?

There is no evidence as to the interchangeability of different COVID-19 vaccines although studies are underway. For this reason, it is currently recommended that the same COVID-19 vaccine product is given for both doses.

For individuals who started the schedule and who attend for vaccination at a site where the same vaccine is not available, or if the first product received is unknown, it is reasonable to offer a single dose of the locally available product to complete the schedule. This option is preferred if that individual is likely to be at immediate high risk or is considered unlikely to attend again. In these circumstances, as both the AstraZeneca and Pfizer-BioNTech vaccines are based on the spike protein, it is likely that the second dose will help to boost the response to the first dose. For this reason, until additional information becomes available, further doses are not required.

There should be a minimum interval of 28 days between doses of COVID-19 Vaccine AstraZeneca. It is recommended that the second dose should be administered between 4 and 12 weeks after the first dose or in accordance with official guidance at the time.

If an interval longer than the recommended interval is left between doses, the second dose should still be given (preferably using the same vaccine as was given for the first dose if possible). The course does not need to be restarted.

If the second dose of the COVID-19 Vaccine AstraZeneca is given at less than the recommended minimum 28-day interval, but at least 21 days after the first dose, it does not need to be repeated. If the second dose is given less than 21 days after the first, it should be discounted and another dose (a third dose) should be given at least 28 days after the dose given too early.

 

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