FAQs about COVID-19 vaccines




This page aims to answer common questions about COVID-19 vaccines:

The Oxford-AstraZeneca Vaccine – ChAdOx1 nCoV-19

If you would like to suggest questions to be included on this page, please use our feedback form.


How can I get the COVID-19 vaccine?

For information about who is eligible to receive the vaccine in the UK, see COVID-19 vaccines. You will be contacted by the NHS if you are eligible to receive the vaccine. Information about who is eligible to receive the vaccine in the USA is available from the Centers for Disease Control and Prevention.

COVID-19 vaccination strategies for the EU/EEA is available from the European Centre for Disease Control and Prevention.


How will the vaccine ‘feel’ when I receive it?

Both the Pfizer-BioNTech and Oxford-AstraZeneca vaccine are given as a two-dose course. They are given as an injection into the upper arm, similar to other vaccines you receive as an adult. Most people feel a slight sting and a sensation of pressure when the vaccine is being given.  The vaccine won’t feel cold.


Will I get side effects from the vaccine?

The Pfizer-BioNTech and Oxford-AstraZeneca vaccines have a similar safety profile to other vaccines. Side effects that would be expected are mostly “flu-like” symptoms such as a headache, aching, fever, as well as pain and tenderness at the injection site. More information about expected side effects and allergic reactions is available here.


Can I take multiple different types of vaccine, as an insurance policy? 

Most of the vaccines developed so far work in similar ways, by making responses against a spike protein. This means vaccinating with different versions is not necessary, but studies are needed to see if boosters with different vaccines might work well. There is every reason to believe that this would work but does need to be formally tested.


Should I get the COVID-19 vaccine if I’ve already had COVID-19?

If you are in a priority group to receive the vaccine, it is recommended that you have it, even if you have already had COVID-19. There is increasing evidence to show that natural infection with COVID-19 does not lead to long-lasting immunity. 


How long will I be protected from the virus with these vaccines? 

At this point we cannot say, but other vaccines using the Oxford ChAdOx1 technology are proven to provide immune responses that can persist for a year or more. 


Can life go back to normal now? 

Vaccines are one tool for combating the virus, but we need multiple vaccines to be successful. These will only be effective if they are used by people around the world, in combination with other public health measures and effective treatments for those who still become ill with COVID-19.


Will I still need to follow social distancing rules and wear a mask after having the vaccine?

A vaccine is one of many tools needed to control the pandemic. We will need to follow public health measures until the rate of virus transmission is much lower. We don’t yet know whether the vaccine prevents transmission of the virus, and this is something researchers are still looking into. Some people in our communities are not able to receive the vaccine yet. It is important that we continue with the infection control measures to protect everyone in our communities.


How much will the COVID-19 vaccines cost? 

Those who are eligible to receive a COVID-19 vaccine as part of the UK COVID-19 vaccination programme will be entitled to a free vaccine on the NHS. 

As part of an agreement between the University of Oxford and AstraZeneca, the ChAdOx1 nCoV-19 vaccine will be supplied on a not-for-profit basis for the duration of the pandemic and in perpetuity for low- and middle-income countries.


Can you guarantee that no-one will fall seriously ill or even die by taking the COVID-19 vaccines? 

There are risks associated with any medicine, and the COVID-19 vaccine trials have not indicated that these vaccines lead to any unexpected reactions. Both licensed vaccines have a similar safety profile to other vaccines.

In any large trial of a new medicine, incidents are followed up rigorously with an independent group of safety experts. The research teams have collected large safety databases during their trials, and these were submitted to regulators for review. Trial volunteers are still being followed for any longer-term effects. 


Can I get COVID-19 from these vaccines? 

None of the currently approved vaccines are using a live SARS-CoV-2 virus in them; so you cannot get COVID-19 from them. It is common to get symptoms that feel the same as an infection for a few days after you have a vaccine (e.g. feeling “fluey”).  This is a sign that your immune system is responding to the vaccine, not that you have got a real infection. 


These vaccines have been developed so quickly; how do I know that they have been tested properly? 

The COVID-19 pandemic led to an international effort in vaccine development. The urgent need to control the pandemic, and save lives, meant that development processes were significantly accelerated. This does not mean that steps were skipped, or that safety was compromised. 

More information about the speed of vaccine development is available here: Vaccines 101: How new vaccines are developed


Are the COVID-19 vaccines safe?   

The COVID-19 vaccines currently approved have been thoroughly reviewed by the Medicines and Healthcare products Regulatory Agency (the MHRA). The regulatory team have completed a full review of the safety information reported from the trials, which includes several months follow-up data from 23,000 people for the Oxford-AstraZeneca vaccine and 44,000 people for the Pfizer-BioNTech vaccine. 


What does safe mean? 

What this means, is that the MHRA has reviewed all the information from the clinical trials of these vaccines. This would include reviewing all the side effects and medical conditions that people in the trials experienced.   

The number of illnesses reported in the vaccinated group is compared with the control group to see whether the vaccine could be associated with an increase in any medical conditions. The rates of illness are also compared with the rate of those illnesses in the general population. For any severe illnesses reported, a specialist doctor involved in treating the person and an independent safety committee consider whether the illness could be associated to the vaccine. 

All the information about adverse events (unexpected illnesses) reported during the trial has been provided to the regulators, and the safety profile of both the Oxford-AstraZeneca and the Pfizer BioNTech vaccines is similar to that of other vaccines. 


Can these genetic vaccines alter my DNA?

There has been inaccurate information circulating online about the new technologies used for the Pfizer-BioNTech and Oxford-AstraZeneca vaccines. Whilst these technologies both use genetic codes to produce the spike protein inside the body, this code cannot be incorporated into the body’s DNA. This is because:

  • mRNA vaccines like the Pfizer/BioNTech vaccine cannot reach the part of the cell that holds the DNA, called the nucleus.
  • mRNA cannot be translated back into DNA.
  • Both mRNA and adenovirus vaccines do not contain the “specialised tools” needed to “copy” or “edit” DNA.

These vaccines cannot replicate inside the body and only stay in the body for a few days. After helping the cells to produce an immune response against the spike protein, the vaccine is removed by the body.

For more information about the genetic technologies used in the COVID-19 vaccines, please see COVID-19 vaccines.


Do the COVID-19 vaccines contain human or animal products?

The Pfizer-BioNTech and Oxford-AstraZeneca vaccines do not contain any human or animal derived ingredients.


Do the COVID-19 vaccines contain human foetal cells?

The manufacturing process for the Oxford-AstraZeneca vaccine involves the production of a virus, the adenovirus, which carries the genetic material to the cells inside the body. To produce this virus in the laboratory, a “host” cell line is needed. For some vaccines, chicken cells are used for this process, and for other human cell lines are used to produce the virus. The Oxford-AstraZeneca vaccine uses a cell line called HEK-293 cells. 

HEK-293 is the name given to a specific line of cells used in various scientific applications. The original cells were taken from the kidney of a legally aborted foetus in 1973. HEK-293 cells used nowadays are clones of those original cells, but are not themselves the cells of the aborted foetus.

See also, information about the use of human cell lines in the production of vaccines.


What if the coronavirus mutates: will the vaccine still work?

The currently available COVID-19 vaccines protect people from SARS-CoV-2 infection in two ways. The first is by triggering the immune system to produce antibodies against the spike protein which is found on the surface of SARS-CoV-2, and they also stimulate another part of the immune system (T-cells) to help fight infection.  

It is possible that the SARS-CoV-2 virus could mutate its spike protein (the “key” that allows it to get into human cells) in such a way that our antibodies wouldn’t be able to stick to it, and our T-cells wouldn’t be able to “see” it. 

But a change like this could also have a big downside for the virus, because it could make it much more difficult for it to stick to and infect human cells. This might mean that viruses carrying this mutation would naturally die out, as they would be out-competed by viruses with “normal” spike protein.

At the moment, we don’t have enough evidence to suggest that the mutations in the SARS-CoV-2 virus are significant enough to affect the way that vaccines or treatments work.

In the worst-case scenario where a spike has changed so much that no antibodies or T cells work against it, we would have to produce a new vaccine against the new spike protein. But, scientists are closely monitoring any changes to the virus so that we can predict whether an alternative vaccine might be needed. A benefit of the new types of vaccines (mRNA and adenoviral vectors) is that it is relatively quick and easy to change the genetic code so that it incorporates these mutations, if this was necessary.

Can COVID-19 vaccines affect fertility?

There is no evidence that the immune response to coronaviruses has any impact on fertility in animals or humans, and there is no biological mechanism that has been shown to result in an impact on fertility. Regulators have looked at the data carefully from the clinical trials and have not recommended any precautions for individuals planning to become pregnant. 


After having the vaccine, will I have a positive result from an antibody test?

The COVID-19 vaccines currently in use target the spike (S) protein of the coronavirus to produce an immune response. Antibody tests used to check for a previous COVID-19 infection have been designed to assess the presence of antibodies against one or other of two different proteins from the coronavirus: the spike (S) protein and the nucleocapsid (N) protein. After vaccination, presence of antibodies against the S protein is expected, producing a positive result. However, the presence of antibodies against the N protein would not be expected, so for this type of antibody test, a negative result would be seen following vaccination. Vaccinated individuals who have had an N protein antibody test that is negative do not need additional vaccine doses above those recommended, as the results of this test are not affected by vaccination. Both tests would be expected to show a positive result after a recent COVID-19 infection.


The Oxford-AstraZeneca Vaccine – ChAdOx1 nCoV-19

How does the Oxford-AstraZeneca vaccine work?  

ChAdOx1 nCoV-19 is made from a virus (ChAdOx1), which is a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees. The adenovirus has been genetically changed so that it is impossible for it to cause infection in humans.   

Genetic material has been added to the ChAdOx1 construct, that is used to make proteins from the COVID-19 coronavirus (SARS-CoV-2) called Spike glycoprotein (S). This protein is found on the surface of SARS-CoV-2 and plays an essential role in the infection pathway of the SARS-CoV-2 virus.

Vaccinating with ChAdOx1 nCoV-19 trains the body to recognise and develop an immune response to the spike protein that helps to prevent infection from the SARS-CoV-2 virus if it later enters the body.


How does the Oxford-AstraZeneca vaccine compare to other vaccines in terms of efficacy?  

Preliminary data indicates that the vaccine is 70.4% effective. 70.4% is highly effective – more effective than the average flu vaccine. We’re going to need a range of vaccines, and in due course we’ll know which vaccines are most effective for different ages, and populations. The most important thing is to get people vaccinated, as this will help to bring the virus under control and prevent people from becoming severely ill.


Does the Oxford-AstraZeneca vaccine stop transmission, or stop you getting ill? 

The trial was designed to show whether the vaccine prevents you from getting ill; we will continue to gather data on asymptomatic infection, and other outcomes.The results of the trial so far (interim results) did show that the vaccine prevented people from getting severe COVID-19.  There were no cases of severe COVID-19 in participants who had the vaccine, and there were two cases in participants who had the control or placebo vaccines.


Will the Oxford-AstraZeneca vaccine become like the flu jab, and I'll need it every year? 

At this point we're unable to say, but other vaccines of this type are shown to produce an immune response lasting for a year or more.  



Page last updated: 
Friday, January 22, 2021