Covid-19: What you need to know today
On Monday, Nature carried a report which shows that we are slowly but surely figuring out the origin of the Sars-CoV-2 virus which causes the coronavirus disease (Covid-19). The report is about two related findings about the virus that came, not from the field, but the freezer. There have been many significant stories about the virus over the past 11 months, so this is something.
First, according to Nature, in two Shamel’s horseshoe bats captured in Cambodia in 2010, and stored in a freezer in a laboratory, scientists came across a coronavirus that seems to be related to Sars-CoV-2. Coronaviruses are family of RNA viruses (coronaviridae) that are known to cause diseases in humans, other mammals, and birds. Some of these are harmless – some common colds are caused by coronaviruses. But some, as we have discovered, can be dangerous. Severe Acute Respiratory Syndrome (Sars), Middle East Respiratory System (Mers), and Covid-19 are all severe diseases caused by coronaviruses. Mers, for instance, killed around a third of the people it infected (866 out of 2,519), but most experts admit that this is perhaps an overestimate. Many cases of Mers may have been mild, even undetected, causing nothing more than a minor illness, or nothing at all. Nature reports that the virus found in the Cambodian lab is being sequenced.
Second, the journal reports that a Japanese lab found a virus that shares 81% of its genome with Sars-CoV-2 in frozen samples of a Japanese horseshow bat captured in 2013. That isn’t much. There is a 99% similarity within a species. But travel further up the chain (to, say genus), and the divergence widens. For instance, humans and chimpanzees are from the same family (and also sub-family), Hominidae (and Homininae), and our genome is 96% similar to a chimpanzee’s. In general, scientists believe that a genomic similarity in excess of 95% can help them link two species on an evolutionary time-frame. The advantages of doing this with Sars-CoV-2 are clear – it can shed light on the provenance of the virus, even find out whether there was an intermediary in its transmission from bats to humans.
Interestingly, the Nature report says that the two findings, in Cambodia and Japan, may well mean that “as yet undiscovered Sars-CoV-2 relatives could be stored in lab freezers”, quoting Aaron Irving, a researcher at Zhejiang University in Hangzhou, China.
The report came on a day when a third vaccine candidate, AstraZeneca/Oxford’s, published interim results showing a 90% efficacy of the vaccine when administered as a half dose followed by a full one, and a 62% efficacy when administered as two full doses. The overall efficacy was 70.4%, which would have been considered high in any other context but the current one – the study’s results are being released in the wake of results released by Pfizer/BioNTech and Moderna that show a 95% efficacy of their own vaccine candidates. The AstraZeneca/Oxford vaccine is a vector vaccine, using a virus that causes cold in chimpanzees to transport a piece of genetic material from the spike protein of the Sars-CoV-2 virus to provoke an immune reaction from the body. The vaccine requires ordinary refrigeration, which means it will be easier to transport than Pfizer’s. And a 70% success rate isn’t bad, most flu vaccines have a success rate of around 50%.
The good news for India is that Serum Institute of India (SII), the world’s largest vaccine-maker, has an agreement with AstraZeneca to make the vaccine in India (and, in fact, took a risk that the vaccine would be successful to get a head start). The company has said 50% of the vaccines it makes will be for the local market. This means that if UK regulators approve the vaccine for use, Indian regulators may follow suit. If all of this does happen, the first doses of the vaccine may be available in India before the end of the year.
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