What different types of Covid-19 vaccine are there?

Standfirst

There are hundreds of Covid-19 vaccines in development, and some have produced very positive results in phase III clinical trials. So, how do some of the different vaccines work and compare?

Listing image
Illustration of four medical jars lined up horizontally. Within the jars lies drawings of viruses and dna.
Credit
Wellcome
File size
390907 bytes
Image width
1600px
Image height
900px
Filename
FINAL_ExplainerThumbnails_Ex9_What_Different_Types_Of_Covid_Vaccine_Are_There-1600x900.png
Image
Illustration of four medical jars lined up horizontally. Within the jars lies drawings of viruses and dna.
Download allowed
On
Content
Group title
How do vaccines work?
Admin title
How do vaccines work?
Group
Body

All vaccines work by teaching our bodies to recognise and fight the pathogen in a safe way. They encourage our immune system to produce antibodies, T-cells or both, so that if we encounter the infection later our immune system knows how to defend against it. 

Video embed
Accordion slice
Body

How do vaccines work?

Anna Mouser, Policy and Advocacy Lead, Vaccines: Love to know how you explain to people how vaccines work.

Professor Luke O'Neill, Chair of Biochemistry at Trinity College Dublin: The best analogy I've used over the years is like, the bad guy arrives in town and the immune system puts up wanted posters, right, so when the real bad guy comes back and the next time he's recognised more quickly, I suppose. And in essence, what vaccines do is there are parts of – in this case, Covid-9 – the virus and then the immune system can recognise that part and then get trained to recognise it when the real bad guy arrives with those parts as well. And you make loads of antibodies to the spike. Your T cells come out, they're a very important part of the immune system as well. And they come out in numbers and then when the virus – the real virus – infects you, those antibodies and T cells are there, they've identified the virus. I call it a 'boot camp' sometimes.

Mouser: Bootcamp?

O'Neill: Yeah, there's two very important cell types: B cells and T cells. And what the vaccine does is it brings them out in numbers – from the fortress, if you will you, know. And then when you get challenged with the virus, then you have loads of troops there ready to fight the virus. And they stop you getting infected.

Title
Expand to read the transcript
Body

Vaccines can be made using many different technologies. The Covid-19 vaccines that are currently the most advanced are using four different approaches:

  • viral vector
  • RNA
  • 'whole' virus
  • protein subunit. 
Image
Illustration showing how different Covid-19 vaccines work including RNA, viral vector, whole virus and protein subunit
File size
1290289 bytes
Image width
2500px
Image height
2375px
Filename
how-do-different-covid-19-vaccines-work.jpg
Image
Illustration showing how different Covid-19 vaccines work including RNA, viral vector, whole virus and protein subunit
Download allowed
On
Body

Viral vector vaccines

A harmless virus is altered by introducing part of the disease-causing virus’ genetic code, such as the code for Covid-19’s ‘spike’ protein. 

The harmless virus transports the code into our cells – in a similar way to RNA vaccines – which then start to produce the protein.

This triggers an immune response, priming our immune system to attack the real virus later.

Oxford-AstraZeneca is the first viral vector vaccine to be approved for Covid-19. More are in late-stage research, such as CanSino Biologics, Gamaleya Research Institute and Johnson & Johnson. They all use adenoviruses – a group of viruses that cause the common cold – as the vector or carrier. 

Another example of a viral vector vaccine is the Ervebo (rVSV-ZEBOV) Ebola vaccine – it uses the vesicular stomatitis virus as the carrier.

RNA vaccines

Messenger RNA is a sequence of genetic code which our bodies use all the time – it tells our cells what proteins to build so they can function. 

To produce an RNA vaccine, scientists develop a synthetic version of the virus’ messenger RNA. 

When this is injected into our bodies, cells read it as an instruction to start building the relevant viral protein, for example Covid-19's 'spike' protein. This prompts our immune system to respond, and in doing so it learns how to protect against future Covid-19 infection.

Two RNA Covid-19 vaccines have been approved for use: Pfizer-BioNTech and Moderna. Both have reported high levels of vaccine efficacy – around 95%.

They are the first RNA vaccines ever to be approved for use against any disease. However, researchers have been using the technology for a while, and people have been given RNA vaccines in clinical trials for other diseases, like cancer.

‘Whole’ virus vaccines

These vaccines could be:

  • Inactivated – a version of the virus is inactivated by being exposed to heat, chemicals or radiation. 
  • Virus-like particle – a version of the virus, closely resembling the real thing, is created artificially, however it doesn’t contain any genetic material, so it’s not infectious.   

These vaccines cannot cause the disease, but will cause our bodies to produce an immune response which will protect against future infection. 

Some of the most advanced inactivated Covid-19 vaccines in development include Sinovac, Bharat Biotech and two by Sinopharm. Examples of existing inactivated vaccines include the whooping cough, rabies and hepatitis A vaccines.

One vaccine in phase III clinical trials is virus-like particle: Medicago Inc. An example of an existing vaccine is the HPV/cervical cancer vaccine. 

Protein subunit vaccines

A small piece of the virus’ genetic code is inserted into another cell – perhaps a bacterial, yeast, mammalian or insect cell. The code contains instructions for this cell to start building the virus protein, for example the Covid-19 ‘spike’ protein.

Cells like this act as factories, building large quantities of the protein – which is then extracted, purified and used as the active ingredient in the vaccine. 

When it is injected, our bodies learn to recognise the viral protein so that they can mount an immune response which protects against future infection. 

Some of the most advanced Covid-19 vaccines using this approach include Novavax and Chinese Academy of Sciences.

An example of an existing protein subunit vaccine is for hepatitis B, which uses yeast cells to build the virus protein. 

Group title
How do the different Covid-19 vaccines compare?
Admin title
How do the different vaccine approaches compare?
Group
Body

The different vaccine approaches present different opportunities and challenges, which is why we’ll need a range of vaccines to get control of the pandemic.
 

Image
An infographic showing how some of the different Covid-19 vaccines compare
File size
688059 bytes
Image width
1600px
Image height
1320px
Filename
SP-7286.XX_Covid-19_How_Covid_Vaccines_Compare_Infographic_amend08.09.21.jpg
Image
An infographic showing how some of the different Covid-19 vaccines compare
Download allowed
On
Body

Are they suitable for people who are immunocompromised?

Although vaccines are usually safe for people who are immunocompromised, people who are severely so are sometimes advised to avoid live vaccines, because even the weakened virus can make them very sick. Encouragingly, early studies suggest that all four of the vaccine technologies currently being used are suitable for people who are immunocompromised, and as none of these technologies use 'live' virus, they should not pose a problem in this respect.

How many doses are required?

Most approved vaccines to date require two doses, spaced weeks apart to achieve full immunisation, with the exception of the single dose Johnson & Johnson viral vector vaccine. 

How are they stored?

Many vaccines need to be refrigerated - usually around 2 to 8C - however RNA vaccines need to be stored at at least -70C, which could pose problems for transporting and storing it, particularly in low and middle-income countries where refrigeration facilities may be limited. The Moderna vaccine can be stored at fridge temperature for 30 days (2 to 8C) once delivered to healthcare facilities which is encouraging, but requires -20C for long-term storage and transportation.

Group title
How can we make sure that Covid-19 vaccines are accessible to everyone?
Admin title
How can we make sure that Covid-19 vaccines are accessible to everyone?
Group
Body

To overcome the pandemic, we have to overcome it everywhere in the world. But we will only succeed if vaccines are available and affordable to all countries. 

The COVID-19 Vaccine Global Access Facility (COVAX) is working to make this happen, by ensuring that all participating countries, regardless of income levels, will have equal access to the vaccines in its portfolio once they are developed. But only three of the vaccines currently in phase III clinical trials are part of the COVAX portfolio. 

There is a serious danger that low-income countries may be shut out of vaccine access, as they are less able to procure deals directly with pharmaceutical companies. For example, wealthy countries have signed deals to buy roughly 600 million doses of the Pfizer-BioNTech vaccine (which is not part of the COVAX portfolio). This accounts for nearly half of Pfizer-BioNTech's total production capacity up to the end of 2021.

So countries that have secured large numbers of vaccine doses, like the UK, must commit to donate their suitable excess doses to COVAX, so that they too can be fairly distributed.

This explainer was first published on 8 December 2020.

Group title
Related content
Group
Listing layout
Image card with CTA link (Horizontal card)
Content
Listing summary

There are hundreds of Covid-19 vaccines in development, and some have produced very positive results in phase III clinical trials. How do some of the different vaccines work and compare?

Banner styling
Compact
Banner image
A researcher fills a test tube
Credit
Wellcome
File size
415639 bytes
Image width
1200px
Image height
675px
Filename
what-different-types-of-covid-19-vaccine-are-there-161220.jpg
Image
A researcher fills a test tube
Download allowed
On
Exclude from listings
Off
Meta title
What different types of Covid-19 vaccine are there? | News | Wellcome
Meta description
How do some of the different Covid-19 vaccines work and compare? Approaches include RNA, viral vector, whole virus and protein subunit. The companies developing them include Pfizer-BioNTech, Oxford-AstraZeneca, Moderna and Johnson & Johnson.
Ordering date
Article type
Explainer
Published date
Article content type
News
Add noindex
Off
Statement
Off
7 minutes
Grey Background
Off
Include audio player
On