Frequently Asked Questions about COVID-19 vaccines

The questions and answers here have been developed using information from the British Society for Immunology, and are designed to cover some of the most common questions people have about the vaccines for COVID-19. This page will be updated as new insights and areas of interest emerge.


Do I need to get the vaccine if I have contracted COVID-19 and recovered?

Yes. There is a lot of uncertainty about how much immunity a person gains after natural infection. The levels of immunity that we can measure so far show a lot of individual variation – some people have very few antibodies after infection, but these antibodies can be boosted by vaccination. We can’t assume that everyone who has had COVID-19 would have enough immunity to protect them. It is likely that, in a significant proportion of the population, the vaccine will induce more effective and longer lasting immunity than that induced by infection. Hence it is recommended that everyone take the vaccine so that, if your immunity after disease is absent or low, it can be boosted.

Why should a young person take the vaccine when the risk of COVID-19 mortality is so low?

There is a huge variability in the symptoms and severity of COVID-19 disease between different people; from an infection with SARS-CoV-2 that doesn’t have any symptoms (asymptomatic infection) to severe COVID-19 disease resulting in hospitalisation and in some cases death. While younger people are usually at the less severe end of the spectrum this does not mean that the illness is not harmful to their health. In fact, there are many instances of long COVID that have blighted the lives of young people.

In addition, having the vaccine is likely to stop you being able to be part of the chain of infection that spreads the virus.

Does the AstraZeneca/Oxford vaccine being developed so quickly mean that it is less safe than other vaccines?

No, it doesn’t. The reasons that the vaccine was developed so quickly do not include cutting corners on safety. There are a few reasons that enabled the speed in 2020:

  1. Technology. This viral vector vaccine (in common with many of the approaches used for the other vaccine candidates) could be rapidly deployed for development and testing once the SARS-CoV-2 genetic sequence became known, but this was actually done on the back of almost ten years prior research using this method of producing vaccines. 
  2. Scientists. A LOT of scientists contributed to this, working extra long hours to make it work and to assess the results.
  3. Money. Normally raising money to develop a vaccine takes a long time. At each stage you have to stop and apply for more funding to carry out the next stage. Funding applications take a year or more. In 2020 for SARS-CoV-2, rapid investment of a lot of taxpayers’ money in many countries meant there weren’t the normal financial obstacles.
  4. Environment. Sometimes you can develop a vaccine but can’t test it until there is an epidemic in progress. There was no problem in this regard.
  5. Luck. Sometimes the target that is picked for vaccine studies, which is usually something seen on the outside of the virus, is not a good candidate for raising an immune response. The S protein target on SARS-CoV-2 that most vaccine companies picked to work with turns out to be an excellent target for activating the immune response.
  6. Volunteer test subjects. Last but definitely not least. Tens of thousands of volunteers took part in the safety trials and the randomised control trials so recruiting volunteers was not an issue as it may be under normal circumstances.
  7. Testing. Normally the various phases of safety testing happen sequentially, often because of financial restraints, in this case safety testing happened concurrently.

Are there any side effects from the vaccine?

Yes, but these are generally mild. As with all vaccines, because you are stimulating the immune system you may experience some mild flu-like symptoms, but these are temporary. The most common reactions are fatigue, headache and pain at the injection site. Some people might also get chills, joint pain or fever.

Should people with allergies take the vaccine?

Most people with allergies can have the vaccine. For example, some allergies, such as hay fever, are mild and do not pose a risk. The MHRA recommends that people with a history of anaphylaxis to food, an identified drug or vaccine, or an insect sting CAN receive any COVID-19 vaccine, as long as they are not known to be allergic to any component of the vaccine. The vaccine should not be given to people who have a history of immediate-onset anaphylaxis to any of the vaccine’s components. If you carry an EpiPen in case of allergic reaction, you have a history of immediate-onset anaphylaxis and so should discuss this with your doctor, nurse or pharmacist before getting the vaccine. People are asked to remain at the vaccination centre for a short period of time after receiving their vaccination so that the healthcare professionals can check there is no immediate adverse response to the vaccine.

Should I get the vaccine if I have a condition that affects my immune system?

Immunocompromised people are at high risk, so should get the vaccine. Although the AstraZeneca/Oxford COVID-19 vaccine contains a live adenovirus, it has been modified so that the virus is unable to replicate in humans, so unlike other ‘live’ vaccines, it is safe for people with compromised immune systems. However, because their immune systems may not be able to make a response to vaccine they should still take other precautions against the disease.

How are long term side effects tested/monitored?

Safety monitoring is to be continued for two years after the vaccine is released. There is a system in place (known as the yellow card system) to monitor and report adverse events immediately in a process known as pharmacovigilance. In the UK, this is carried out by the Medicines and Healthcare products Regulatory Agency.

Do I still need to wear a mask or observe social distancing after receiving the vaccine?

Yes. We know the vaccine can protect people from getting sick from the disease COVID-19 that is caused by the viral infection. However, it is still possible to become infected with COVID-19 if you have been vaccinated, so you could be an asymptomatic carrier who could pass the infection onto others who may be vulnerable.

Also, you will not be protected against the disease until at least three weeks after your first dose and you will not be fully protected until three weeks after your second dose.

How do viral vector vaccines work?

This type of vaccine uses an unrelated harmless virus (the viral vector) to deliver SARS-CoV-2 genetic material into the body. When administered, our cells use the genetic material to produce a specific viral protein, which is recognised by our immune system and triggers a response. This response builds immune memory, so your body can fight off the virus in the future.

Will the vaccine be effective against different variants of the SARS-CoV-2 virus?

The human immune system is diverse and dynamic so we think it will, but we don’t yet know this for a fact in all variants. We will need to monitor emerging virus variants and continually check (in the lab) whether serum from vaccinated people can neutralise them. This research is ongoing. If we find any significant reduction in neutralisation of variant viruses, we may need to subtly tweak the vaccine to induce a broader repertoire of neutralising antibodies.