Tag: Omicron

Categories : COVID Immune SystemTags :

COVID did not get Weaker – Our Immune Systems got Stronger, Large Scale Study Suggests

On By ModernMedia
Image by Fusion Medical on Unsplash

Researchers have shown that the reduced mortality from COVID is not necessarily due to the fact that later variants, such as Omicron, have been less severe. Rather, the reduced mortality seems to be due to several other factors, such as immunity from previous vaccinations and previous infections. The study is published in the latest issue of Lancet Regional Health Europe.

The researchers at Karolinska Institutet, together with partners in the EuCARE project, conducted a study using patient data from more than 38 500 hospitalised patients with COVID, from the start of the pandemic to October 2022. The data comes from hospitals in ten countries, including two outside Europe.

The data showed that in-hospital mortality decreased as the pandemic progressed, especially since Omicron became the dominant variant. However, when the researchers modelled the mortality rates for different variants (pre-Alpha, Alpha, Delta and Omicron) and took into account factors such as age, gender, comorbidity, vaccination status and time period, they saw far fewer differences and weaker associations. They also saw differences between age groups, highlighting the importance of conducting separate analyses for different age groups. 

“Overall, our findings suggest that the observed reduction in mortality during the pandemic is due to multiple factors such as immunity from vaccination and previous infections, and not necessarily tangible differences in inherent severity,” says Pontus Hedberg, first author of the study. 

Omicron variant no less severe 

Understanding the disease course and outcomes of patients hospitalised with COVID during the pandemic is important to guide clinical practice and to understand and plan future resource use for COVID. A particularly interesting finding is that the inherent severity of Omicron has not necessarily been significantly reduced, but that other factors are behind the reduction in mortality. 

“The fact that Omicron can cause severe disease was seen in Hong Kong, for example, where the population had low immunity from previous infections and low vaccination coverage. In Hong Kong there was a relatively high mortality from Omicron,” says Pontus Hedberg. 

Highlights the importance of protecting the elderly and those with underlying diseases

The main applications of the study results going forward are the continued need to protect the elderly and patients with other underlying disease from severe disease outcomes through vaccination against COVID, even though new virus variants may appear less virulent. The results are also important for understanding trends in mortality in hospitalised patients with COVID and thus planning for resource use in hospital care.

Larger multinational collaborative projects like this are of great value to increase the generalisability of studies and not least to promote international collaboration also for future pandemic or epidemic scenarios.

Source: Karolinska Institutet

Categories : COVID UncategorizedTags :

Omicron-derived Immunity Protects Less against Other Variants

On By ModernMedia
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In unvaccinated individuals, omicron-derived immunity provides little long-term immunity against other variants, according to new research in the journal Nature.

In experiments using mice and blood samples from omicron-infected, the team found that the omicron variant induces only a weak immune response. In vaccinated individuals, this weak response helped strengthen overall protection against a variety of COVID strains. In contrast, the immune response in unvaccinated individuals failed to confer broad, robust protection against other strains.

“In the unvaccinated population, an infection with omicron might be roughly equivalent to getting one shot of a vaccine,” said Melanie Ott, MD, PhD, director of the Gladstone Institute of Virology and co-senior author of the new work. “It confers a little bit of protection against COVID, but it’s not very broad.”

A weaker infection

When it emerged in late 2021, omicron infection was soon observed to cause less severe disease, but whether it conferred broad, long-term immunity was not known.

“When the omicron variant first emerged, a lot of people wondered whether it could essentially act as a vaccine for people who didn’t want to get vaccinated, eliciting a strong and broad-acting immune response,” said Irene Chen, co-first author of the new study and graduate student in Ott’s lab.

To find the answer, the team of researchers first examined the effect of omicron in mice. In the omicron-infected mice, despite the milder symptoms, the immune system still generated the T cells and antibodies typically seen in response to other viruses.

“We demonstrated in this study that the lower pathogenicity of omicron is not because the virus cannot take hold,” said Nadia Roan, PhD, an associate investigator at Gladstone.

This means the difference in symptoms and immune response due to other reasons, such as lower replication or the type of antibodies that are generated.

No cross-variant protection

The researchers took blood samples from mice infected with the ancestral, delta, or omicron variants of SARS-CoV-2 and measured the ability of their immune cells and antibodies to recognise five different viral variants – ancestral (WA1), alpha, beta, delta, and omicron.

Blood from uninfected animals was unable to neutralise any of the viruses. Samples from WA1-infected animals could neutralise alpha and, to a lesser degree, the beta and delta virus – but not omicron. Samples from delta-infected mice could neutralise delta, alpha and, to a lesser degree, the omicron and beta virus.

Blood from omicron-infected mice could only neutralise the omicron variant.

The team confirmed these results using blood from ten unvaccinated people who had been infected with omicron, and found their blood was unable to neutralise other variants. When they tested blood from 11 unvaccinated people who had been infected with delta, the samples could neutralise delta and, as had been seen in mice, the other variants to a lesser extent.

When they repeated the experiments with blood from vaccinated people, the results were different: vaccinated individuals with confirmed omicron or delta breakthrough infections all showed the ability to neutralize all the tested variants, conferring higher protection.

“When it comes to other variants that might evolve in the future, we can’t predict exactly what would happen, but based on these results, I’d suspect that unvaccinated people who were infected with omicron will have very little protection,” said Ott. “But on the contrary, vaccinated individuals are likely to be more broadly protected against future variants, especially if they had a breakthrough infection.”

Categories : COVIDTags :

Why Omicron May Hit Other Countries Harder

On By ModernMedia
COVID heat map. Photo by Giacomo Carra on Unsplash

South Africa may have gotten off more lightly from Omicron due to widespread immunity from previous infection combined with vaccine coverage, researchers think, which may not bode well for other countries which have not completed their vaccination nor seen the worst COVID surges.

The South African Medical Research Council in collaboration with Discovery Health on Tuesday last week presented data from a large study showing  that South Africans infected with Omicron are, on average, less likely to be hospitalised, and recover faster, compared to the other variants.

Their study looked at more than 200 000 COVID cases in South Africa during a Delta-driven surge in September and October, and the start of the Omicron-driven surge in November, as that variant began increasing rapidly. About a quarter of the people in the study already have a chronic illness, putting them at higher risk of severe COVID.

The researchers found a hopeful trend: The risk of hospitalisation for adults dropped 30% during the early days of the Omicron surge from the levels seen there in September and October.

“The hospital admissions during omicron, standing at 58 per 1000 infections, are the lowest of the four COVID waves, and one-third of what we experienced during the delta surge,” said Discovery Health CEO Ryan Noach.

Why was this so? One explanation could be the immunity from COVID recovery present in the population. South Africa had experienced three huge COVID surges with low vaccination rates compared to the US and Europe.

When the Omicron variant appeared, only about a quarter of the population were vaccinated but the vast majority of residents had likely already been infected with previous variants of SARS-CoV-2. This was based on the excess mortality rate observed in the country through the pandemic, and so it is thought that South Africans likely had some immunity granted by infection.

“Thus, Omicron enters a South African population with considerably more immunity than any prior SARS-CoV-2 variant,” concluded Dr Roby Bhattacharyya, an infectious disease specialist, and epidemiologist William Hanage in a recent working paper. This means that most Omicron cases are likely to be reinfections, rather than first infections.
Other countries will not have as broad a ‘coverage’ of vaccination and previous infection as South Africa. Around 125 million Americans are unvaccinated, and a recent study estimated that about 20% of Americans had been infected with COVID from the start of the pandemic, up to August, 2021.

The data therefore suggest that a minimum of 20% of Americans who are completely ‘naive’, as scientists term it, when it comes to exposure to SARS-CoV-2.

Source: NPR

Categories : COVIDTags :

Real-world Data Shows Booster Shot Protective against Omicron

On By ModernMedia
Photo by Mat Napo on Unsplash

While two doses of a COVID vaccine offered less protection against Omicron, a booster shot restored immunity back to high levels, according to real-world data from the UK.

Two doses of Pfizer vaccine provided just under 40% protection against symptomatic infection with the Omicron variant about 25 weeks after the second dose compared with around 60% protection against Delta, according to a technical briefing released by the UK Health Security Agency. [PDF]

“These early estimates suggest that vaccine effectiveness against symptomatic disease with the Omicron variant is significantly lower than compared to the Delta variant,” the agency noted in the report. However, “moderate to high” vaccine effectiveness was observed in the early period after a booster shot, they added.

The agency found that a Pfizer booster increased vaccine effectiveness to 76%. Among people who received the AstraZeneca series for their initial immunisation (which offered almost no protection against Omicron), vaccine effectiveness jumped to 71% after a Pfizer booster.

The reportcompared vaccine effectiveness against Omicron versus Delta, including 581 people who were infected with the new strain and more than 56 000 infected with Delta from the end of November to December 6.

Omicron’s reinfection rate was also much higher than Delta’s. Of 329 individuals infected with Omicron, 7% had a previous infection, compared with 0.4% of the approximately 85 000 people infected with Delta.

After adjustments for age and area, the risk ratio of reinfection for Omicron was 5.2 (95% CI 3.4-7.6).

The report also found a 20- to 40-fold reduction in neutralising antibody activity compared with the viruses used to develop the vaccines. However, a booster dose significantly improved neutralising antibodies, regardless of which vaccine was given in the initial immunisation.

Katelyn Jetelina, PhD, an epidemiologist at the University of Texas Health Science Center at Houston, said that the study data confirm what researchers have already discovered in lab research: vaccines offer significantly less protection against Omicron, and reinfection rates are expected to be high.

Dr Jetelina noted that it was reassuring to see that “we can curb infection still with a booster, which is really quite phenomenal.” However, she said that cases were likely to increase.

“I think all this data is showing us that we’re going to have a lot of infections with Omicron,” Jetelina told MedPage Today. While a high rate of infection does not necessarily translate to severe illness, Dr Jetelina said that she is concerned about population-level outcomes resulting from a flood of new cases.

“That’s where I get a bit more nervous,” she said. She pointed out that “even if the rate of severe disease is low […] those numbers start adding up real quickly.”

The UK Health Security Agency advised interpreting the results with caution, due to the low number of Omicron cases. Additionally, more data are needed before scientists can determine how well vaccines will work against severe illness, hospitalisation, and death from the Omicron strain.

“It will be a few weeks before effectiveness against severe disease with Omicron can be estimated,” the agency stated. “However, based on this experience, this is likely to be substantially higher than the estimates against symptomatic disease.”

Source: MedPage Today

Categories : COVID HospitalsTags : 1 Comment

Netcare Reports Less Severe COVID in Fourth Wave

On By ModernMedia
Image by Quicknews

In a news release by Netcare, the company’s CEO Dr Richard Friedland said that more than three weeks after the discovery of the new Omicron variant in South Africa, data across its hospitals and primary healthcare facilities are demonstrating important early trends.

“Having personally seen many of our patients across our Gauteng hospitals, their symptoms are far milder than anything we experienced during the first three waves,” commented Dr Friedland.

“Approximately 90% of COVID patients currently in our hospitals require no form of oxygen therapy and are considered incidental cases. While we fully recognise that it is still early days, if this trend continues, it would appear that with a few exceptions of those requiring tertiary care, the fourth wave can be adequately treated at a primary care level.”

Rates of community transmission and hospital admission possibly decoupled
During the first three waves, the rate of hospital admissions rose in tandem with the rate of community transmission (the number of people testing positive). Dr Friedland noted that, in the first three waves of the pandemic, Netcare treated 126 000 COVID patients across its 49 acute hospitals, of which 55 000 (44%) patients required admission and 26% of these patients were treated in High Care and Intensive Care (ICU). Significantly, all COVID patients admitted were sick and required some form of oxygen therapy. The high admission rate, as well as the high percentage of patients requiring ICU or High Care indicates the severity of cases during the first three waves.

“As of today we have 337 COVID positive patients admitted (72% in the Gauteng area and 18% in KwaZulu-Natal). Of these patients approximately 10% (33 patients) are on some form of oxygenation versus 100% in the first three waves. Eight of these patients (2%) are being ventilated and of these, two are primary trauma cases that are also COVID positive.”

Netcare’s policy is to test all patients for COVID before or on admission. Patients admitted for other primary diagnoses or surgical procedures who test positive for COVID] but do not require any form of oxygenation are considered to be incidental COVID cases, which currently accounts for 90% of COVID cases now in Netcare hospitals.

“During the first three waves, when the overall community positivity rate breached 26% across South Africa, we were inundated with COVID admissions to hospital. Within Netcare we had over 2000 COVID patients in hospitals during the first wave, over 2 250 patients in hospital during the second wave and over 3000 patients in hospital during the third wave. At present the 337 patients represent a fraction compared to previous waves,” said Dr Friedland.

“The very rapid rise in community transmission as compared to previous waves may partially explain this relatively low hospital admission rate. However, there does appear to be a decoupling in terms of the rate of hospital admissions at this early stage in the evolution of the fourth wave,” suggested Dr Friedland.

Majority of patients unvaccinated
Dr Friedland added that of a total of 800 COVID positive patients that were admitted since 15 November, 75% of patients were unvaccinated. Netcare has seen seven deaths over this period in this group of patients, of which four may be ascribed to COVID. These four patients were 58 to 91 years of age and had significant co-morbidities. Of these patients, three were not vaccinated.

Dr Friedland observed that COVID patients admitted since 15 November are on average younger than those seen during the first three waves. Over 71% are under 50, with an average age of 38.5. This compares to only 40% below 50 in the first three waves, with an average age of 54.

Virtually all patients have presented with mild to moderate flu-like symptoms, including a blocked or runny nose, headache and a scratchy or sore throat and have been treated symptomatically.

Dr Friedland reiterated that the best way to support South Africa remains to take COVID extremely seriously and to be as cautious as ever.