A potential Covid-19 vaccine developed by AstraZeneca Plc and Oxford University produced a strong immune response in older adults, giving hope it may protect some of those most vulnerable to the disease, it has been announced.

The data, reported in part last month but published in full in The Lancet medical journal on Thursday, suggest that those aged over 70 – who are at higher risk of serious illness and death from Covid-19 – could build robust immunity to the pandemic disease, researchers said.

Here’s what we know about how it works…

How does the AstraZeneca/Oxford vaccine work?

The vaccine – called ChAdOx1 nCoV-19 – uses a harmless, weakened version of a common virus which causes a cold in chimpanzees.

Researchers have already used this technology to produce vaccines against a number of pathogens including flu, Zika and Middle East respiratory syndrome (Mers).

The virus is genetically modified so it is impossible for it to grow in humans, PA Media reports.

Scientists have transferred the genetic instructions for coronavirus’s specific “spike protein” – which it needs to invade cells – to the vaccine.

When the vaccine enters cells inside the body, it uses this genetic code to produce the surface spike protein of the coronavirus.

This induces an immune response, priming the immune system to attack coronavirus if it infects the body.

Does it differ to Pfizer and Moderna’s vaccines?

Yes. The jabs from Pfizer and Moderna are messenger RNA (mRNA) vaccines.

Conventional vaccines are produced using weakened forms of the virus, but mRNAs use only the virus’s genetic code.

An mRNA vaccine is injected into the body where it enters cells and tells them to create antigens.

These antigens are recognised by the immune system and prepare it to fight coronavirus.

No virus is needed to create an mRNA vaccine. This means the rate at which the vaccine can be produced is accelerated.

What are the implications for developing countries?

Professor Andrew Pollard, the head of Oxford trial team, said the vaccine is being developed for distribution “everywhere” including places with limited infrastructure for the ultra-cold storage that some vaccines require.

The mRNA vaccines such as those made by Pfizer and Moderna will likely require being stored at extremely cold temperatures, around -70C.

This throws up a number of logistical challenges when considering how they will be transported en masse over long distances and to hotter parts of the world.

Because the protein-based Oxford vaccine will only require refrigerating at around 2C-8C, it will be far easier to transport and store worldwide.

Speaking on BBC Radio 4’s Today programme, Prof Pollard said: “We’re really looking globally, we want to be able to get to every corner of the world if indeed the vaccine is shown to work.

“The thing that matters with vaccines is the impact it can have, and that is, can you get it to people and are they being vaccinated, so until you’ve got high coverage and you’re able to prevent the disease in those who are most vulnerable, we won’t get there.”

The United Nations Children’s Fund (UNICEF) has already begun a huge operation to have 520 million syringes stored in its warehouses across the globe by the end of the year, ready and waiting for the roll out of a safe vaccine.

But there are concerns poorer countries could be priced out of the Oxford vaccine in the future.

Moderna has already said it will profit from a successful vaccine while Pfizer said in the summer the company will “price our potential vaccine consistent with the urgent global health emergency that we’re facing”.

They added: “A vaccine is meaningless if people are unable to afford it.”

What about antibodies and T-cells?

The Pfizer, AstraZeneca and Moderna vaccines have been shown to provoke both an antibody and T-cell response.

Antibodies are proteins that bind to the body’s foreign invaders and tell the immune system it needs to take action.

T-cells are a type of white blood cell which hunt down infected cells in the body and destroy them.

Nearly all effective vaccines induce both responses.

The Oxford vaccine induces robust antibody and T-cell responses across people of all ages, the data indicates.

Can the Oxford vaccine be manufactured to scale?

Yes. The UK government has secured 100 million doses as part of its contract, enough for most of the population.

The head of the UK Vaccine Taskforce, Kate Bingham, has said she is confident it can be produced at scale.

Experts hope the jab could be ready to go and rolled out shortly.

Can this vaccine help the elderly?

There have been concerns that a Covid-19 vaccine will not work as well on elderly people, much like the annual flu jab.

However, data from the Oxford-AstraZeneca trial suggests there have been “similar” immune responses among younger and older adults.

The results show that the vaccine is better tolerated in older people compared with younger adults, and produces a similar immune response in old and young adults.