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A single shot of Pfizer's Covid vaccine might NOT be enough to protect over-80s from South African variant, Cambridge study finds

 Delaying the second dose of the Pfizer coronavirus vaccine could leave some elderly patients at risk of catching the South African Covid variant, research suggests.

Laboratory tests by Cambridge University found that a single shot of the jab might not stimulate a strong enough immune response to kill the new strain in over-80s. 

Antibody levels only appeared to be protective after a second dose — but the researchers admitted the jab is still likely to be 'less effective' when dealing with the E484K mutation on the South African variant's spike protein. 

Experts believe the mutation — which is also present in the Brazilian Covid variants — helps the strain 'hide' from the body's natural defences. 

Top Government advisers and vaccine manufacturers insist the current crop of jabs should still work against the variant because the antibodies they make can still stop the disease from taking hold in the body. Antibodies — disease-fighting proteins created by vaccines and in response to previous infection — are also not the immune system's only layer of defence.

Scientists reacting to the findings said now was 'a good time to switch' away from Britain's one-dose strategy, which aims to get wider vaccine coverage quicker.

Regulators pivoted from their original plan to give people their second dose after 21 days when the Oxford University/AstraZeneca vaccine was approved at the end of December.

They pushed back the second dose for 12 weeks in a bid to give partial protection to as many vulnerable people as possible and drive down hospital admissions.

Already at least 105 Brits have been infected with the South African variant since December, which is likely to be an underestimate because Public Health England only looks at one in 10 random positive samples. 

No10 has already launched an effort to swab tens of thousands people in areas of England where cases of the South African variant have been discovered in people who haven't travelled out of the country.

In another worrying development today, health chiefs revealed the E484K mutation has now been found at least 11 times in Bristol among people infected with the Kent variant, raising fears it could become a permanent feature of the British strain. 

The three Covid variants causing international alarm emerged in Britain, South Africa and Brazil

The three Covid variants causing international alarm emerged in Britain, South Africa and Brazil

In a desperate attempt to keep track of the South African variant that experts fear could effect the current crop of vaccines, health officials will carry out swabs in Woking in Surrey, Walsall in the West Midlands, as well as parts of London, Kent, Hertfordshire and Lancashire

Ivy Smith, 97, who was among the first to get a Covid-19 vaccine at William Harvey Hospital in Kent, on the first day of the immunisation programme in December

Ivy Smith, 97, who was among the first to get a Covid-19 vaccine at William Harvey Hospital in Kent, on the first day of the immunisation programme in December 

The Cambridge study, which is yet to be peer-reviewed, took blood samples from 26 people, 15 of them over 80, who had received one dose of the Pfizer jab.

They then exposed them to synthetic versions of the South African and Kent variants and monitored their antibodies, disease-fighting proteins produced in the blood. 


The team found there were sufficient levels of antibodies to kill the Kent variant in all volunteers.

But when the E484K mutation was introduced, 10 times more antibodies were needed to neutralise the virus, the researchers said. 


Seven people, all over 80, had antibody levels that were insufficient to kill the virus after one dose of the vaccine. 

Only after a second dose, given three weeks later, were their antibody levels boosted to a level that neutralised the virus.

Dami Collier, a Cambridge researcher who co-led the work, said: 'A significant proportion of people aged over 80 may not have developed protective neutralising antibodies against infection three weeks after their first dose of the vaccine.'

Professor Ravi Gupta, the lead researcher, added: 'Our work suggests the vaccine is likely to be less effective when dealing with this (E484K) mutation.

'B1.1.7 [the Kent variant] will continue to acquire mutations seen in the other variants of concern, so we need to plan for the next generation of vaccines to have modifications to account for new variants.

'We also need to scale up vaccines as fast and as broadly as possible to get transmission down globally.'

Commenting on the findings, Professor Azra Ghani, chair in infectious disease epidemiology at Imperial College London, said: 'Although preliminary and small numbers, this research is important to improving our understanding of the vaccine responses in the most vulnerable age-groups. 

'With the South African variant now in the UK, it will be important to ensure that the most vulnerable groups are fully protected by the second dose. 

'Given the high coverage of first doses that has now been achieved in the first four priority groups coupled with the very strong age-gradient in risk, this would be a good point at which to switch to scheduling second doses alongside continuing the wider roll-out of first doses to the next priority groups.'

Dr Jonathan Stoye, a virologist at the Francis Crick Institute in London, added: 'The preprint... adds further support to a number of recent studies showing that SARS-CoV-2 is evolving to develop at least partial resistance to current vaccines.

'It suggests that some elderly individuals make relatively low immune responses to a single dose of vaccine. 

'This raises the possibility that, in some individuals, vaccine elicited immune responses may be too low to completely block virus replication but high enough to drive selection of resistant viruses: in other words that sub-optimal levels of antibody are driving virus evolution.

'This idea, if confirmed by subsequent studies, will be important in the development of vaccine delivery strategies regarding the timing of booster vaccine doses.' 

Yesterday it was revealed 11 Brits had caught the South African strain without any international travel links, which suggests the variant is already spreading in the community. 

In a bid to clamp down on the strain before it wreaks havoc on our immunisation programme, health chiefs today began mass community testing to try and weed out the South African variant.

Council, police and fire officials will go door to door dropping off Covid testing kits in parts of Surrey, Walsall, London, Kent, Hertfordshire and Lancashire as Health Secretary Matt Hancock warned last night 'we need to come down on it hard and we will'.

Health officials are anxious not to let another Covid variant run rampant, after Britain struggled to get a grip on the Kent strain which sparked a devastating second wave that plunged England into its third lockdown at the start of January.

Meanwhile, two separate studies in the US today suggested people who've previously been infected with coronavirus only need one shot of Pfizer or Moderna vaccines to enjoy protection. 

Results also showed that previously infected people developed 10 to 20 times more antibodies after one shot than those who received two doses and never had Covid. 

The findings, which are included in pre-prints and not yet reviewed, could provide a significant huge boost to the UK's vaccine drive. So far more than 3.5million Brits have officially caught and recovered from Covid, and may only need to be given one dose to be vaccinated.

This would free up as many doses to get wider vaccine coverage, or speed up how quickly the most vulnerable groups get their second dose. 

In the first paper, from researchers at the School of Medicine at Mount Sinai New York, 109 people were recruited, of whom 68 were negative for previous infection and 41 had had Covid-19 before. 

The authors said they are 'providing evidence that the antibody response to the first vaccine dose in individuals with pre-existing immunity is equal to or even exceeds' that found in people without prior infection, even after the second dose.

'Changing the policy to give these individuals only one dose of vaccine would not negatively impact on their antibody titers, spare them from unnecessary pain and free up many urgently needed vaccine doses,' they wrote.

The second paper, from the University of Maryland in the US, looked at antibody responses to a single dose of the Pfizer/BioNTech or Moderna vaccines in healthcare workers who had had a positive test for Covid-19, and compared them with those who were negative for antibodies to the virus.

Overall, 59 healthcare workers were involved in the study.

The results showed that those who had had Covid-19 previously had statistically significant higher levels of antibodies than those without, and 'had a classic secondary response to a single inoculation'.

The authors concluded: 'In times of vaccine shortage, and until correlates of protection are identified, our findings preliminarily suggest the following strategy as more evidence-based: a) a single dose of vaccine for patients already having had laboratory-confirmed Covid-19; and b) patients who have had laboratory-confirmed Covid-19 can be placed lower on the vaccination priority list.'

It came after PHE revealed today that the Kent Covid variant has started to mutate further to become more like the one that evolved in South Africa in what scientists have dubbed a 'worrying development'.

The E484K mutation has now been found at least 11 times in different cases of people infected with the Kent variant, Public Health England revealed, raising fears it could become a permanent feature of the British strain.

Both the Kent and South African variants already share one mutation, named N501Y, which makes the virus spread faster. And if this mutation, named E484K, sticks around as well the variants could become extremely similar.

E484K has been concerning scientists because it changes the shape of the virus's outer spike protein in a way that makes it difficult for the body to recognise it if it is only used to looking for older versions of the virus without the mutation.

This could raise the risk of reinfection or reduce how well vaccines work — but top Government advisers insist jabs should still be effective if taken in two doses. 

The jabs, however, have been made to specifically target an older version of the virus that didn't have the mutation, meaning that major changes to the virus might make it less able to spot and fix to it.

SAGE adviser Professor Calum Semple suggested today that the risk of the Kent variant – and other versions of the virus – continuing to evolve was 'inevitable' and 'will occur in time', and this mutation would likely be part of that.

Speaking about the threat, Professor Ravi Gupta, an infectious diseases expert at Cambridge University, said: 'The number of sequences is low at present, though enhanced surveillance is being undertaken by PHE. There may be more cases out there given how high transmission has been. We need to continue vaccinating and drive down transmission.'  

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