FAQs about the AstraZeneca vaccine

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Does the AstraZeneca vaccine have a trade name?

Not at the moment. Technically it is called ChAdOx1-nCoV19.

What is the objective of the AstraZeneca vaccine?

It is a vaccine for preventing coronavirus disease (COVID-19) in people over 18 years of age. In Spain, for the time being, it is recommended for administration in people between 18 and 55 years of age.

The vaccine does not contain SARS-CoV-2 and cannot cause COVID-19.

How does the AstraZeneca vaccine work?

The vaccine is manufactured using another virus (an adenovirus) that has been modified to transport the gene that includes the instructions for producing the S (spike) protein of the virus (the one the virus needs to be able to enter human cells).
 
When a person receives the vaccine, some of their cells read the instructions contained in this gene and produce the S-protein. Their immune system recognises this protein as being foreign, so it produces antibodies and activates T-cells (lymphocytes) to attack it. If the person later comes into contact with the SARS-CoV-2 virus, their immune system will quickly recognise it and initiate a defence response against the coronavirus.
 
The vaccine requires two doses separated by a minimum of 28 days (4 weeks) and a maximum of 84 days (12 weeks).

How effective is this vaccine?

A clinical trial has been conducted on over 24,000 participants. Half of them received the vaccine (vaccinated group) and half were given a placebo (control group, who in this case received a meningococcal vaccine).
 
Two of these studies, conducted in the United Kingdom and Brazil respectively, were evaluated by the EMA to proceed with the vaccine authorisation. The studies show a 60% reduction in the number of symptomatic cases of COVID-19 in the vaccinated group (64 cases out of 5,258 vaccinated) when compared to the control group (154 cases out of 5,210 unvaccinated).
 
Most of the participants in these studies are aged between 18 and 55 years old. There were not enough participants in the older age groups to provide data on the effectiveness of the AstraZeneca vaccine in those over 55 years of age. However, it is hoped that the vaccine will provide sufficient protection and can be administered to people aged 55 years and above.

When is immunity obtained?

21-28 days after the first dose there is already immunity. This reaches peak protection 14-21 days after the second dose.
 
Can people who have already had COVID-19 be vaccinated with the AstraZeneca vaccine?
In the clinical trial, 345 of the participants who received the vaccine had already tested positive for COVID-19. These people were excluded from the effectiveness analysis. No particular or special side effects were recorded among these 345 participants.
 
The current guidelines recommend waiting at least three months from the disease recovery date before vaccinating these people.

Can people who have already had COVID-19 be vaccinated with the AstraZeneca vaccine?

In the clinical trial, 345 of the participants who received the vaccine had already tested positive for COVID-19. These people were excluded from the effectiveness analysis. No particular or special side effects were recorded among these 345 participants.

The current guidelines recommend waiting at least three months from the disease recovery date before vaccinating these people.

Can the vaccine reduce person-to-person transmission of the virus?

We still do not know. It is not known what percentage of people who have been vaccinated may still carry the coronavirus and transmit the infection.

How long does the protection last?

We still do not know. All the trial participants will continue to be monitored (for up to 2 years) to provide further information on how long the protection lasts.

Experimental data indicates that immunity to COVID-19 is likely to last for months or years, but not for life.

Why can't children under 18 be given this vaccine?

The AstraZeneca vaccine is not recommended for children under 18 years of age because there is currently no information about the effects on this age group. The EMA has reached an agreement with AstraZeneca to conduct a trial on this population group at a later stage.

Can immunosuppressed people be given this vaccine?

The data is still limited. It is possible that immunosuppressed people will not respond as well to the vaccine, but from a safety perspective there are no additional problems.

Immunosuppressed people can be vaccinated, as they have a high risk of developing severe forms of COVID-19.

Can pregnant women be given this vaccine?

Studies using animals have not shown any adverse effects on pregnancy. However, data on the use of the AstraZeneca vaccine in pregnancy is very limited. For these reasons, vaccination is not currently recommended for pregnant women.
 
It is also recommended to avoid becoming pregnant until at least one month after the last dose of the AstraZeneca vaccine. Although there is insufficient data on vaccination and breastfeeding, there are no contraindications, for which reason, breastfeeding mothers may receive the vaccine.

What side effects may occur with this vaccine?

Most people who are vaccinated will not experience significant side effects. These may appear during the first week after vaccination. They are not usual after the first two days.
 
The frequent mild or moderate effects observed in clinical trials were (source: EMA):
 
In more than 1 out of 10 people vaccinated:

  • Pain and swelling at the injection site.
  • Tiredness.
  • Headache.
  • Muscle and/or joint pain.
  • Fever.

In less than 1 out of 10 people vaccinated:

  • Nausea and vomiting.
  • Diarrhoea.

In less than 1 out of 100 people vaccinated:

  • Loss of appetite.
  • Sweating.
  • Dizziness.
  • Abdominal pain.
  • Rash.

Painkillers, like paracetamol, can be taken, if necessary, to mitigate these effects.

What problems could be caused by a serious allergy?

The AstraZeneca vaccine is contraindicated in people who have had an anaphylactic-type hypersensitivity reaction to a previous dose of COVID-19 vaccine or one of its components.

As with all vaccines, it should always be administered under supervision and with all the medical equipment on hand to deal with a possible immediate serious allergic reaction.

Substantiated information by:

Antoni Trilla
Eduard Vieta Pascual
Josep Maria Peri
Maica Rubinat
Mariona Violan

Published: 12 March 2020
Updated: 12 March 2020

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