Oxford Covid-19 vaccine Q&A: How does it work and is it different to the Pfizer vaccine?

The Oxford/AstraZeneca vaccine was approved by the the Medicines and Healthcare Regulatory Agency (MHRA) on Wednesday, kickstarting a massive drive to give jabs to millions of people in January.

A Department of Health and Social Care spokesman said: “The Government has today accepted the recommendation from MHRA to authorise Oxford University/AstraZeneca’s Covid-19 vaccine for use.

“This follows rigorous clinical trials and a thorough analysis of the data by experts at the MHRA, which has concluded that the vaccine has met its strict standards of safety, quality and effectiveness.”

Professor Andrew Pollard, who is the director of the Oxford Vaccine Group and chief investigator of the Oxford vaccine trial, wrote in The Lancet medical journal on December 8: “This new vaccine has a good safety record and efficacy against the coronavirus”, following the release of the publication of the phase three trials data.

The vaccine was then submitted to the MHRA for approval.

Overall results from phase three of the Oxford/AstraZeneca trial, which had more than 11,500 volunteers from the UK and Brazil, show the vaccine is 70.4 per cent effective on average. However, when administered at a half dose and then a full dose the vaccine can be up to 90 per cent effective.

While the data was initially promising, the half-dose regime has not met approval standards. 

Instead, the MHRA has recommended that two full doses be given between 4-12 weeks apart. 

At an MHRA briefing, regulators said the data points to the vaccine being 70 per cent effective 22 days after the first dose is given. More analysis used to approve the jab was expected to be shared later on Wednesday.

The Prime Minister said in a press conference on Dec 30 that he would move “heaven and earth” to roll out the vaccine so restrictions can “recede into the past” by spring. 

He would go on to say that the government was working “as fast as we can” in order to get the vaccine rolled out. 

How does the AstraZeneca/Oxford vaccine work?

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

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.

How effective is it?

AstraZeneca – a British-Swedish multinational pharmaceutical and biopharmaceutical company with its headquarters in Cambridge – and Oxford University announced that their jab was effective in preventing many people getting ill and it has been shown to work in different age groups, including the elderly.

Partial immunity against Sars-Cov-2 is then detected approximately 22 days after administration of the first dose, the MHRA reported.

Data published in The Lancet in early December showed the vaccine was 62 per cent effective in preventing Covid-19 among a group of 4,440 people given two standard doses of the vaccine, when compared with 4,455 people given a placebo drug.

Of 1,367 people given a half first dose of the vaccine followed by a full second dose, there was 90 per cent protection against Covid-19 when compared with a control group of 1,374 people. Again, this dosing regime was not approved on Wednesday. 

The overall Lancet data, which was peer-reviewed, set out full results from clinical trials of more than 20,000 people.

Among the people given the placebo drug, 10 were admitted to hospital with coronavirus, including two with severe Covid-19 which resulted in one death.

However, among those receiving the vaccine, there were no hospital admissions or severe cases.

The combined analysis from both dosing regimens resulted in an average efficacy of 70.4 per cent.

However, Deputy Chief Medical Officer Professor Jonathan Van Tam said in a press conference on Dec 30 that although people receiving the vaccine would be protected, he could not provide assurance they would not still “pose a hazard” to others in terms of passing on the virus.

“We will know quite quickly within a couple of months the impact of these vaccines on reducing severe illness in the population,” he said.

“We don’t know if the vaccines will reduce transmission but Public Health England have their finger on the pulse.”

He would also go onto say that it would take up to two weeks for scientists to confirm the AstraZeneca and Pfizer vaccines were effective against the new strains of Covid-19.

How many doses does the UK have?

The UK has secured 100 million doses of the Oxford/AstraZeneca vaccine, this is the most the Government has ordered out of all of the potential vaccine candidates. 

The order is enough to vaccinate 50 million people.

AstraZeneca said it aimed to supply millions of doses in the first quarter of next year as part of an agreement with the Government.

There will be four million doses available post authorisation and tens of millions of doses in the first quarter of next year.

A specific schedule is difficult to establish as batches need to be quality approved by the MHRA.

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. 

The Pfizer and Modern vaccines have both been approved in the US.

The UK Government began the rollout of the Pfizer vaccine earlier this month.

Unlike the Pfizer vaccine, the Oxford jab does not require ultra-low temperatures.

The Oxford jab requires temperatures between 2C and 8C and can be stored for at least six months. 

This is the typical temperature of a domestic refrigerator and this will make deployment of the vaccine much easier and faster.

What about antibodies and T-cells?

The Pfizer, Oxford/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/AstraZeneca 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, venture capitalist 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.

Where is it being manufactured?

While there are some doses coming from Europe in the very first instance, the majority will be provided from the UK supply chain.

Do you need two doses of the Oxford vaccine?

The MHRA has recommended the over 18s should receive two doses to be administered with an interval of between four and 12 weeks.

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.

Can pregnant women have the vaccine?

Pregnant women and breastfeeding mothers have now been given the green light to take either the Oxford and Pfizer coronavirus vaccines following an appropriate case-by-case risk evaluation with their healthcare practitioner.

This is a reversal of previous advice which was put in place as precautionary measure.

Traditionally pregnant women are not included in clinical trials, but following a review the MHRA are recommending pregnant women be given the opportunity to receive the vaccine as as there is no evidence they would be at risk.

Dr June Raine, chief executive of the MHRA, said: “Our advice to date has been that given that in initial lack of evidence on a precautionary basis, use of a vaccine wasn’t recommended in pregnancy and women with breastfeeding should not be given the vaccine.

“But now that we have reviewed further data that has become available, the Commission on Human medicines has advised that the vaccine can be considered for use in pregnancy when the potential benefits outweigh the risks following an individual discussion with every woman.”

Can people with allergies have the vaccine?

The roll-out of the Pfizer vaccine was halted for those who are known to suffer from severe allergic reactions following a handful of adverse events in the initial distribution of the vaccine. 

There were some concerns that this would also apply to the Oxford jab. 

However, following a review, the UK regulatory body has recommended both the Pfizer and Oxford vaccine are safe to administer to those with food or medicine allergies. 

Only those who have a known history of reacting to vaccines in the past should proceed with caution.

Sir Munir Pirmohamed, clinical pharmacologist and geneticist, and chairman of Commission on Human Medicine Expert Working Group, said. “We’ve come to the recommendation people with a known history of reacting to any specific ingredients of vaccine should not have it. But people with allergies to other medicines or food can have the vaccine.”

Dr June Raine added that “at least 800,000 in the UK, probably a million and a half in the US” have already received the Pfizer vaccine. 

There has been “no additional concerns and this gives us further assurance that the risk of anaphylaxis can be managed through standard clinical guidance and an observation period following vaccination of at least 15 minutes.”

When will roll-out of the Oxford vaccine start?

The Oxford vaccine will be rolled out from January 4 across the country under plans being drawn up by ministers, The Telegraph can reveal.

The Government is aiming for two million people to receive their first dose of either the Oxford vaccine or the Pfizer jab within a fortnight as part of a major ramping up of the inoculation programme.

The Telegraph can also disclose that mass vaccination centres at sports stadiums and conference venues are primed to launch in the second week of January.

An army of more than 10,000 medics and volunteers has been recruited by the NHS to help deliver the Oxford Covid-19 vaccine

Source: Oxford Covid-19 vaccine Q&A: How does it work and is it different to the Pfizer vaccine?

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