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COVID19: Delaying second dose of vaccine increases risk of new resistant strain, Sage papers reveal

Warning over ‘realistic possibility’ of resistant strains of the virus emerging

London, Jan 23: Delaying doses of coronavirus inoculations will increase the chances of a vaccine-resistant strain of Covid-19 emerging, scientists have warned.

In new reports, released by the Scientific Advisory Group for Emergencies (Sage), experts also warned that resistant new variants were a “realistic possibility” driven by the virus reacting to increasing levels of natural immunity among the population.

In papers released on Friday, Sage scientists said there was an “increased risk of virus replication under partial immunity after one dose than after two doses, so in the short term, delaying the second dose would be expected to somewhat increase the probability of emergence of vaccine resistance – but probably from a low base.

“Is such an increase material?

It is not currently possible to quantify the probability of emergence of vaccine resistance as a result of the delayed second dose, but it is likely to be small.

“In the current circumstances the unquantifiable but likely small probability of the delayed second dose generating a vaccine escape mutant must be weighed against the measurable benefits of doubling the speed with which the most vulnerable can be given vaccine-induced protection.”

But the paper added: “Given what we have observed recently with the variants B.1.1.7 and B1.351, it is a realistic possibility that over time immune escape variants will emerge, most likely driven by increasing population immunity following natural infection.”It warned: “Vaccine efficacy after one dose should be carefully monitored to inform future vaccine policy.”

Sir Patrick Vallance, the chief scientific adviser, told a Downing Street press conference on Friday that the virus was likely to be around “forever”, adding:

The most risky thing in terms of new mutation is to have very high prevalence. The more the virus is transmitting and replicating between people the more likely it will get a mutation, and that is what is happening around the world”.

That’s the biggest risk.

There is always some risk if you start to have partial immunity, but there is also a benefit which is partial immunity can actually stop the infection quicker.”

Chris Whitty, the U.K government’s chief medical adviser, said:

“All of medicine is about balance of risk. Our overall view was that the balance of risk was firmly in favour at this stage of the epidemic in the UK of having many more people vaccinated but that does mean a delay. That particular risk was a much smaller risk of not having people vaccinated which was the alternative.”

All viruses mutate and natural variations in the Sars-CoV-2 virus have been identified across the globe and the Sage paper said this was likely to happen at a “faster rate” as greater numbers of people become immune after infection.

It added: “Most mutations will be inconsequential, but a few may, by chance, confer a functional advantage over others and, through natural selection may become dominant laboratory-generated variants.”

It said there was “theoretical and experimental data supporting the possibility” that the virus could generate new variants which would “evade” antibody therapies, convalescent plasma, and vaccines as well as natural immunity.

The paper said vaccinated people who went on to develop Covid-19 need to have their virus genetically sequenced “as quickly as possible to understand whether viral variation may explain the breakthrough”.

Increased sequencing of tests would help identify new clusters and spot changes as they emerge after the vaccine rollout.

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CT scan effective tool to detect, determine severity of Covid-19 cases: DAK

(Asian News Hub) – Doctors Association Kashmir (DAK) on Saturday said chest CT scan is an effective tool to detect and determine the severity of Covid-19 cases.

“CT scan helps in diagnosing and predicting the outcome of Covid-19 patients,” said DAK President and influenza expert Dr Nisar ul Hassan.

“More Covid cases are detected with a CT scan of the chest than through RT-PCR,” he said.

Dr Hassan said we see many patients who test negative on RT-PCR test, but show CT features consistent with Covid-19 disease.

 “Many infected patients go unreported as only RT-PCR positive cases are reported. We have a large number of patients who test positive through CT, but are not reported,” he said.

Dr Hassan said RT-PCR, which uses swab for the detection of Covid-19 infection has a sensitivity of 60%-70%. That means more than 30% of positive cases may be missed by the test.

“Another swab test which is now widely used is rapid antigen test. It has a sensitivity of around 50 percent, which raises the possibility of missing more than half of the positive cases,” he said.

 “Low sensitivity of swab tests implies that many patients with Covid-19 infection may not be identified and consequently are not isolated from healthy population. And these individuals will continue to spread the disease in the community,” he added.

“Studies have shown that CT has a greater sensitivity ranging from 86% and 98% for detecting positive cases, while having a lower false negative rate than the lab tests,” Dr Nisar said

“In a study of 1,014 patients published in the Journal Radiology, researchers in china found that 88% of the patients showed chest CT findings indicative of Covid-19, while RT-PCR test detected only 59 percent of cases. Among those with negative swab test results, 75 percent had positive chest CT findings,” he said.

The DAK President said not only is CT useful in identifying Covid cases, it also tells us about the severity of the disease.

“That would guide treatment and help reduce the risk of death in Covid patients and save lives,” he said.

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Scientists have taught bees to smell the coronavirus, can identify a case within seconds

(Asian News Hub) – Scientists in the Netherlands have trained bees to identify COVID-19 through their sense of smell, according to a press release from Wageningen University.

The research was conducted on more than 150 bees in Wageningen University’s bio-veterinary research laboratory.

The scientists trained the bees by giving them a treat – a sugar-water solution – every time they were exposed to the scent of a mink infected with COVID-19. Each time the bees were exposed to a non-infected sample, they wouldn’t get a reward (a process known as Pavlovian conditioning).

Eventually, the bees could identify an infected sample within a few seconds – and would then stick out their tongues like clockwork to collect the sugar water.

Bees aren’t the first animals to detect COVID-19 by scent. Researchers have also trained dogs to distinguish between positive and negative COVID-19 samples from human saliva or sweat with fairly high levels of accuracy. A small German study found that dogs could identify positive COVID-19 samples 94% of the time.

That’s because metabolic changes from the coronavirus make an infected person’s bodily fluids smell slightly different than those of a non-infected person.But researchers still aren’t sure whether animals are the best bet for sniffing out COVID-19 cases outside the lab.

“No one is saying they can replace a PCR machine, but they could be very promising,” Holger Volk, a veterinary neurologist, told Nature.

PCR machines are what lab technicians use to process standard COVID-19 swab tests.

At the very least, certain animals could be useful for identifying COVID-19 in places or countries in which high-tech laboratory equipment is scarce or inaccessible.Wageningen scientists, for instance, are working on a prototype of a machine that could automatically train multiple bees at once, then uses their skills to test for coronavirus aerosols (tiny virus-laden particles) in the surrounding environment.

AGENCY

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Delhi hospital study finds 16 per cent vaccinated individuals tested positive for Covid-19

(Asian News Hub) – A small-scale study on 113 healthcare workers who had received at least one vaccine dose at a private hospital in Delhi found that 18 tested positive for Covid but all except one had mild symptoms.

The study, published in the peer-reviewed journal Diabetes and Metabolic Syndrome: Clinical Research and Reviews on May 3, was conducted on employees of the Fortis Centre of Excellence for Diabetes, 
Metabolic Diseases and Endocrinology in Delhi.

The participants in the study by researchers at Fortis, National Diabetes, Obesity and Cholesterol Foundation, and Diabetes Foundation (India), New Delhi, included doctors, nutritionists, nurses, paramedical workers, and maintenance staff.

Of the 113 in the study, 107 had received the second dose of the vaccine.

Taken in percentage form, the study found that 
breakthrough infections — Covid infection in vaccinated individuals — occurred in 15.9 per cent (18 persons) of the vaccinated individuals and 95 per cent had mild symptoms. Of these, 17 incurred the infection after the second dose and one person. Except one person who required hospitalisation, all others had mild Covid-19 disease, the researchers said.

According to the study, of the breakthrough infections in 18 persons, 17 incurred the infection after the second dose. These 17 had got their second dose after a mean of 34.8 days following the first jab. All were symptomatic with fever and half of them had sore throat and cough.

The study covered 123 employees “ 75 males, 48 females with mean age 42 — 113 of whom were vaccinated. Of them, 28 people had received the 
Covaxin vaccine from Bharat Biotech, and 85 the 
Covishield preventive from the Oxford/AstraZeneca stable. Covishield, Covaxin and Sputnik V are the three Covid-19 vaccines currently approved for use in India. The three vaccines claim efficacy of 81 per cent, 70 per cent, and 92 per cent respectively.

However, Sputnik V has not yet hit the market. The researchers noted that breakthrough infections after adequate vaccinations are a matter of concern but adequate data on these infections is not available. Vaccines have effectiveness risk of getting Covid-19 infections by 70-90 per cent, and also shield from severe infection. It is possible, therefore, some people who are fully vaccinated against Covid-19 may get Covid-19 infection, the authors of the study said.

They explained that unpublished data from India as well as published reports from other parts of the world indicate these infections are occurring but are rare. In addition, it appears that these breakthrough infections are either asymptomatic or mild in nature, the authors added. The authors acknowledged some limitations of their study: its small sample size, and absence of data on obesity and co-morbid diseases which are important determinants of severity of Covid-19. They also did not test asymptomatic infections.

PTI

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