Covid-19 vaccine efficacy against Delta variant declines after three months

British researchers find Pfizer-BioNTech and AstraZeneca lost effectiveness even after two shots

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  Relatives embrace as they arrive from the US at Heathrow's Terminal 5 in west London.

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  A mother embraces her son as he arrives from the US at Heathrow. People fully vaccinated in the US and EU, except France, can now travel to England without having to quarantine on arrival.

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  Families reunite as they arrive from the US at Heathrow.

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  Relatives embrace as they arrive from the United States at Heathrow's Terminal 5.

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  Mothers Debbie Greaves, center, and Karen Tyler, right, who don't know each other, wait to greet their sons arriving on different flights at Terminal 5 of Heathrow Airport.

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  Circus lighting technician Ryan Dobie receives a vaccination as circus performers look on at a new ‘Pop Up’ vaccination centre in the Big Top of Circus Extreme in Shibden Park in Halifax.

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  Dr Lisa Pickles, clinical lead for the local vaccination program, prepares a syringe at the Big Top of Circus Extreme vaccination clinic.

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  Travellers exit from an arrivals gate at St Pancras International station following the arrival of a Eurostar train from Paris, in London.

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  An NHS worker prepares for patients at a pop-up vaccination centre during a four-day Covid-19 vaccine festival in Langdon Park, east London.

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  A person receives a dose of the Pfizer/BioNTech vaccine at the Central Middlesex Hospital in London.

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  A health worker wears a mask which bears a slogan asking for fair pay for nurses during a demonstration about pay in the UK's National Health Service, in London.

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  Gardener Gemma Hearn making a final trim of the Hampton Court Maze before it reopens to the public at Hampton Court Palace, in south-west London.

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  Customers queue for the London Eye attraction on the South Bank of the River Thames in central London.

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  An NHS public health message in view of Westminster Abbey in London.

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  A shopper wearing a face covering crosses the street at Oxford Circus in London.

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Covid-19 vaccines become less effective against the Delta variant three months after full vaccination, according to new research by the University of Oxford.

The results of the large UK study looked at how the Pfizer-BioNTech and AstraZeneca vaccines protect patients against Covid-19.

Probably you get some protection against more severe disease for a few years. The whole point of the vaccines is to stop people from getting ill and dying

Prof Paul Hunter,
University of East Anglia

Researchers found that 90 days after the second shot the vaccines' efficacy in preventing infections slipped to 75 per cent and 61 per cent respectively.

That was down from 85 per cent and 68 per cent respectively, seen two weeks after a second dose.

The decline in efficacy was more pronounced among those aged 35 years and over, than among younger case studies.

Scientists also found that when vaccinated people were infected with Delta, they had similar levels of virus in their bodies as those who had not had the injections.

This could imply that those who are vaccinated could still spread the virus. It also raises questions over whether herd immunity can be achieved even in countries of mostly vaccinated people.

Findings ‘not surprising’

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  All school staff and children aged 16 and over must be vaccinated to enter school premises in Abu Dhabi. All photos: Khushnum Bhandari / The National

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  Dalaa Alaa Aladwan, 14, from Rosary School is vaccinated at Seha Vaccination Centre, Abu Dhabi Cruise Terminal, Zayed Port.

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  Abdullah Al Mansoori, 17, a student at Zayed University, is vaccinated before entering the army at Seha Vaccination Centre, Abu Dhabi Cruise Terminal, Zayed Port.

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  Nour Khaled, 14, is vaccinated before attending Al Najah Private School in September.

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  Miranda Mali, 33, a kindergarten teacher at Sharjah American International School, is vaccinated before school begins.

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  A nurse explains how vaccination works to Kavita Kumari, a Hindi teacher at Sunrise English Private School.

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  A nurse prepares the vaccine kit at Seha Vaccination Centre, Abu Dhabi Cruise Terminal, Zayed Port.

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  Dalaa Alaa Aladwan, 14, from Rosary School, signs forms to be vaccinated.

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  Nurses speak with patients at the Seha Vaccination Centre, Abu Dhabi Cruise Terminal, Zayed Port.

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  The registration area at Seha Vaccination Centre, Abu Dhabi Cruise Terminal, Zayed Port.

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  Nurses work at Seha Vaccination Centre, Abu Dhabi Cruise Terminal, Zayed Port.

Prof Paul Hunter, a professor in medicine and infectious diseases specialist at the University of East Anglia in the UK, said the results of the latest study were "not surprising".

He that while the vaccines' effectiveness at preventing mild infections starts to fall away in a matter of months, the shots continued to prevent severe disease for far longer.

Immunity against mild disease, from vaccination or previous infection, was, he said, "short-lived". But the immunity to the more severe viral pneumonia from Covid-19 that can result in hospital admission and death "lasts a lot longer".

"Probably you get some protection against more severe disease for a few years, so what this means is that the vaccines are not going to stop the spread of the virus. Most of us who work in the area have known this for at least six months," he said.

"Herd immunity is not and never was going to be achievable. The whole point of the vaccines is to stop people from getting ill and dying."

While the new study indicates a reduction in vaccine efficacy over time, Prof David Taylor, professor emeritus of pharmaceutical and public health policy at University College London, said the vaccines were performing "relatively well".

"The real [challenge] for the world is getting production up to the level so we can supply poor world [countries], which isn't happening at the moment," he said.

He said, however, that scientists and governments would look for enhanced vaccines that were more effective against the Delta variant and other variants, and that such "tweaked" shots could be used widely as boosters.

The UK survey, run by the University of Oxford and the Office for National Statistics, analysed more than three million PCR tests from a random sample of people.

The results are likely to encourage more countries to offer booster shots for fully vaccinated people. The policy is already in place in the UAE.

Health officials in the Emirates recommend that people have booster shots six months after their second vaccine dose, unless they are considered vulnerable, in which case they should have it after three months.

This week, US President Joe Biden announced that Americans who have had both doses of Pfizer-BioNTech or Moderna will be allowed a booster after eight months.

Israel this month started giving third doses of Pfizer-BioNTech to the elderly. Initial results show they have been 86 per cent effective for people aged 60 and over.