Oxford Covid vaccine's 90% effectiveness is down to LUCK after a mistake in trials – and millions MORE could get doses

THE high effectiveness of the Oxford Covid vaccine is down to luck after a mistake in trials, its maker has admitted.

Trial data found giving participants two full doses resulted in 62 per cent protection against Covid-19.

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However, an initial half dose – followed up by a full dose a month later – was 90 per cent effective.

Only requiring a half dose of the vaccine will mean millions more Brits than first expected could be able to get a Covid jab, provided the Oxford proposal gets the go-ahead.

Experts think first priming the immune system with a weaker jab, before delivering a booster works better as it stops the body fighting back against the vaccine.

But Mene Pangalos, executive vice president at AstraZeneca, said the discovery was down to pure luck.

He said: "The reason we had the half-dose is serendipity."

When the trial started in April, university researchers began administering doses to Brit volunteers.

But some experienced much milder symptoms.

He added: "So we went back and checked… and we found out that they had underpredicted the dose of the vaccine by half."

However, they decided to continue the trial despite the initial error.

Britain has pre-ordered 100 million doses of the Oxford jab – which is expected to cost just £2 a time and can be stored at standard temperatures – with four million ready to be rolled out as soon as it gets regulatory approval.


The Oxford/AstraZeneca vaccine is cheaper and easier to distribute than the US's Pfizer and Moderna vaccines, which both revealed similarly promising results of around 95 per cent effectiveness last week.

It has also been shown to work in different age groups, including the elderly, and there were no hospitalised or severe cases in anyone who received the jab.

The preliminary data shows the vaccine works nine in ten times when it's first given as a half dose, then followed by a full dose a month later.

It’s not clear why, but the team think it could be that a smaller dose may be a better way of kicking the immune system into action.

The effectiveness drops to 62 per cent when given as two full doses at least one month apart, to give a combined average efficacy of 70 per cent – which experts say is more than most flu jabs.

Health Secretary Matt Hancock said that the Medicines and Healthcare products Regulatory Agency (MHRA) would now assess if the 90 per cent effectiveness dosing regime could be used.

He told BBC Breakfast: "I'm really very pleased, I really welcome these figures – this data that shows that the vaccine in the right dosage can be up to 90 per cent effective.

"Of course, it's vital that the independent regulator, the MHRA, will need to look at the data, will need to check to make sure that it's effective and safe of course.

"But we've got 100 million doses on order and, should all that go well, the bulk of the rollout will be in the new year."

Mr Hancock added that Brits could expect to see life return to normal by Easter next year.

We've got 100 million doses on order and. should all that go well, the bulk of the rollout will be in the new year

Prime Minister Boris Johnson tweeted: "Incredibly exciting news the Oxford vaccine has proved so effective in trials. There are still further safety checks ahead, but these are fantastic results. Well done to our brilliant scientists at @UniofOxford & @AstraZeneca, and all who volunteered in the trials."

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

Unlike the Pfizer vaccine – which has been found to be 95 per cent effective – the Oxford jab can be stored at more standard fridge temperatures.

Prof Andrew Pollard, chief investigator of the Oxford trial, said: "These findings show that we have an effective vaccine that will save many lives.

"Excitingly, we've found that one of our dosing regimens may be around 90 per cent effective and, if this dosing regime is used, more people could be vaccinated with planned vaccine supply."

Prof Pollard told the BBC Radio 4 Today programme that it was important to begin mass vaccinations as soon as possible.

Once we have protected the vulnerable in the population we will be able to start getting back to normal

"The most important thing to get us back to normal is to use these vaccines – all of the vaccines that are going to be available – as soon as possible," he said.

"Once we have protected the vulnerable in the population we will be able to start getting back to normal."

"We have just got to get on with this as soon as possible."


The results also revealed lower levels of asymptomatic infection in the smaller dose group, he said.

Prof Pollard added: "There is just a hint in the data at the moment that those who got that regime with higher protection, there is a suggestion that it was also able to reduce asymptomatic infection.

"If that is right, we might be able to halt the virus in its tracks and stop transmitting between people."

Speaking later a press briefing, he said not enough time has passed to know if people are still protected from the virus a year after being vaccinated.

How does the Oxford/AstraZeneca 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 that 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.

It differs from the Pfizer and Moderna vaccines because they use messenger RNA technology (mRNA).

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 actual virus is needed to create an mRNA vaccine. This means the rate at which the vaccine can be produced is accelerated.

"We only started giving the second doses of vaccine in the UK in August," he told reporters.

"The increase in disease, as you know, started towards the end of September and so most of the cases have only relatively recently accumulated both in the UK and in Brazil.

"So that means we just have not had enough time yet to be able to say whether, a year later, people are still as protected as they were at the beginning. So I think this is a 'watch this space' question."



The UK has placed orders for 100 million doses of the Oxford vaccine – enough to vaccinate most of the population – with rollout expected in the coming weeks if the jab is approved.

It also has orders for 40 million doses of a jab from Pfizer and BioNTech, which has been shown to be 95 per cent effective.

Another jab from Moderna, of which the UK has five million doses on order, is 95 per cent effective, according to trial data.

AstraZeneca has said it will have enough of its candidate vaccine for 20 million doses in Britain by the end of the year – and 200 million globally.

Operations executive Pam Cheng told a briefing the company is also manufacturing enough "active" drug substance for 70 million doses for the UK by the end of March next year and 700 million globally.

She said the company would keep the "active" drug substance in stock while it awaited regulatory approval around the world.

She said she expected that to translate into four million finished vaccine doses by the end of 2020, and 40 million finished doses by the end of Q1 next year.

Britain’s 350million vaccine doses

THE government has ordered 350million doses of Covid-19 vaccine, with some ready to roll out by December 1.

This includes 40million doses of the promising Pfizer shot, which was revealed to be 90 per cent effect last week.

These are the other vaccines which the government has pre-ordered:

Oxford/AstraZeneca: 100million doses
A weakened virus that causes colds in chimpanzees, it has been shown to generate a strong immune response against Covid-19.

It has been genetically changed so that it is impossible for it to grow in humans, making it safe for children, the elderly and people with pre-existing conditions.

Currently in phase-3 trials in the UK, USA, South Africa, Japan, Brazil and Kenya, more than 50,000 test patients have been given the vaccine. Early reviews have shown it to be safe.

A company in Australia has already started making millions of vials in the expectation that trials will be successful.

Novavax: 60million doses

Contains purified piece of the virus that causes Covid-19. When it is administered, the body recognises it as “foreign” and mounts a protective immune response.

It has been shown to generate more antibodies than in patients recovering from severe Covid-19 infections.

Currently in phase-3 clinical trials in the UK and USA.

GSK/Sanofi: 60million doses

Uses the same protein as one of Sanofi’s seasonal flu vaccines coupled with a booster.

In phase-1 clinical trials but early results have been positive.

Valneva: 60million doses
An inactivated whole virus vaccine designed to prompt the body into creating high levels of Covid-19 antibodies.

The government has invested in Valneva’s manufacturing facility in Livingston, Scotland, to create a major UK vaccine factory.

Currently in pre-trial research, with trials due to start in December.

Pfizer/BioNTech: 40million doses

Prevents Covid-19 infection by targeting the virus’s “spike protein”, effectively disabling it before it can cause any damage.

Tested on 40,000 patients, it is currently in phase-3 trials, but the first interim analysis has shown it is 90 per cent effective.

Janssen: 30million doses

Uses a modified common cold virus to act like a Trojan horse that can deploy the Covid-19 virus’s “spike protein” to human cells, causing the body to generate antibodies.

Phase-3 trials among 60,000 patients were recently halted temporarily after an unexplained illness in one volunteer. Trials have since resumed.

= 350million doses in total

Those calculations were based on using two full doses, she said, although trial data suggests higher efficacy when the initial shot is a half dose.

"If we go with a half dose you can imagine for the initial dose, we will be able to double the number of vaccinations here," she said.

She said the figures referred to the vaccine doses being manufactured by AstraZeneca, and not those being made by manufacturing partners.

The FTSE 100 edged up this morning rising almost one per cent to 6,379 after the announcement was made. 

Pascal Soriot, chief executive officer at AstraZeneca, said the news is an "important milestone" in the fight against the pandemic.

He added: "This vaccine's efficacy and safety confirm that it will be highly effective against Covid-19 and will have an immediate impact on this public health emergency.

The NHS’s leaked vaccine roll-out schedule

EVERY adult will be vaccinated against Covid by April under radical NHS plans to bring an end to the pandemic, leaked documents reveal.

Leaked plans, seen by Health Service Journal (HSJ), suggest health bosses are primed to immunise a record 44 million people within five months of a jab being available.

Under draft proposals vaccination will start in early December, depending on regulatory approval.

The ambitious provisional timetable sets out plans to protect the nation at breakneck speed – with five million jabs doled weekly:

Beginning of December: Care home residents, staff and care workers

Mid December: 80+

End of December: 70-80

Beginning of January: 65-70 and all high to moderate risk under 65s

Mid January: 50-65

Late January: 18-50s

The official schedule has yet to be decided. The Joint Committee on Vaccination and Immunisation (JCVI) has examined data on who suffers the worst outcomes from coronavirus and who is at highest risk of death.

Its interim guidance, which assumes the jab is safe and effective in all groups, says the order of priority should be:

  1. Older adults in a care home and care home workers
  2. All those aged 80 and over and health and social care workers, though they may move up the list
  3. Anyone 75 and over
  4. People aged 70 and over
  5. All those aged 65 and over
  6. High-risk adults under 65
  7. Moderate-risk adults under 65
  8. All those aged 60 and over
  9. All those 55 and over
  10. All those aged 50 and over
  11. The rest of the population, with priority yet to be determined.

The JCVI said the prioritisation could change if the first jab were not deemed suitable for, or effective in, older adults.

"Furthermore, the vaccine's simple supply chain and our no-profit pledge and commitment to broad, equitable and timely access means it will be affordable and globally available, supplying hundreds of millions of doses on approval."

Sarah Gilbert, professor of vaccinology at the University of Oxford, said: "The announcement today takes us another step closer to the time when we can use vaccines to bring an end to the devastation caused by (Covid-19).

"We will continue to work to provide the detailed information to regulators. It has been a privilege to be part of this multinational effort which will reap benefits for the whole world."

She said said scientists were "optimistic" that the Covid-19 vaccine would have good durability.

"When we did our MERS vaccine trial, that was with a single dose of a vaccine, and we did see very good, strong immune responses maintained a year after vaccination in that small clinical trial," she told a briefing.

"So, we're optimistic we're going to see good durability. There are grounds for believing that we will do, but we have to collect the data."

The results from the Oxford and AstraZeneca trial showed that the arm where one half dose was given followed by a full dose at least one month apart involved 2,741 people. This was the 90 per cent finding.

The other dosing regime involving 8,895 people showed 62 per cent efficacy when given as two full doses at least one month apart.

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