Nerve changes in eyes can help confirm ‘long Covid’ and Delta variant may be 1,000 times more infectious. Here’s an overview of some of the latest science on the novel coronavirus:

A general view shows the Rehazentrum Walenstadtberg rehabilitation clinic, amid the spread of the coronavirus disease, in Walenstadtberg, Switzerland June 14, 2021.
A general view shows the Rehazentrum Walenstadtberg rehabilitation clinic, amid the spread of the coronavirus disease, in Walenstadtberg, Switzerland June 14, 2021. (Reuters)

The following is a roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for Covid-19.

Changes in eyes help confirm long Covid diagnosis

Changes in nerve fibers in the eyes can help confirm a diagnosis of "long Covid" - debilitating symptoms that persist more than four week after recovery from the acute illness, according to new findings. Because nerve fiber damage is suspected to underlie some of these lingering symptoms, ophthalmologists used a non-invasive technique called corneal confocal microscopy to check for nerve damage in the cornea. 

In their study of 40 Covid-19 survivors - most of whom had not been sick enough to need extra oxygen - and 30 uninfected individuals, the researchers found "significant associations" between nerve fiber loss in the cornea and the presence and severity of long Covid symptoms related to nerves, muscles and bones. 

The corneal changes were most evident in patients with persistent neurological symptoms, such as loss of taste and smell, headache, dizziness, numbness and nerve pain, according to a report published on Monday in the British Journal of Ophthalmology. Corneas of patients with long Covid also contained more immune cells called dendritic cells, reflecting the body's response to injury. 

"We believe corneal confocal microscopy ... will allow clinicians to make the diagnosis of long Covid with greater confidence," said coauthor Dr. Rayaz Malik of Weill Cornell Medicine Qatar.

READ MORE: Covid studies: Dirty air worsens severity, beta variant deadlier

Mental health issues tied to higher Covid-19 death risk

Covid-19 patients with mental health disorders are more likely to die from the virus than patients without psychiatric or cognitive diagnoses, according to two new analyses. One study, published earlier this month in The Lancet Psychiatry, reviewed previously reported data on nearly 1.5 million Covid-19 patients. 

The risk of death was roughly 75 percent higher in patients with substance use disorders or intellectual disabilities and developmental disorders, and it was roughly doubled in those with psychotic or mood disorders. Covid-19 mortality risk was also linked with use of certain medications, such as antipsychotics, anxiety drugs, and antidepressants. 

The other study, published on Tuesday in JAMA Psychiatry, analysed data on more than 19,000 patients and found similar patterns. Dr. Bowen Chung of the University of California, Los Angeles, who was not involved in either study, said patients with mental health disorders tend to have other risk factors as well, such as diabetes, cardiovascular disease and respiratory disease, some of which can be linked to their medications.

"Antipsychotics in particular, have lots of metabolic effects, including obesity and high cholesterol," Chung said, and anxiety drugs can affect breathing. These individuals "also tend to have lower incomes and to not have as good access to healthcare."

Most with allergy to first mRNA shot can get second dose

Most people with allergic reactions to the first dose of an mRNA Covid-19 vaccine from either Pfizer/BioNTech or Moderna can safely receive the second dose, a new study shows. 

The rates of allergic reactions to these vaccines have been reported to be as high as 2 percent, with anaphylaxis, the most serious kind, occurring in up to 2.5 of every 10,000 vaccine recipients, the researchers said. 

They reviewed data on 189 adults with first-dose reactions to one of these vaccines, such as flushing, dizziness or lightheadedness, tingling, throat tightness, hives, and wheezing or shortness of breath. Most of these adults - 84 percent - received the second dose of the vaccine, with about a third taking an antihistamine beforehand. 

All of them tolerated the second dose, including those with first-dose anaphylactic reactions. Any potentially allergic symptoms that developed after the second dose were mild and easily controlled, the researchers reported on Monday in JAMA Internal Medicine. "Complete two-dose vaccination has become even more important with the Delta variant and we suspect there are many more people who did not get their second shot because of allergic symptoms," said coauthor Dr. Matthew Krantz from Vanderbilt University. "Our data suggest that most patients with immediate and potentially allergic reactions to mRNA Covid-19 vaccines tolerate a second dose," his team concluded.

Delta may be 1,000 times more infectious than original virus

The Delta variant of the coronavirus may be over a thousand times more infectious than the original version first identified in Wuhan, China, a Chinese study suggests. Tracking a recent outbreak, researchers found people infected with the Delta variant carry 1,260 times more virus in their noses compared to those infected in the first wave of the pandemic. The higher load means the virus spreads far more easily from person to person, increasing infections and hospitalisations, they reported ahead of peer review in a paper first posted on medRxiv earlier in July and updated on Friday. The interval between when people were exposed to infected individuals and when they themselves were diagnosed decreased from an average of 6 days in 2020 to 4 days during the Delta outbreak, the researchers found. The Delta variant is "outcompeting all other viruses because it just spreads so much more efficiently," said Shane Crotty of the La Jolla Institute for Immunology in San Diego, who was not involved in the Chinese study. In the United States, Delta accounts for about 83 percent of new infections, with unvaccinated people representing nearly 97 percent of severe cases.

Popular antacids not linked to severe Covid-19 outcomes

Widely-used antacid medications known as proton pump inhibitors (PPIs) are not linked with severe Covid-19 outcomes, a new study found. 

Researchers with the US Veterans Affairs Health Care System analysed data on nearly 15,000 veterans with positive Covid-19 tests, about 42 percent of whom were using PPIs such as Procter & Gamble's Prilosec (omeprazole), Takeda Pharmaceuticals' Prevacid (lansoprazole), and AstraZeneca's Nexium (esomeprazole). 

After taking patients' underlying Covid-19 risk factors into account, the risk of becoming sick enough to need mechanical ventilation or to die within two months of diagnosis was no different between regular PPI users and non-users, the researchers reported on Sunday on medRxiv ahead of peer review. "With respect to Covid-19," the researchers concluded, "patients and providers should feel safe to continue to use PPIs at the lowest effective dose for approved indications." 

READ MORE: Covid-19 science round-up: Jabs also protect unvaccinated household members

Source: Reuters