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COVID-19 vaccinations

COVID-19 vaccinations

January 25, 2021

COVID-19 vaccinations – the lowdown

COVID-19 vaccinations – the lowdown

With the NHS nationwide vaccination program in full flow with the Pfizer/BioNTech and AstraZeneca/Oxford University COVID-19 vaccines, here’s what you need to know about these vaccines, and the others in development.

The UK was the first country in the world to approve a COVID-19 vaccine and vaccinations are well underway with the UK government expecting “10s of millions” by the end of March[1].

How vaccines work

There are four categories of vaccines being developed by scientists around the world to protect against COVID-19, and they each work in slightly different ways.

Nucleic acid – RNA, in the case of COVID-19, or DNA

Nucleic acid vaccines use genetic material – either RNA or DNA – from the virus. In the case of the SARS‐CoV‐2 virus responsible for causing COVID-19, this is usually the viral spike protein. Once this genetic material gets into human cells, it uses their own protein factories to make the antigen that will trigger an immune response. As the antigen is produced inside our own cells and in large quantities, the immune reaction should be strong. A downside is that these vaccines need to be kept at ultra-cold temperatures, -20C or lower[2].

Viral vector

Viral vector vaccines also work by giving cells genetic instructions to produce antigens, but they do it using a harmless virus such as the one that causes the common cold, to deliver these instructions into the cell. As viral vector vaccines can mimic natural viral infection they too should cause a strong immune response. However, since many people may have already been exposed to the viruses being used as vectors, some may be immune to it, making the vaccine less effective[3].

Whole virus

Lots of our conventional vaccines use ‘whole viruses’ to trigger an immune response, but this is not as frightening as it sounds. Live attenuated vaccines use a weakened form of the virus that can still replicate without causing illness, and inactivated vaccines use viruses whose genetic material has been destroyed so they cannot infect us but can still trigger an immune response.

The downside is that there is a risk of live attenuated viruses causing infection in people with weak immune systems, and both types require cold storage. However, inactivated virus vaccines can be given to people with compromised immune systems[3].

Protein subunit vaccines

Subunit vaccines use pieces of the virus protein to trigger an immune response. This can minimise the risk of side effects, but also means the immune response may be weaker. Because of this, these vaccines often include adjuvants – substances which enhance the body's immune response[3].

The vaccines leading the pack

Although the Pfizer/BioNTech vaccine is the first to be approved for use in the UK, there are a number of others that are being considered for regulatory approval (at the time of writing). Here’s what you need to know about the various versions.


Developed in Germany

Type of vaccine: RNA

BioNTech, working together with Pfizer, started testing its BNT162 vaccine in humans as part of global trials, initially in Germany, and more recently in the USA and South Africa. By early November they had reported promising interim results in a trial of 43,000 participants. In their final efficacy analysis, Pfizer/BioNTech data showed the vaccine to be 95% effective against COVID-19.

The Pfizer/BioNTech product is an RNA vaccine and will need to be kept at temperatures below -70 degrees Celsius, which is why the first vaccinations are mainly being done in hospitals[1].

The UK Department of Health and Social Care and the Medicines, and the Healthcare products Regulatory Agency Regulatory (MHRA), have granted the Pfizer/BioNTech vaccine what is known as “authorisation for temporary supply” to be used to prevent COVID-19 in people aged 16 years of age and over. As with any new medicine in the UK, it will remain under close watch to enable the quick identification of new safety information.


Developed in Massachusetts, USA

Type of vaccine: RNA

The Moderna vaccine started phase 3 trials in July, with 30,000 healthy people enrolled from across the United States. The final trial results show the vaccine is 94% effective, and regulators in the US, Europe and the UK are considering it for an emergency licence. As with the Pfizer vaccine, this RNA vaccine will also need to be kept in ultra-cold freezers[1].

AstraZeneca/University of Oxford

Developed in the UK

Type of vaccine: viral vector

The ChAdOx1 vaccine, developed by the University of Oxford, was tested in phase 3 clinical trials with more than 10,000 people from across the UK, including children and the elderly, as well as in Brazil, the United States, India, and South Africa.

AstraZeneca is manufacturing 300 million doses in anticipation of the vaccine proving to be both safe and effective, and the UK has bought 4 million doses so far, although they can only be used once the vaccine is licensed. This vaccine is 90% effective, but it is fridge-stable, meaning that it can be transported anywhere in the world much more easily. At about US$4 per dose, it is also a fraction of the cost of others that are around US$26 per dose[1].

Other vaccines

Researchers from China decoded and then shared the genetic sequence of the SARS‐CoV‐2 virus with fellow scientists across the globe back in January, which means many labs have been working on a vaccine all at the same time. Here are some of the other vaccines being worked on:


Developed in China

Type of vaccine: inactivated

Sinovac recently began phase 3 trials involving volunteers in Brazil, Bangladesh, Indonesia and Turkey[1]. The effectiveness of this vaccine is not yet known, but, like the AstraZeneca vaccine, it will be fridge-stable.

Gamaleya Research Institute

Developed in Russia

Type of vaccine: viral vector

Russia has begun phase 3 trials of its non-replicating viral vector vaccine candidate (Sputnik V) with more than 40,000 volunteers in Russia, Latin America, the Middle East, Belarus, the United Arab Emirates and Venezuela[1].


Developed in USA

Type of vaccine: viral vector

J&J launched a phase 3 trial with 60,000 participants in September in Latin America and aims to make up to a billion doses in 20211. Trial results have not yet been published.


Developed in USA

Type of vaccine: protein subunit vaccine

Phase 3 trials started in the UK in September, followed by the USA[1].

COVID-19 vaccine roll-out in the UK

The order in which people will be offered the vaccine in the UK is based on advice from the Joint Committee on Vaccination and Immunisation (JCVI). The NHS is currently offering the COVID-19 vaccine to people most at risk from coronavirus, which at the time of writing is:·

  • some people aged 80 and over who already have a hospital appointment in the next few weeks

  • people who work in care homes

  • health care workers at high risk

The COVID-19 vaccine is given as an injection into the upper arm, with two doses at least 21 days apart. Although you may get some protection from the first dose, you only get the best protection a few weeks after getting the second dose[4].

How safe is the COVID-19 vaccine?

Every coronavirus vaccine must go through all the clinical trials and safety checks that every other licensed medicine goes through, in order to be approved for use.

The Pfizer/BioNTech vaccine currently being used in the UK has met strict standards of safety, quality and effectiveness set out by the independent Medicines and Healthcare products Regulatory Agency (MHRA). So far, thousands of people have been given this vaccine in clinical trials with no serious side effects or complications reported[4].

Most side effects are mild and should not last longer than a week, such as[4]:·

  • a sore arm where the needle went in

  • feeling tired

  • a headache

  • feeling achy

The vaccine does not contain any animal products, and it is very rare for anyone to have a serious reaction to the vaccine. If this does happen, it usually happens within minutes, and healthcare workers giving the vaccine are trained to deal with allergic reactions and treat them immediately.

The NHS says that although there is no evidence the vaccine is unsafe if you’re pregnant or breastfeeding, more evidence is needed so you should wait to have the COVID-19 vaccine if you are breastfeeding, pregnant, or trying to get pregnant[4].

These vaccines have been developed and rolled out at record speeds, which has led to some people raising concerns about their safety. However, the speed of vaccine development is because there are been a huge global effort to create these vaccines - the scientific community has been able to tap into massive data sets and a huge amount of funding.

How effective is the COVID-19 vaccine?

The Pfizer/BioNTech vaccine is 95% effective against COVID-19, so there is a small chance you might still get coronavirus even if you have the vaccine.

This means it is important to continue to follow social distancing guidance and wear a face covering, if you can, in places where it's hard to stay away from other people.

Dealing with doubts

Even if you are invited for a vaccination it is not compulsory so you do have a choice, and it’s normal to have questions about the vaccine. Your healthcare provider should be able to answer any queries you have, and Dr Kush Joshi, our UK medical lead here at Melio, also has some encouraging words.

“Most of us haven’t seen our elderly relatives for months, as well as other family members or friends with health conditions that put them at higher risk from the virus,” he says, “but if you’re vaccinated you are not giving them that risk.

“As well as doing it to protect yourself, and your nearest and dearest, spare a thought for the one million people in the UK who have had to shield since March. It’s about time they get to have a more normal life too, but the only way they can come out is if the vast majority of us get vaccinated. And even if a test has shown that you’ve already had COVID-19 you should still get vaccinated, because we know the antibodies you may have developed wain over time.

“The main reason life expectancy in the western world increased by roughly 30 years in the twentieth century was due to public health initiatives, including vaccination programmes -, but they only work if there’s a high uptake. This vaccine doesn’t mean we are out of the woods yet, and there is still a long way to go, but it is a huge step in the right direction.”





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