A Lancet study finds that natural immunity against severe COVID-19 is strong and long-lasting for all variants in previously infected individuals. However, protection against Omicron BA.1 reinfection is reduced for those with past pre-Omicron infections. Researchers stress that vaccination is still the safest way to acquire immunity.
- Largest review and meta-analysis assessing the extent of protection following COVID-19 infection by variant and how durable that protection is against different variants, including 65 studies from 19 countries.
- For people who have been infected with COVID-19 at least once before, natural immunity against severe disease (hospitalization and death) was strong and long-lasting for all variants (88% or greater at 10 months post-infection).
- Past infection with pre-Omicron variants provided substantially reduced natural immunity protection against reinfection with Omicron BA.1 (36% at 10 months after infection).
- The researchers say we should recognize the natural immunity in people who have recently been infected with COVID-19, but warn that their findings should not discourage vaccination because it is the safest way to acquire immunity.
For someone previously infected with COVID-19, their risk of hospitalization or death is 88% lower for at least 10 months compared to those who had not been previously infected, according to a systematic review and meta-analysis published in The Lancet.
The analysis also suggests that the level and duration of protection against reinfection, symptomatic disease, and severe illness is at least on a par with that provided by two doses of the mRNA vaccines (Moderna, Pfizer-BioNtech) for ancestral, Alpha, Delta, and Omicron BA.1 variants. The study did not include data on infection from Omicron XBB and its sublineages.
As IHME co-author Dr. Caroline Stein explains: “Vaccines continue to be important for everyone in order to protect high-risk populations such as those who are over 60 years of age and those with comorbidities. This also includes populations that have not previously been infected and unvaccinated groups, as well as those who were infected or received their last vaccine dose more than six months ago. Decision makers should take both natural immunity and vaccination status into consideration to obtain a full picture of an individual’s immunity profile.”
Since January 2021, several studies and reviews have reported the effectiveness of past COVID-19 infection in reducing the risk of reinfection and how immunity wanes over time. But none has comprehensively assessed how long the protection after natural infection will last and how durable that protection will be against different variants.
To provide more evidence, the researchers conducted a review and meta-analysis of all previous studies that compared the reduction in risk of COVID-19 among non-vaccinated individuals against a SARS-CoV-2 reinfection to non-vaccinated individuals without a previous infection up to September 2022.
It included 65 studies from 19 countries (Austria, Belgium, Brazil, Canada, Czechia, Denmark, France, India, Italy, Netherlands, Nicaragua, Norway, Qatar, Scotland, South Africa, Sweden, Switzerland, the UK, and the USA) and evaluates the effectiveness of past infection by outcome (infection, symptomatic disease, and severe disease), variant, and time since infection. Studies examining natural immunity in combination with vaccination (i.e., hybrid immunity) were excluded from the analyses.
Immunity fades over time
Analysis of data from 21 studies reporting on time since infection from a pre-Omicron variant estimated that protection against reinfection from a pre-Omicron variant was about 85% at one month—and this fell to about 79% at 10 months. Protection from a pre-Omicron variant infection against reinfection from the Omicron BA.1 variant was lower (74% at one month) and declined more rapidly to 36% at around 10 months.
Nevertheless, analysis of five studies reporting on severe disease (hospitalization and death) found that protection remained universally high for 10 months: 90% for ancestral, Alpha, and Delta, and 88% for Omicron BA.1.
Six studies evaluating protection against Omicron sub-lineages specifically (BA.2 and BA.4/BA.5) suggested significantly reduced protection when the prior infection was pre-Omicron variant. But when the past infection was Omicron, protection was maintained at a higher level.
“The weaker cross-variant immunity with the Omicron variant and its sub-lineages reflects the mutations they have that make them escape built-up immunity more easily than other variants,” says IHME co-author Dr. Hasan Nassereldine. “The limited data we have on natural immunity protection from the Omicron variant and its sub-lineages underscores the importance of continued assessment, particularly since they are estimated to have infected 46% of the global population between November 2021 and June 2022. Further research is also needed to assess the natural immunity of emerging variants and to examine the protection provided by combinations of vaccination and natural infection.”
The researchers note some limitations of their study, cautioning that the number of studies examining the Omicron BA.1 variant and its sub-lineages and the number from Africa was generally limited. In addition, only limited data were available beyond 10 months after the initial infection. They also note that some information, such as past infection status and hospital admissions, was measured differently or incomplete, and could bias the estimate of protection.
Writing in a linked Comment, Professor Cheryl Cohen, National Institute for Communicable Diseases, South Africa, who was not involved in the study, says, “The high and sustained levels of protection conferred by previous infection against severe disease have important implications for COVID-19 vaccine policy. By September 2021, global SARS CoV-2 seroprevalence was estimated at 59%, with substantial variation in the proportion of immunity induced by infection or vaccination in different settings. Seroprevalence in Africa was estimated at 87% in December 2021, largely as a result of infection. High levels of immunity are an important contributor to the lower levels of severity observed with infection caused by emerging Omicron subvariants. As SARS-CoV-2 epidemiology shifts to more stable circulation patterns in the context of high levels of immunity, studies of the burden and cost of SARS-CoV-2 infection and risk groups for severe disease are needed to guide rational vaccination policy and decisions around prioritization in relation to other vaccine-preventable diseases.”
News
Breakthrough in Antimicrobial Technology with Cinnamon-Based Nanokiller
The need for innovative antimicrobial agents has become increasingly urgent due to the rise of antibiotic-resistant pathogens and the persistent threat of infections acquired during hospital stays. Traditional antibiotics and antiseptics are often ineffective [...]
The Silent Battle Within: How Your Organs Choose Between Mom and Dad’s Genes
Research reveals that selective expression of maternal or paternal X chromosomes varies by organ, driven by cellular competition. A new study published today (July 26) in Nature Genetics by the Lymphoid Development Group at the MRC [...]
Study identifies genes increasing risk of severe COVID-19
Whether or not a person becomes seriously ill with COVID-19 depends, among other things, on genetic factors. With this in mind, researchers from the University Hospital Bonn (UKB) and the University of Bonn, in [...]
Small regions of the brain can take micro-naps while the rest of the brain is awake and vice versa
Sleep and wake: They're totally distinct states of being that define the boundaries of our daily lives. For years, scientists have measured the difference between these instinctual brain processes by observing brain waves, with [...]
Redefining Consciousness: Small Regions of the Brain Can Take Micro-Naps While the Rest of the Brain Is Awake
The study broadly reveals how fast brain waves, previously overlooked, establish fundamental patterns of sleep and wakefulness. Scientists have developed a new method to analyze sleep and wake states by detecting ultra-fast neuronal activity [...]
AI Reveals Health Secrets Through Facial Temperature Mapping
Researchers have found that different facial temperatures correlate with chronic illnesses like diabetes and high blood pressure, and these can be detected using AI with thermal cameras. They highlight the potential of this technology [...]
Breakthrough in aging research: Blocking IL-11 extends lifespan and improves health in mice
In a recent study published in the journal Nature, a team of researchers used murine models and various pharmacological and genetic approaches to examine whether pro-inflammatory signaling involving interleukin (IL)-11, which activates signaling molecules such [...]
Promise for a universal influenza vaccine: Scientists validate theory using 1918 flu virus
New research led by Oregon Health & Science University reveals a promising approach to developing a universal influenza vaccine—a so-called "one and done" vaccine that confers lifetime immunity against an evolving virus. The study, [...]
New Projects Aim To Pioneer the Future of Neuroscience
One study will investigate the alterations in brain activity at the cellular level caused by psilocybin, the psychoactive substance found in “magic mushrooms.” How do neurons respond to the effects of magic mushrooms? What [...]
Decoding the Decline: Scientific Insights Into Long COVID’s Retreat
Research indicates a significant reduction in long COVID risk, largely due to vaccination and the virus’s evolution. The study analyzes data from over 441,000 veterans, showing lower rates of long COVID among vaccinated individuals compared [...]
Silicon Transformed: A Breakthrough in Laser Nanofabrication
A new method enables precise nanofabrication inside silicon using spatial light modulation and laser pulses, creating advanced nanostructures for potential use in electronics and photonics. Silicon, the cornerstone of modern electronics, photovoltaics, and photonics, [...]
Caught in the actinium: New research could help design better cancer treatments
The element actinium was first discovered at the turn of the 20th century, but even now, nearly 125 years later, researchers still don't have a good grasp on the metal's chemistry. That's because actinium [...]
Innovative Light-Controlled Drugs Could Revolutionize Neuropathic Pain Treatment
A team of researchers from the Institute for Bioengineering of Catalonia (IBEC) has developed light-activated derivatives of the anti-epileptic drug carbamazepine to treat neuropathic pain. Light can be harnessed to target drugs to specific [...]
Green Gold: Turning E-Waste Into a Treasure Trove of Rare Earth Metals
Scientists are developing a process inspired by nature that efficiently recovers europium from old fluorescent lamps. The approach could lead to the long-awaited recycling of rare earth metals. A small molecule that naturally serves [...]
Cambridge Study: AI Chatbots Have an “Empathy Gap,” and It Could Be Dangerous
A new study suggests a framework for “Child Safe AI” in response to recent incidents showing that many children perceive chatbots as quasi-human and reliable. A study has indicated that AI chatbots often exhibit [...]
Nanoparticle-based delivery system could offer treatment for diabetics with rare insulin allergy
Up to 3% of people with diabetes have an allergic reaction to insulin. A team at Forschungszentrum Jülich has now studied a method that could be used to deliver the active substance into the [...]