Eight facts about COVID-19 vaccines

Justin Hayde-West
Pharmaceutical Manager at Bupa UK
07 May 2021
Next review due May 2024

This is an updated version of an article first published on 16 January. Keep up-to-date with the latest guidelines on coronavirus at

Across the UK, millions of people have had COVID-19 vaccines through the NHS vaccination programme. This is an amazing achievement. Vaccines continue to be our best hope for ending the pandemic.

At the same time, some people still feel hesitant about vaccination. In some cases, this is due to misinformation being shared around. One in three of us have come across ‘fake news’ about COVID-19 vaccines.

Here are my eight key facts to put some of the claims you might be seeing or hearing into context.

Fact: Having a blood clot after COVID-19 vaccination is very rare

an infographic explaining having a blood clot after COVID-19 vaccination is very rare

You’ve probably heard reports about a link between the AstraZeneca vaccine and blood clots. More specifically, a rare type of blood clot called CVT (cerebral venous thrombosis) that has been happening along with low blood platelets. Research is still looking into this. But at this time, these incidents appear to be extremely rare. In fact, having COVID-19 probably puts you at a far higher risk of CVT than being vaccinated, according to researchers at the University of Oxford. Studies suggest that the risk is:

  • 4 in a million after a Pfizer or Moderna vaccine
  • 5 in a million after an AstraZeneca vaccine
  • 39 in a million after COVID-19 infection

Putting it into perspective further: you probably have more chance of getting a dangerous blood clot from taking a four-hour flight, than from having CVT from a COVID-19 vaccine. For most people, the benefits of being vaccinated far outweigh the potential risks.

However, if you have a health condition that puts you at higher risk of having a blood clot, you should speak to your health professional before having a vaccine. They can discuss the benefits and risks for you personally.

Health professionals are also being advised to offer people under 40 an alternative to the AstraZeneca vaccine, when one is available. That’s because, where blood clots were found to have happened after the AstraZeneca vaccine, there was a slightly higher risk for people in this age group. The risk was still very low for this group.

Fact: People who are trying for a baby or pregnant can still be vaccinated

People who are trying for a baby or pregnant can still have the COVID vaccine

Public Health England advise that you can still have a COVID-19 vaccine when trying for a baby, or if you are pregnant.

The Royal College of Gynaecologists and the Royal College of Midwives have stated that there’s no known way COVID-19 vaccines could affect fertility.

There’s also currently no evidence to suggest that COVID-19 vaccines can cause harm to pregnant women or their babies.

However, relatively fewer pregnant women have been given COVID-19 vaccines compared to the general population (in both trials and as part of national rollouts). That means we have less evidence to go on, so governments have been more cautious about offering vaccines to pregnant women.

Since the start of April, though, the advice in the UK has been updated based on recent data from the US. It now says that pregnant women should be offered a vaccine at the same time as other people of their age or COVID risk group. The advice also says it’s preferable for pregnant women to be offered the Pfizer and Moderna vaccines. Not because other vaccines are unsafe, but because there is less data about them being taken during pregnancy. You should speak with your health professional about the benefits and risks in your situation.

Fact: If you have COVID-19 antibodies, it’s not a reason to avoid vaccination

infographic explaining COVID-19 antibodies are not a reason to avoid vaccination

Some people have expressed a belief that, if an antibody test shows they’ve had COVID-19 before, then they don’t need to have a vaccine. They think that if they already have COVID-19 antibodies from being infected, that will protect them from being infected again. This is wrong for several reasons. You can be reinfected with COVID-19 after having it once. We don’t know how long immunity after COVID-19 infection lasts and there are signs that it may not be long. We also don’t know how strong that protection is while it lasts.

Vaccination, on the other hand, has been shown to offer highly reliable protection against illness from COVID-19. None of the 34,449 people in a trial of the AstraZeneca vaccine were hospitalised or became seriously ill, for example. Whether or not you have had COVID-19 before, vaccination is still important to reduce your risk of infection.

Fact: Vaccination cannot give you COVID-19

An infographic explaining vaccination cannot give you Covid-19

COVID-19 vaccines cannot cause COVID-19 infection. The myth that vaccination can give you COVID-19 seems to stem from a misunderstanding about what vaccines are and how they work.

Many traditional types of vaccine contain a weak or inactive form of the infection they protect against. Your body then develops antibodies. These fight off infection, without you experiencing the full symptoms of the disease. If you have contact with the disease again, your immune system remembers and protects you again. This means you have developed immunity to the disease. Because these vaccines do not contain any ‘live’ virus or bacteria, they cannot cause the infection they are designed to protect against.

The COVID-19 vaccines approved in the UK work in a slightly different way, but again do not contain any live COVID-19 infection and therefore cannot give you COVID-19.

  • The Pfizer-BioNTech and Moderna vaccines are ‘RNA vaccines’. They temporarily tell your body to create a particular part of the COVID-19 virus (called a ‘spike protein’).
  • The AstraZeneca-Oxford vaccine is a ‘viral vector’ vaccine. It uses a safe virus to introduce the ‘spike protein’.

In both cases, your body develops antibodies to the proteins. This usually leads to immunity from COVID-19.

It is possible, however, to have caught COVID-19, but not realise that you have done so until after your vaccination. There’s also the possibility of catching COVID-19 before the protective effects of a vaccine start working, which may be two to three weeks after your first dose.

Fact: The approved vaccines do not contain any animal products

An infographic showing approved vaccines do not contain animal products

The three COVID-19 vaccines approved in the UK do not contain any animal products. You can read lists of the ingredients found in each of the vaccines on the Coronavirus Yellowcard website. The website can also be used to report any side effects that you might experience after your vaccination.

You may be concerned about animal products. If this is because of your religious beliefs, it’s worth noting that many religious leaders and faith organisations have encouraged followers to have a COVID-19 vaccine when one is offered. These include the British Islamic Medical Council, Hindu Council UK and the Board of Deputies of British Jews.

Fact: The side effects of COVID-19 vaccines are usually mild

An infographic explaining mild side effects of Covid-19 vaccine

COVID-19 vaccines do not, for most people, cause more than mild side effects. These generally last for one or two days and may include:

  • arm pain
  • muscle or joint aches
  • fatigue
  • flu-like symptoms

Having symptoms like these is common after many types of vaccination. This is because vaccines trigger your immune system into action, and the response can be similar to having a mild form of the real infection.

People with certain allergies may be at risk of a more severe reaction. It’s important to speak to your doctor if you’ve had a severe allergic reaction in the past, to check that the vaccine will be suitable.

Side effects are looked at carefully as part of the rigorous clinical trials that new vaccines must go through. When the Medicines and Healthcare Products Regulatory Authority (MHRA) checks all the data from trials, the side effects that people in the trial have experienced are a big part of their considerations before they give approval.

Fact: The vaccine cannot affect your DNA

An infographic explaining the Covid-19 vaccine cannot affect your DNA

Rumours suggesting that COVID-19 vaccines can affect your DNA are not true.

The Pfizer-BioNTech and Moderna vaccines contain messenger RNA (mRNA) which give instructions to your cells. The mRNA instructs your body to make proteins found on the surface of the virus that causes COVID-19, which your body creates antibodies against. This usually leads to immunity. The mRNA usually stays in your body for a few days, before being broken down and removed by the body. It cannot influence or affect your DNA at all.

Fact: After vaccination, you still need to follow COVID-19 safety guidelines

An infographic explaining Covid-19 guidelines

Being vaccinated does not mean that you, or those around you, should be any less vigilant about following government COVID-19 guidance.

Firstly, it may take two to three weeks after your first vaccine dose to build up any protection. After your second vaccine dose this protection will increase. But even after this point, no vaccine approved against COVID-19 is completely effective in every case. We know that the COVID-19 vaccines can prevent people from being seriously ill from the infection. But to minimise the risk as much as possible, it’s important that all of us keep practising social distancing, wearing face masks and washing our hands regularly in line with the latest government guidance.

Justin Hayde-West
Justin Hayde-West
Pharmaceutical Manager at Bupa UK

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