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UK Covid variant appears to linger in body for longer than other versions of virus, research suggests

Findings could explain heightened transmissibility of variant first detected in Kent, scientists say

Samuel Lovett
Thursday 18 February 2021 10:55 GMT
Nadhim Zahawi: No plans for international vaccine passports

The government’s current self-isolation protocol could fall under new scrutiny after research showed that the UK variant of the coronavirus appears to linger far longer in the body compared to other versions of the virus.

Scientists from a number of American universities, including Harvard and Yale, have found in research that has not yet been peer reviewed that it takes the immune system almost 30 per cent more time to clear infection caused by the variant first detected in Kent, which is now dominant in the British population.

Separate research from Public Health England and the University of Birmingham has shown that the UK variant generates higher viral loads in people.

Together, these two factors may explain the variant’s higher infectivity and widespread prevalence across the UK.

Follow Covid live: Lockdown takes effect as infections fall and Kent variant ‘stays in body longer’

The findings come as the government prepares to unveil its roadmap for exiting the current lockdown. Prime minister Boris Johnson said on Wednesday that he would adopt a data-led approach to lifting restrictions, stressing that England would ease measures cautiously.

Early indications suggest the UK’s vaccine rollout has begun to reduce hospital admissions and deaths in the over-80s - but the impact of the jab on transmission is yet to be fully determined, with Downing Street awaiting more conclusive data.

Vaccines minister Nadhim Zahawi said the government needed to make sure the jabs were bringing down the infection rates before committing to a clear exit strategy out of lockdown.

At the weekend, ministers were hopeful that schools could reopen from 8 March, with non-essential shops to follow and later pubs and restaurants.

Against this backdrop, a group of scientists in America has shed new light on the UK variant, known as B117.

In a pre-print published via Harvard University, which has yet to be peer reviewed, the researchers showed that the mean duration for when B117 was replicating and accumulating within the body was 5.3 days - compared to an average of two days for other variants.

It typically takes eight days for the immune system to clear B117, compared to 6.2 days for different variants, the study found.

And in total, the overall period of infection lasts 13.3 days for the UK variant and 8.2 days for non-B117 versions of the virus, researchers said.

The findings are preliminary and based on 65 people infected with Sars-CoV-2, including seven who were infected with the UK variant. The study participants were tested via PCR and underwent daily surveillance.

The scientists said that the data offered evidence that the UK variant might cause longer infections and that extended duration could contribute to the pathogen’s increased transmissibility.

“If borne out by additional data, a longer isolation period than the currently recommended 10 days after symptom onset may be needed to effectively interrupt secondary infections by this variant,” they said.

Dr Simon Clarke, an associate professor in cellular microbiology at the University of Reading, said the findings might not only highlight the increased transmissibility of B117 but could also go some way to explaining its increased lethality.

“It’s possible to envisage a situation where an increased time taken to clear the infection gives greater opportunity for the immune system to overreact and kill the patient,” he told The Independent.

Given the data, Dr Clarke said, the decision to cut the self-isolation period for contacts of people with confirmed coronavirus infection from 14 to 10 days looked unwise.

Self-isolation for contacts of people with confirmed coronavirus was shortened in December from 14 to 10 days. At the time, Dr Jenny Harries, deputy chief medical officer for England, said the policy change was based on a continuous accumulation of evidence through the pandemic.

Professor Lawrence Young, a virologist at the University of Warwick, described the Harvard paper as very interesting.

“This could mean that individuals infected with B117 are more infectious for longer and that current restrictions in terms of self-isolation would need to be extended,” he said.

But he said that more data from longitudinal [repeated] studies was needed.

Dr Alexander Edwards, an associate professor in biomedical technology at the University of Reading, said: “This is critical data, but also bear in mind this is reporting only a small number of individuals so it’s hard to draw conclusions yet.”

Details on the participants’ ages, comorbidities, symptom profile, antibody status and time since the onset of illness relative to swab sampling are needed, said Dr Julian Tang, a virologist at the University of Leicester.

Based on the latest research, scientists believe there may be two general reasons why a coronavirus variant is more transmissible.

“One factor is that there is a higher viral load, which means someone who is infected has a higher concentration of virus they're breathing out and therefore for any single contact with somebody who is susceptible, there's going to be more likelihood of transmission,” professor Deenan Pillay, a virologist at University College London, told The Independent.

“The second is that secretion of the virus may be for a longer period of time and therefore there's a longer period in which contact with somebody may lead to transmission. Both may play a role with B117, as it’s clear that it is more transmissible.”

He said that the Harvard data was premature and called for larger studies to be conducted before giving consideration to any changes in the current self-isolation period.

A study from PHE and the University of Birmingham has separately found that patients infected with the UK variant are more likely to have high viral loads. The findings were drawn from laboratory analysis of 641 positive coronavirus samples between 25 October and 25 November 2020.

“It also follows that if there is more replication that goes on with the new variant then that is compatible with the body taking longer to clear the body,” Prof Pillay said.

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