Today Oxford welcomed the news that the UK regulator, the MHRA, has authorised the use of its coronavirus vaccine for use in the UK. Our FAQ offers further details about the vaccine and the approval.

Efficacy and dosing 

Is your vaccine effective? 

Yes. We’re confident that our vaccine is highly effective, and safe. In results published to date, no one vaccinated with our vaccine was hospitalised with coronavirus. 

Our interim data, based on a pooled analysis pre-agreed with regulators, indicates that the vaccine is 70.4% effective. Full details on the subgroup analyses are published in the Lancet. 

The UK Medicines and Healthcare products Regulatory Agency (MHRA) has provided authorisation for temporary supply of the ChAdOx1 nCoV-19 coronavirus vaccine for the active immunisation of individuals 18 years or older. 

Why are there different efficacy numbers?  

The 70.4% is a weighted average of different dosing regimens across all of the trials. 

Different figures relate to differing sub-groups of volunteers and you can read more about these in our publication of all of these data in the peer-reviewed journal, The Lancet

You’ve previously said that a different dosing regimen would give a more effective vaccine. Why should I take this less effective one? 

The UK Medicines and Healthcare products Regulatory Agency (MHRA) has provided authorisation for temporary supply of the ChAdOx1 nCoV-19 coronavirus vaccine for the active immunisation of individuals 18 years or older. 

The authorisation is recommended as a two dose regimen, given as two standard doses with a flexible inter-dose interval of four to twelve weeks, which was shown in clinical trials to be safe and effective at preventing symptomatic COVID-19, with no severe cases and no hospitalisations more than 14 days after the first injection. 

Together with the ease of refrigerated distribution and storage, this will enable AstraZeneca to make tens of millions of doses available in the first quarter of 2021 on a rolling basis so we can start protecting people around the world as soon as possible. 

Vaccinations are just one tool for combating the virus; we need multiple vaccines to be successful and these will only be effective if they are used by people around the world, in combination with other public health measures. 

Why does the MHRA say your vaccine has a 70% efficacy, when in The Lancet you announced different efficacy results? 

The MHRA has made an independent assessment of the efficacy and agrees with the primary analysis of 70.4% for two-dose efficacy as previously reported in The Lancet.  

The Lancet publication provides full details of the subgroup analyses. 

Why is the efficacy of two full doses 70.4%: for one full dose 73% (after 22 days) and 52.6% with any dose after one dose? Why are they all so different?  

The 73% protection after the first dose that is presented in the MHRA label that accompanies the vaccine is a further analysis for the MHRA which provides information about the efficacy during the short period between the first and second dose, in the recommended schedule. 

This is included in one of the analyses in The Lancet paper but has not been separated out in the same way as requested by the MHRA for the label. These analyses are all presented in The Lancet publication providing a full explanation of the numbers. 

Why have the second dose if the first gives me a higher efficacy?  

The first dose efficacy gives an indication of protection for a short period between the two doses, the second dose strengthens the immune response and is expected to provide a more durable immune response. The numbers are not statistically different from one another. 

Why didn’t you perform the same analysis as the MHRA for your Lancet paper?  

These are the same analyses as in the Lancet paper, with some additions specifically required for the label. The primary analysis for the assessment of interim results in the trial was prespecified following extensive discussions with the regulators, and the trial team have followed normal procedure by following that analysis plan, with a small number of additional analyses included at the request of the Lancet’s peer reviewers. The Lancet publication has a full published analysis. 

Who will decide the interval between vaccine doses? 

The MHRA, supported by JCVI, has recommended a two-dose regimen with a flexible interval of four to twelve weeks between vaccinations. 

Why do you think the MHRA has said efficacy increases over time (up to 12 weeks) - although also appears to decrease from 73% to 70% with the single dose vs the double dose? 

The MHRA label shows that the immune response is stronger with longer intervals between the two doses, and this may translate into better protection. Statistically- speaking the efficacy is not different between these two numbers 

Should I wait until 8-12 weeks for my second dose?  

The Department of Health will advise on policy for vaccination with this new licensed and efficacious vaccine, and when to make your second appointment. 

Does the interval between doses change the effectiveness of the vaccine?  

Our interim results show that the vaccine works well, after the second dose, with an interval of between four and twelve weeks as licensed by MHRA. The MHRA have reviewed the data and believe that the protection is most robust when the booster dose is delivered between four and twelve weeks. 

The data suggest that a longer interval between doses may increase the effectiveness of the vaccine after the second dose. However more data from the trials will provide greater certainty about this effect. 

What is the best dosing interval to protect people?  

The MHRA and JCVI have recommended a two-dose regimen, with the vaccines administered between four and twelve weeks apart.  

Why does the effectiveness of the vaccine change according to the dosing interval?  

Longer intervals between vaccine doses are known to increase the size of the booster with other vaccines as well. 

Are two doses needed and how soon after vaccination are people given protection?  

Our vaccine gives partial immunity beyond day 22 of first dose with our initial results showing that two doses provide more robust protection beyond three months. 

In your study, there was a big variation in when people got their booster vaccine. Does that impact the data?  

Our early investigations of the efficacy did not find statistically significant differences in efficacy between groups receiving their booster at different times, but we will investigate this possibility further.  

Will this vaccine protect people from the new strains of coronavirus?  

There is no evidence so far that the vaccines will be any less effective against this new strain of the virus. The virus is expected to change through mutation to make new variants, as had happened recently in the South East UK, which has made the virus more transmissible. Changes in the virus are being monitored closely, and it's important we continue to remain vigilant for changes in the future. 

Distribution  

When can I get this vaccine? 

National governments will determine the best way to distribute to the public, often considering those who are at most risk from the virus first. 

This efficacy result is based on data from younger (18–55 years old) adults – how do you know that it is safe for older adults? 

The MHRA have approved this vaccine and have come to the conclusion that the dosing schedule can remain the same for these groups, we know further results are due in the next couple of months and will build on existing knowledge for older adults. 

We have previously published data on the safety and immunogenicity of the vaccine that suggests that it is well tolerated and safe for use by older adults. 

Will this vaccine be given to children? 

The safety and immunogenicity of this vaccine has not yet been assessed in under 18s but we are planning trials in children. 

Will this vaccine be given to pregnant or breastfeeding women? 

The MHRA labelling gives advice in this respect. 

Safety and safety data 

Will there be any allergic reactions? 

The MHRA labelling summarises the safety profile of the vaccine, including special warnings and precautions for use. 

The MHRA have advised that people with a known history of allergy to the ingredients in the vaccine should not receive a vaccination, but people with known food allergies are able to receive this vaccine. 

Allergic reactions to medicines do happen, and for vaccines they can happen in around every one in a million times. All new medicines are tracked by the NHS, so they will get warnings if we see more frequent reactions. Furthermore, some people will be asked to join a special active monitoring system for this vaccine. 

The MHRA have also announced that people do not require testing prior to having the vaccine, so can receive it if they’ve already had Covid. 

Can you guarantee that no one will have an allergic reaction, fall seriously ill or even die by taking the vaccine?  

While this is a new vaccine, the technology used to develop it is something we’ve been studying for nearly ten years. There are risks associated with any medicine, and our trials have indicated that this vaccine does not lead to any unexpected reactions and has a similar safety profile to previous vaccines of this type. 

In any large trial of a new medicine, incidents are followed up rigorously with an independent group of safety experts. We’ve collected a large safety database during the trial, and this will be submitted to regulators for review. We also continue to monitor the volunteers who were the first to receive this vaccine for any longer-term effects. 

Allergic reactions to medicines do happen, and for vaccines they can happen in around every one in a million times. All new medicines are tracked by the NHS, so they will get warnings if we see more frequent reactions. 

Were the cases which caused the trial to pause on the vaccine or the placebo? 

In any large trial of a new medicine, incidents are followed up rigorously with an independent group of safety experts. We’ve collected a large safety database during the trial, and this will be submitted to regulators for review. We also continue to monitor the volunteers who were the first to receive this vaccine for any longer-term effects.   

Were there any pauses to the trial because of safety incidents?  

Yes. Regulators reviewed and then restarted the trials confident it was safe to do so.  

Of nearly 24,000 trial volunteers, and over 74,000 ‘person-months’ of safety follow up, only three from 175 reported serious adverse events were possibly related to the vaccine.   

Of these, one was considered ‘possibly related’ to the ChAdOx1 nCoV-19 vaccine, one occurred in the control group, and a further case of severe fever in the vaccinated group was considered to be an expected vaccine-related event.  

Safety is our absolute priority in our trials and so our protocol requires the chief investigator to pause the study if there are any unexplained illnesses that occur in the clinical trial. These are expected to occur in any population of more than 20,000 people, but when they do, the greatest scrutiny should be undertaken by independent experts and the regulators to check that it is safe for the trials to proceed.   

Which vulnerable groups were included in the trial? When will you include more?  

Our Phase III trials were open to people with many underlying health conditions, and these are represented in the trial, and further trials are designed to specifically recruit from these vulnerable groups. 

Will your vaccine be safe for immunocompromised people?

ChAdOx1 nCoV-19 cannot replicate in humans and does not lead to the production of more virions after vaccination, and therefore it is safe to use in the immunocompromised. Our ongoing trials have included HIV infected adults, and will publish full data on these cohorts in due course, with the existing data showing a good safety profile for the vaccine.

Does the vaccine 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 results 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 should not have further doses of vaccines 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 vaccine and public health 

How long will people be protected from the virus for with this vaccine? 

At this point we cannot say, but other vaccines of this type which we have worked on in the past are proven to provide immune responses that can persist for a year or more. 

Does this mean that we can expect to be back to ‘normal’ soon?  

Distributing any vaccine quickly will be a huge logistical challenge, but we’re optimistic that now regulatory approval has been granted in the UK and around the world, this will put us on the path to ‘normality’. 

It’s important that the whole world is vaccinated, and we have a responsibility to drive delivery throughout the world - a major task for manufacturers and distributors through 2021.  

Our partner AstraZeneca has rapidly secured supply agreements towards 3 billion doses and has set up parallel supply chains across more than 15 countries, so that once regulatory approval is received, distribution can begin on a rolling basis with the ability to supply 100-200 million doses per month at the height of manufacturing. 

If people are being vaccinated already, can’t life go back to ‘normal’? 

This is just one tool for combating the virus; we need multiple vaccines to be successful and these will only be effective if they are used by people around the world, in combination with other public health measures. 

Your vaccine isn’t as ‘effective’ as others. Why not leave it to them? 

The key with any vaccine is the potential for impact on public health, including how quickly it can be distributed. Ours can be quickly and easily distributed around the world, using existing logistics, and easily stored in a fridge.  

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. Our vaccine can be deployed quickly in existing health settings, which will help to stop the further spread of this disease and save lives while we learn more and more about how to prevent and treat it.  

Does this vaccine stop transmission, or stop you getting ill?  

Our 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.  

Will this 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.   

Can you take both your vaccine and the others that are out there, 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.  

How much does the vaccine cost?  

As part of our agreement with our partner AstraZeneca, the 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 as we join forces to combat the coronavirus pandemic. 

The vaccine trial and research 

What was the purpose of this research study?   

Our study set out to test a new vaccine against COVID-19. 

We began by evaluating safety in healthy adults aged 18-55, before extending the trial to all healthy adults and some with well-controlled health conditions. Once we've gathered these data, along with efficacy data, we plan to include children in the trial. 

These trials, held at sites across the UK, Brazil, South Africa and Kenya, involve over 23,000 volunteers, half of whom received a placebo vaccine and half of whom received the ChAdOx1 nCov-2019 coronavirus vaccine. 

Extensive follow up with these volunteers allows us to determine the efficacy of the vaccine, and be assured that it is safe. 

What is the vaccine being tested?   

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. The SARS-CoV-2 coronavirus uses its spike protein to bind to ACE2 receptors on human cells to gain entry to the cells and cause an infection.   

By vaccinating with ChAdOx1 nCoV-19, we are hoping to make the body recognise and develop an immune response to the Spike protein that will help stop the SARS-CoV-2 virus from entering human cells and therefore prevent infection.    

Has the vaccine been tested on animals?   

Our collaborators at Rocky Mountain Laboratories (NIAID/NIH) have conducted a rapid yet thorough investigation and demonstrated good safety and efficacy of a single dose of ChAdOx1 nCoV-19 in the rhesus macaque model that they had previously established. We were able to review the data before vaccinations in the clinical trial were initiated. There were also additional animal studies which assessed the vaccine in mice and pigs, and further studies underway in Australia and the UK, and the results will be published once those studies are complete.   

What does the study involve?   

In the UK, this study aims to enrol around 12,000 adults from across the country. To date we have enrolled over 10,000 healthy adult volunteers aged 18 to over 70, including some with well-controlled health conditions, such as high blood pressure.    

Volunteers in both the Phase II and Phase III parts of the trial will be randomised to receive either the ChAdOx1 nCoV-19 vaccine or a licensed vaccine (MenACWY) that will be used as a ‘control’ for comparison.   

Researchers are assessing the immune response to the vaccine of people in these groups, to find out if there is variation.  

Later parts of the study will allow assessment of how well the vaccine works to prevent people from becoming infected with COVID-19. 

We’re also working with regulators and our ethical committees to develop a protocol to begin a trial in people under 18. 

What's the next stage of your team's work on this?  

The trials continue with volunteers being followed up for 12 months and we hope to have final data beyond this interim analysis soon. We’re also working with regulators and our ethical committees to develop a protocol to begin a trial in people under 18. 


The University of Oxford's vaccine development work

Our vaccine work is progressing quickly. To ensure you have the latest information or to find out more about the vaccine trial, please check our latest COVID-19 research news or visit the COVID-19 vaccine trial website.

The University of Oxford's vaccine development work
Close up of syringe and vaccine vial

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