Tag: covid severity

Categories : COVID Immune SystemTags :

New Discovery Explains How SARS-CoV-2 Evades Anti-viral Immunity

On By ModernMedia
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The novel coronavirus SARS-CoV-2 has an enzyme that can counteract a cell’s innate defence mechanism against viruses, explaining why it is more infectious than the previous SARS and MERS-causing viruses. This discovery, from Kobe University, may point the way to the development of more effective drugs against this and possibly similar, future diseases.

When a virus attacks, the body’s immune response has two basic layers of defence: the innate and the adaptive immune systems. While the adaptive immune system grows stronger against a specific pathogen as the body is exposed to it multiple times and which forms the basis of vaccinations, the innate immune system is an assortment of molecular mechanisms that work against a broad range of pathogens at a basic level. The Kobe University virologist SHOJI Ikuo says, “The new coronavirus, however, is so infectious that we wondered what clever mechanisms the virus employs to evade the innate immune system so effectively.”

Shoji’s team previously worked on the immune response to hepatitis viruses and investigated the role of a molecular tag called “ISG15” the innate immune system attaches to the virus’s building blocks. Having learned that the novel coronavirus has an enzyme that is especially effective in removing this tag, he decided to use his team’s expertise to elucidate the effect of the ISG15 tag on the coronavirus and the mechanism of the virus’s countermeasures.

In a paper in the Journal of Virology, the Kobe University-led team is now the first to report that the ISG15 tag gets attached to a specific location on the virus’s nucleocapsid protein, the scaffold that packages the pathogen’s genetic material. For the virus to assemble, many copies of the nucleocapsid protein need to attach to each other, but the ISG15 tag prevents this, which is the mechanism behind the tag’s antiviral action. “However, the novel coronavirus also has an enzyme that can remove the tags from its nucleocapsid, recovering its ability to assemble new viruses and thus overcoming the innate immune response,” explains Shoji.

The novel coronavirus shares many traits with the SARS and MERS viruses, which all belong to the same family of viruses – which also have an enzyme that can remove the ISG15 tag. But their versions are less efficient at it than the one in the novel coronavirus, Shoji’s team found. And in fact, it has been reported recently that the previous viruses’ enzymes have a different primary target. “These results suggest that the novel coronavirus is simply better at evading this aspect of the innate immune system’s defence mechanism, which explains why it is so infectious,” says Shoji.

But understanding just why the novel coronavirus is so effective also points the way to developing more effective treatments. The Kobe University researcher explains: “We may be able to develop new antiviral drugs if we can inhibit the function of the viral enzyme that removes the ISG15 tag. Future therapeutic strategies may also include antiviral agents that directly target the nucleocapsid protein, or a combination of these two approaches.”

Source: Kobe University

Categories : COVID Substance UseTags :

Contrary to Some Expectations, Cannabis Use Increases COVID Severity

On By ModernMedia
Photo by Thought Catalog on Unsplash

At the start of the COVID pandemic in 2020, scientists quickly recognised that a handful of characteristics, including age, smoking history, high body mass index (BMI) and the presence of other diseases such as diabetes, increased the risk of severe disease and death. But one suggested risk factor remains unconfirmed more than four years later: cannabis use. Evidence has emerged over time indicating both protective and harmful effects.

Now, a new study by researchers at Washington University School of Medicine in St. Louis points decisively to the latter: Cannabis is linked to an increased risk of serious illness for those with COVID.

The study, published in JAMA Network Open, analysed the health records of 72 501 people seen for COVID at Midwestern US health centres during the first two years of the pandemic. The researchers found that people who reported using any form of cannabis at least once in the year before developing COVID were significantly more likely to need hospitalisation and intensive care than were people with no such history. This elevated risk of severe illness was on par with that from smoking.

“There’s this sense among the public that cannabis is safe to use, that it’s not as bad for your health as smoking or drinking, that it may even be good for you,” said senior author Li-Shiun Chen, MD, DSc, a professor of psychiatry. “I think that’s because there hasn’t been as much research on the health effects of cannabis as compared to tobacco or alcohol. What we found is that cannabis use is not harmless in the context of COVID. People who reported yes to current cannabis use, at any frequency, were more likely to require hospitalisation and intensive care than those who did not use cannabis.”

Cannabis use was different than tobacco smoking in one key outcome measure: survival. While smokers were significantly more likely to die of COVID than nonsmokers, a finding that fits with numerous other studies, the same was not true of cannabis users, the study showed.

“The independent effect of cannabis is similar to the independent effect of tobacco regarding the risk of hospitalisation and intensive care,” Chen said. “For the risk of death, tobacco risk is clear but more evidence is needed for cannabis.”

The study analysed deidentified electronic health records of people who were seen for COVID at BJC HealthCare hospitals and clinics in Missouri and Illinois between Feb. 1, 2020, and Jan. 31, 2022. The records contained data on demographic characteristics such as sex, age and race; other medical conditions such as diabetes and heart disease; use of substances including tobacco, alcohol, cannabis and vaping; and outcomes of the illness: specifically, hospitalisation, intensive-care unit (ICU) admittance and survival.

COVID patients who reported that they had used cannabis in the previous year were 80% more likely to be hospitalised and 27% more likely to be admitted to the ICU than patients who had not used cannabis, after taking into account tobacco smoking, vaccination, other health conditions, date of diagnosis, and demographic factors. For comparison, tobacco smokers with COVID9 were 72% more likely to be hospitalized and 22% more likely to require intensive care than were nonsmokers, after adjusting for other factors.

These results contradict some other research suggesting that cannabis may help the body fight off viral diseases such as COVID.

“Most of the evidence suggesting that cannabis is good for you comes from studies in cells or animals,” Chen said. “The advantage of our study is that it is in people and uses real-world health-care data collected across multiple sites over an extended time period. All the outcomes were verified: hospitalisation, ICU stay, death. Using this data set, we were able to confirm the well-established effects of smoking, which suggests that the data are reliable.”

The study was not designed to answer the question of why cannabis use might make COVID worse. One possibility is that inhaling marijuana smoke injures delicate lung tissue and makes it more vulnerable to infection, in much the same way that tobacco smoke causes lung damage that puts people at risk of pneumonia, the researchers said. That isn’t to say that taking edibles would be safer than smoking joints. It is also possible that cannabis, which is known to suppress the immune system, undermines the body’s ability to fight off viral infections no matter how it is consumed, the researchers noted.

“We just don’t know whether edibles are safer,” said first author Nicholas Griffith, MD, a medical resident at Washington University. Griffith was a medical student at Washington University when he led the study. “People were asked a yes-or-no question: ‘Have you used cannabis in the past year?’ That gave us enough information to establish that if you use cannabis, your health-care journey will be different, but we can’t know how much cannabis you have to use, or whether it makes a difference whether you smoke it or eat edibles. Those are questions we’d really like the answers to. I hope this study opens the door to more research on the health effects of cannabis.”

Source: Washington University in St. Louis

Categories : COVID GeneticsTags :

Key Gene may Protect Against Severe COVID Infections in Men Under 75

On By ModernMedia
Photo: CC0

A certain variant of a key anti-inflammatory gene protects men under age 75 from severe illness and death when hospitalised from COVID, a genetic analysis of their blood shows. According to the authors of a major study published in The Journal of Infectious Diseases, the protective gene in question, an interleukin-1 receptor antagonist (IL1RN) variant, appears to tamp down inflammation, which can get out of control in severe cases SARS-CoV-2 infection.

The study showed that 124 men between the ages of 19 and 74 who possessed the IL1RN variant, called rs419598, were less likely to become severely ill after hospitalisation for COVID, and 80% less likely to die from the disease.

IL1RN is expressed naturally in the body. Different types of interleukin genes are known to dial inflammation up or down in the context of arthritis, and researchers say the results of the current study suggest that a similar dynamic influences the interleukin-1-related inflammation seen in COVID patients.

The findings, from researchers at NYU Grossman School of Medicine, stand out because historically more men than women are known to die from COVID, and the IL1RN rs419598 variant appears to selectively protect only men up to age 74, but not beyond that as age-related chronic illnesses unfold.

The research team used sequencing technologies for the study to determine the presence of specific genes or variations in the letter code that makes up genes in blood samples from 2589 men and women hospitalised for COVID at NYU Langone’s Tisch Hospital in Manhattan from March 2020 to March 2021.

More than half of the men and women in the study were older than age 60 and obese, factors that are known to increase the risk of death from the viral infection. Overall, more men than women (240 men, at 60.5%; and 157 women, at 39.5%) died from their disease, with women 20% less likely to die than men.

“Our study results show that among hospitalised patients, while women are still overall less likely than men to die from COVID-19, those men age 74 and younger who possess the IL1RN gene variant rs419598 are much less likely to suffer the severe inflammation tied to SARS-CoV-2 infection and less likely to die from the disease,” said study colead investigator and molecular biologist Mukundan Attur, PhD. Attur is an associate professor in the Department of Medicine at NYU Langone Health.

Among the study’s other findings was that average blood levels of the anti-inflammatory protein IL-1Ra, coded by IL1RN, were 14 times higher in 181 hospitalised men than in healthy male study controls from the general population, and 10 times as high in 178 hospitalised women than in healthy females. The increased levels of IL-1Ra in women did not result in any statistically significant mortality reductions.

“Our analysis offers substantial evidence of the biological link between the severe inflammation seen in SARS-CoV-2 and that which occurs in rheumatoid arthritis,” said study senior investigator Steven Abramson, MD, the Frederick H. King Professor of Internal Medicine at NYU Langone.

Abramson, a rheumatologist who also serves as chair of the Department of Medicine and chief academic officer at NYU Langone, says previous research has shown that such rheumatoid inflammation is lower in people who possessed one of the three IL1RN variants analysed in the study.

More importantly, Abramson says, the new research suggests that restraining the interleukin-1 biological pathway, which is in part tamped down by the anti-inflammatory protein IL-1Ra, could help prevent the severe inflammation seen in SARS-CoV-2 infection. Further research, he says, is warranted into whether IL-1-inhibiting therapies, such as the IL1 receptor antagonists anakinra, canakinumab, and rilonacept, are effective against Covid infection.

Abramson already has plans to investigate if the IL-1 pathway plays a role in long Covid, when people experience new or lingering symptoms, such as fatigue and ‘brain fog’, months after recuperating from their initial infection.

Abramson points out that the new study adds to the growing scientific evidence about the biological factors that contribute to gender differences seen in deaths from COVID, which are known to vary widely across the United States.

Source: NYU Langone Health / NYU Grossman School of Medicine

Categories : Metabolic Disorders Respiratory DiseasesTags :

Why People with Diabetes are More Vulnerable to Respiratory Infection

On By ModernMedia
Credit: Scientific Animations CC4.0

It has long been known that people with diabetes are at a substantially increased risk of developing severe lung disease if they become infected with viruses such as influenza, as well as other pathogens. When the COVID-19 pandemic started in early 2020, it became even more important to understand this mysterious phenomenon. It became clear that people with diabetes were at a significantly higher risk of coming down with severe, even fatal, lung disease after developing severe COVID, but no one understood why. In fact, some 35% of the pandemic’s COVID mortalities had diabetes.

Now, research conducted at the Weizmann Institute of Science and published in Nature has revealed how, in diabetics, high levels of blood sugar disrupt the function of key cell subsets in the lungs that regulate the immune response. It also identifies a potential strategy for reversing this susceptibility and saving lives.

Prof. Eran Elinav‘s team in his lab at Weizmann, headed by Drs. Samuel Nobs, Aleksandra Kolodziejczyk and Suhaib K. Abdeen, subjected multiple mouse models of types 1 and 2 diabetes to a variety of viral lung infections. Just as in diabetic humans, in all these models the diabetic mice developed a severe, fatal lung infection following exposure to lung pathogens such as influenza. The immune reaction, which in nondiabetics eliminates the infection and drives tissue healing, was severely impaired in the diabetic mice, leading to uncontrolled infection, lung damage and eventual death.

Next, to decode the basis of this heightened risk, the team performed an evaluation of gene expression on the level of individual cells, in more than 150 000 single lung cells of infected diabetic and nondiabetic mice. The researchers also performed an extensive array of experiments involving immune and metabolic mechanisms, as well as an in-depth assessment of immune cell gene expression in infected diabetic mice. In the diabetic mice they identified a dysfunction of certain lung dendritic cells, the immune cells that orchestrate a targeted immune response against pathogenic infection. “High blood sugar levels severely disrupt certain subsets of dendritic cells in the lung, preventing these gatekeepers from sending the molecular messages that activate the critically important immune response,” says Nobs, postdoctoral fellow and study first author. “As a result, the infection rages on, uncontrolled.”

Next, they explored ways to prevent the harmful effects of hyperglycaemia in lung dendritic cells, as a means of lowering the infection’s risk in diabetic animals. Indeed, tight control of glycaemic levels by insulin supplementation prompted the dendritic cells to regain their capacity to generate a protective immune response that could prevent the cascade of events leading to a severe, life-threatening viral lung infection. Alternatively, administration of small molecules reversing the sugar-induced regulatory impairment corrected the dendritic cells’ dysfunction and enabled them to generate a protective immune response despite the presence of hyperglycaemia.

“Correcting blood sugar levels, or using drugs to reverse the gene regulatory impairment induced by high sugar, enabled our team to get the dendritic cells’ function back to normal,” says Abdeen, a senior intern who co-supervised the study. “This was very exciting because it means that it might be possible to block diabetes-induced susceptibility to viral lung infections and their devastating consequences.”

Lung tissue of a diabetic mouse (right) contains fewer immune cells (small purple dots) than that of a non-diabetic animal (left)

With over 500 million people around the world affected by diabetes, and with diabetes incidence expected to rise over the next decades, the new research has significant, promising clinical implications.

“Our findings provide, for the first time, an explanation as to why diabetics are more susceptible to respiratory infection,” Elinav says. “Controlling sugar levels may make it possible to reduce this pronounced diabetes-associated risk. In diabetic patients whose sugar levels are not easily normalized, small molecule drugs may correct the gene alterations caused by high sugar levels, potentially alleviating or even preventing severe lung infection. Local administration of such treatments by inhalation may minimize adverse effects while enhancing effectiveness, and merits future human clinical testing.”

Source: Weizmann Institute of Science

Categories : COVIDTags :

Which Entryway a Coronavirus Uses Affects its Infection Severity

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Until now, the reason why some coronaviruses such as SARS-CoV-2 affect humans more severely than other seasonal ones has eluded scientists. Now, results published in Nature have provided a piece of the puzzle by identifying a gateway used by the seasonal coronavirus HKU1 to enter human cells. HKU1 binds to a different receptor than SARS-CoV-2, which may partly explain the difference in severity between these two coronaviruses.

Receptors provide a useful means of figuring out coronavirus transmissibility and pathology as part of surveillance work on viral evolution. Seven coronaviruses are known for their ability to infect humans. Four of these are generally mild: HKU1, 229E, NL63 and OC43, while the other three are more pathogenic: SARS-CoV-1, Mers-CoV and SARS-CoV-2.

The HKU1 virus was first identified in an elderly patient with severe pneumonia in Hong Kong in 2005. Like SARS-CoV-2, HKU1 mainly infects upper respiratory tract cells. However, it rarely affects the bronchi and alveoli in the lungs. The HKU1 virus causes colds and other mild respiratory symptoms. Complications may also occur, including severe respiratory tract infections, particularly in young children, the elderly and immunocompromised individuals. It is estimated that 70% of children are infected before the age of 6. In total, 75 to 95% of the global population has been exposed to HKU1, which is comparable to other seasonal human coronaviruses.

At the cellular level, coronavirus spike proteins are cleaved after binding to their receptors. This cleavage phenomenon is vital for viral fusion, entry and multiplication. Some coronaviruses (SARS-CoV-2 and NL63) use the ACE2 receptor as a gateway for entering cells. Until now, HKU1 and OC43 were the only coronaviruses with unknown receptors.

Through collaboration between scientists at eight Institut Pasteur units, it was possible to identify the TMPRSS2 enzyme as the receptor to which HKU1 binds to enter cells. Once binding has occurred, TMPRSS2 triggers fusion of HKU1 with the cell, leading to viral infection. Through a combination of techniques performed in vitro and in cell culture, the scientists demonstrated that the TMPRSS2 receptor has high affinity with the HKU1 spike, which is not the case for SARS-CoV-2.

“Once a receptor has been identified for a virus, it is possible to characterise target cells more accurately, while also gaining insights on viral entry and multiplication mechanisms and infection pathophysiology,” comments, Olivier Schwartz, co-last author of the study and Head of the Institut Pasteur’s Virus and Immunity unit.

“Our findings also shed light on the various evolution strategies employed by coronaviruses, which use TMPRSS2 either to bind to target cells or trigger fusion and viral entry,” adds Julian Buchrieser, co-last author of the study and scientist in the Institut Pasteur’s Virus and Immunity unit.

These human-pathogenic viruses’ use of different receptors probably affects their degree of severity. Receptor levels vary among respiratory tract cells, thus influencing the sensitivity of cells to infection and viral spread. Once the route of viral entry into cells is known, it should also be possible to fight infection more effectively by developing targeted therapies and assess the risk of virulence posed by any future emerging coronaviruses.

In parallel with this work, Institut Pasteur teams led by Pierre Lafaye and Felix Rey have developed and characterised nano-antibodies (very small antibodies) that inhibit HKU1 infection by binding to the TMPRSS2 receptor. These reagents have been patented for potential therapeutic activities.

Source: Institut Pasteur

Categories : Gender LungTags :

Why Many Lung Diseases are Sex-biased

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Anatomical model of lungs
Photo by Robina Weermeijer on Unsplash

By studying sex differences in expression across more than 2500 genes in mouse lung cells, researchers may have found an explanation for sex biases in the prevalence and severity of lung diseases, such as the greater severity of COVID for males. In particular, very high numbers of X-linked genes escape transcriptional silencing in lung alveolar type 2 (AT2s) cells, according to their study published in Stem Cell Reports.

“Our study is the first to compare male and female AT2 cells for gene expression, and our findings suggest that there are likely sex differences in lung repair following viral-induced injury,” says co-senior author Montserrat Anguera, an associate professor at the University of Pennsylvania.

Sex differences exist for many lung diseases, but the mechanistic basis for this remains unclear. “We started this project during the beginning of the pandemic, because we were curious about the sex bias with COVID disease, where more older men have increased morbidity, and wondered whether X-chromosome inactivation (XCI) might contribute to this sex bias,” Anguera says. “We realised that the SARS-CoV2 virus first encounters AT2 cells in the lung, and that the virus enters cells through the angiotensin-converting enzyme 2 (Ace2) receptor, which is located on the X chromosome.”

XCI is a process by which one of the copies of the X chromosome is inactivated in female mammals. The inactive X chromosome is silenced by being packaged into a transcriptionally inactive structure called heterochromatin. XCI prevents female mammals from having twice as many X-chromosome gene products as males, who only possess a single copy of the X chromosome.

In the new study, Anguera and co-senior author Andrew Vaughan, an assistant professor at the University of Pennsylvania, investigated XCI maintenance and sex-specific gene expression profiles using male and female AT2s. The results showed that approximately 68% of expressed X-linked genes in mouse AT2s escape XCI. These genes include Ace2, which serves as the entry point into cells for SARS-CoV-2, but is also involved in lung repair.

There were genome-wide expression differences between male and female AT2s, possibly contributing to sex differences in lung injury and repair in multiple settings. Taken together, the findings demonstrate that AT2 cells have the highest levels of XCI escape for mouse cells reported to date and support a renewed focus on AT2s as a potential contributor to sex-biased differences in lung disease.

In addition, the results showed that AT2 cells, similar to immune cells, do not strictly follow the classic rules of XCI. “We were surprised to find that female AT2 cells lack canonical epigenetic modifications that are typically enriched on the inactive X as a result of XCI. These include the long noncoding RNA Xist and heterochromatic histone modifications H3K27me3 and H2AK119-ubiquitin,” Anguera says. “Because the inactive X in female AT2 cells has fewer epigenetic marks, this enables more gene expression chromosome wide, including the Ace2 gene.”

For now, it remains an open question whether ACE2 escapes XCI in human AT2 cells. to The authors say this is a likely scenario because there are significantly higher numbers of XCI escape genes in human cells compared to mouse cells.

Moving forward, the authors plan to investigate how expression from the inactive X in AT2 cells is affected by SARS-CoV2 infections. They also will continue to study how expression from the X chromosome is regulated in other cell types that do not exhibit conventional XCI maintenance. “Our findings open the door to future work investigating the genetic and epigenetic basis, residing within the X chromosome, of sex differences in immune responses to inhaled viruses,” Anguera says.

Source: Science Daily

Categories : COVID GenderTags :

Low Testosterone may be a Risk Factor for Severe COVID

On By ModernMedia
Testosterone molecule
Model of a testosterone molecule. Source: Wikimedia CC0

Among men with COVID, those with low testosterone levels are more likely to become seriously ill and be hospitalised than men with normal levels of the hormone, according to a study which appears in JAMA Network Open.

Analysis of data for 723 men who tested positive for COVID, mostly in 2020 before vaccines were available, indicated that low testosterone is an independent risk factor for COVID hospitalisation, similar to diabetes, heart disease and chronic lung disease.

They found that men with low testosterone who developed COVID were 2.4 times more likely to require hospitalisation than men with hormone levels in the normal range. Further, men who were once diagnosed with low testosterone but successfully treated with hormone replacement therapy were no more likely to be hospitalised for COVID than men whose testosterone levels had always tested in the normal range.

The findings, by researchers from the Washington University School of Medicine in St. Louis and Saint Louis University School of Medicine, suggest that treating men with low testosterone may help protect them against severe disease and reduce the burden on hospitals during COVID waves.

“It is very likely that COVID is here to stay,” said co-senior author Abhinav Diwan, MD, a professor of medicine at Washington University. “Hospitalizations with COVID are still a problem and will continue to be a problem because the virus keeps evolving new variants that escape immunization-based immunity. Low testosterone is very common; up to a third of men over 30 have it. Our study draws attention to this important risk factor and the need to address it as a strategy to lower hospitalisations.”

Prof Diwan and co-senior author Sandeep Dhindsa, MD, an endocrinologist at Saint Louis University, had previously shown that men hospitalised with COVID have abnormally low testosterone levels. However, severe illness or traumatic injury can cause a temporary drop in hormone levels, so causation cannot be proved in data from men already hospitalised with COVID. Data were needed for men with chronically low testosterone before COVID infection.

Profs Diwan, Dhindsa and colleagues identified 723 men whose testosterone levels had been measured between Jan. 1, 2017, and Dec. 31, 2021, and who had documented cases of COVID in 2020 or 2021. In some cases, testosterone levels were measured after the patient recovered from COVID. Since low testosterone is a chronic condition, men who tested low a few months after recovering from COVID probably had low levels before as well, Prof Dhindsa said.

The researchers identified 427 men with normal testosterone levels, 116 with low levels, and 180 who previously had low levels but were being successfully treated, meaning that they were on hormone replacement therapy and their testosterone levels were in the normal range at the time they developed COVID.

“Low testosterone turned out to be a risk factor for hospitalisation from COVID, and treatment of low testosterone helped to negate that risk,” Prof Dhindsa said. “The risk really takes off below a level of 200 nanograms per decilitre, with the normal range being 300 to 1000 nanograms per decilitre. This is independent of all other risk factors that we looked at: age, obesity or other health conditions. But those people who were on therapy, their risk was normal.”

Men with low testosterone levels can experience sexual dysfunction, depressed mood, irritability, difficulty with concentration and memory, fatigue, loss of muscular strength and a reduced sense of well-being overall. When a man’s quality of life is clearly diminished, he is typically treated with testosterone replacement therapy. When the symptoms are mild, though, doctors and patients may hesitate to treat.

The two main concerns related to testosterone therapy are an increased risk of prostate cancer and heart disease. Testosterone is well known to boost prostate cancer, but for heart disease, the evidence for risk is more ambiguous. A large clinical trial on the relationship between heart health and testosterone supplementation is expected to be completed soon.

“In the meantime, our study would suggest that it would be prudent to look at testosterone levels, especially in people who have symptoms of low testosterone, and then individualise care,” said Prof Diwan, whose specialty is cardiology. “If they are at really high risk of cardiovascular events, then the doctor could engage the patient in a discussion of the pros and cons of hormone replacement therapy, and perhaps lowering the risk of COVID hospitalisation could be on the list of potential benefits.”

Since this study is observational, it only suggests that boosting testosterone levels may help men avoid severe COVID, Diwan cautioned. A clinical trial would be needed to demonstrate conclusively whether such a strategy works.

Source: Washington University School of Medicine

Categories : COVIDTags :

SA Study Finds no Increased Severity in Omicron BA.4 and BA.5 Infections

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South African researchers have found that, compared to Omicron BA.1 and earlier infections, those caused by Omicron BA.4 and BA.5 do not have an increased risk of hospitalisation for severe disease or death.

The study, which appears online in the medRxiv server, aimed to compare clinical severity of Omicron BA.4/BA.5 infection with BA.1 and earlier variant infections among laboratory-confirmed SARS-CoV-2 cases in the Western Cape, South Africa, using timing of infection to infer the lineage/variant causing infection.

In their study, the researchers included public sector patients aged 20 years or older with laboratory-confirmed COVID between 1 and 21 May 2022 (for the BA.4/BA.5 wave) and equivalent prior wave periods. They compared the risk for death and severe hospitalisation/death (all within 21 days of diagnosis), adjusting for for demographics, comorbidities, admission pressure, vaccination and prior infection.

Comparing 3793 patients from the BA.4/BA.5 wave and 190 836 patients from previous waves the risk of severe hospitalisation or death was similar in the BA.4/BA.5 and BA.1 waves (adjusted hazard ratio [aHR] 1.12). Both Omicron waves had a lower risk of severe outcomes than previous waves. They also found that both prior infection (aHR 0.29) and vaccination (aHR 0.17; 0.40 for boosted vs no vaccine) were protective.

Overall, the researchers found that COVID disease severity was similar for the BA.4/BA.5 and BA.1 periods in the context of growing immunity against SARS-CoV-2 due to prior infection and vaccination, which were both strongly protective.