Following the news this week of what appears to have been the first confirmed case of a Covid-19 reinfection, other researchers have been coming forward with their own reports. One in Belgium, another in the Netherlands. And now, one in Nevada.
What caught experts attention about the case of the 25-year-old Reno man was not that he appears to have contracted SARS-CoV-2 (the name of the virus that causes Covid-19) a second time. Rather, its that his second bout was more serious than his first.
Immunologists had expected that if the immune response generated after an initial infection could not prevent a second case, then it should at least stave off more severe illness. Thats what occurred with the first known reinfection case, in a 33-year-old Hong Kong man.
advertisement
Still, despite what happened to the man in Nevada, researchers are stressing this is not a sky-is-falling situation or one that should result in firm conclusions. They always presumed people would become vulnerable to Covid-19 again some time after recovering from an initial case, based on how our immune systems respond to other respiratory viruses, including other coronaviruses. Its possible that these early cases of reinfection are outliers and have features that wont apply to the tens of millions of other people who have already shaken off Covid-19.
There are millions and millions of cases, said Michael Mina, an epidemiologist at Harvards T.H. Chan School of Public Health. The real question that should get the most focus, Mina said, is, What happens to most people?
advertisement
But with more reinfection reports likely to make it into the scientific literature soon, and from there into the mainstream press, here are some things to look for in assessing them.
Whats the deal with the Nevada case?
The Reno resident in question first tested positive for SARS-CoV-2 in April after coming down with a sore throat, cough, and headache, as well as nausea and diarrhea. He got better over time and later tested negative twice.
But then, some 48 days later, the man started experiencing headaches, cough, and other symptoms again. Eventually, he became so sick that he had to be hospitalized and was found to have pneumonia.
Researchers sequenced virus samples from both of his infections and found they were different, providing evidence that this was a new infection distinct from the first.
What happens when we get Covid-19 in the first case?
Researchers are finding that, generally, people who get Covid-19 develop a healthy immune response replete with both antibodies (molecules that can block pathogens from infecting cells) and T cells (which help wipe out the virus). This is what happens after other viral infections.
In addition to fending off the virus the first time, that immune response also creates memories of the virus, should it try to invade a second time. Its thought, then, that people who recover from Covid-19 will typically be protected from another case for some amount of time. With other coronaviruses, protection is thought to last for perhaps a little less than a year to about three years.
But researchers cant tell how long immunity will last with a new pathogen (like SARS-CoV-2) until people start getting reinfected. They also dont know exactly what mechanisms provide protection against Covid-19, nor do they know what levels of antibodies or T cells are required to signal that someone is protected through a blood test. (These are called the correlates of protection.)
Why do experts expect second cases to be milder?
With other viruses, protective immunity doesnt just vanish one day. Instead, it wanes over time. Researchers have then hypothesized that with SARS-CoV-2, perhaps our immune systems might not always be able to prevent it from getting a toehold in our cells to halt infection entirely but that it could still put up enough of a fight to guard us from getting really sick. Again, this is what happens with other respiratory pathogens.
And its why some researchers actually looked at the Hong Kong case with relief. The man had mild to moderate Covid-19 symptoms during the first case, but was asymptomatic the second time. It was a demonstration, experts said, of what you would want your immune system to do. (The case was only detected because the mans sample was taken at the airport when he arrived back in Hong Kong after traveling in Europe.)
The fact that somebody may get reinfected is not surprising, Malik Peiris, a virologist at the University of Hong Kong, told STAT earlier this week about the first reinfection. But the reinfection didnt cause disease, so thats the first point.
The Nevada case, then, provides a counterexample to that.
What kind of immune response did the person who was reinfected generate initially?
Earlier, we described the robust immune response that most people who have Covid-19 seem to mount. But that was a generalization. Infections and the immune responses they induce in different people are heterogeneous, said Sarah Cobey, an epidemiologist and evolutionary biologist at the University of Chicago.
Older people often generate weaker immune responses than younger people. Some studies have also indicated that milder cases of Covid-19 induce tamer immune responses that might not provide as lasting or as thorough of a defense as stronger immune responses. The man in Hong Kong, for example, did not generate antibodies to the virus after his first infection, at least to the level that could be detected by blood tests. Perhaps that explains why he contracted the virus again just about 4 1/2 months after recovering from his initial infection.
In the Nevada case, researchers did not test what kind of immune response the man generated after the first case.
Infection is not some binary event, Cobey said. And with reinfection, theres going to be some viral replication, but the question is how much is the immune system getting engaged?
What might be broadly meaningful is when people who mounted robust immune responses start getting reinfected, and how severe their second cases are.
Are people who have Covid-19 a second time infectious?
As discussed, immune memory can prevent reinfection. If it cant, it might stave off serious illness. But theres a third aspect of this, too.
The most important question for reinfection, with the most serious implications for controlling the pandemic, is whether reinfected people can transmit the virus to others, Columbia University virologist Angela Rasmussen wrote in Slate this week.
Unfortunately, neither the Hong Kong nor the Reno studies looked at this question. But if most people who get reinfected dont spread the virus, thats obviously good news.
What happens when people broadly become susceptible again?
Whether its six months after the first infection or nine months or a year or longer, at some point, protection for most people who recover from Covid-19 is expected to wane. And without the arrival of a vaccine and broad uptake of it, that could change the dynamics of local outbreaks.
In some communities, its thought that more than 20% of residents have experienced an initial Covid-19 case, and are thus theoretically protected from another case for some time. That is still below the point of herd immunity when enough people are immune that transmission doesnt occur but still, the fewer vulnerable people there are, the less likely spread is to occur.
On the flip side though, if more people become susceptible to the virus again, that could increase the risk of transmission. Modelers are starting to factor that possibility into their forecasts.
A crucial question for which there is not an answer yet is whether what happened to the man in Reno, where the second case was more severe than the first, remains a rare occurrence, as researchers expect and hope. As the Nevada researchers wrote, the generalizability of this finding is unknown.
Read more:
Several have been reinfected with Covid-19. Here's what that means - STAT
- Technion team discovers important adaptive strategy of the microbiome, impacting immune system - The Jerusalem Post - April 16th, 2024
- Targeting aging and age-related diseases with vaccines - Nature.com - April 16th, 2024
- Single cell analysis unveils B cell-dominated immune subtypes in HNSCC for enhanced prognostic and therapeutic ... - Nature.com - April 16th, 2024
- After the Smoke Clears: Scars on the Immune System - The Scientist - April 16th, 2024
- Exercise and the Immune System: What's the Latest Research? - Technology Networks - April 16th, 2024
- Analysis of immune cell infiltration characteristics in severe acute pancreatitis through integrated bioinformatics ... - Nature.com - April 16th, 2024
- Vaccination impairs de novo immune response to omicron breakthrough infection, a precondition for the original ... - Nature.com - April 16th, 2024
- Harnessing the power of the body's own cells to defeat cancer - Press Publications Inc. - April 16th, 2024
- Best Life: Immunotherapy targets brain cancer - Action News 5 - April 16th, 2024
- Dietary factors and their influence on immunotherapy strategies in oncology: a comprehensive review | Cell Death ... - Nature.com - April 16th, 2024
- New insights on B cells: Researchers explore building better antibodies and curbing autoimmune diseases - Medical Xpress - April 16th, 2024
- Immune cells' intense reaction to the coronavirus may lead to pneumonia - Science News Magazine - April 16th, 2024
- The telltale traces long Covid leaves in the blood - healthcare-in-europe.com - April 16th, 2024
- Overview of the Immune System - The Merck Manuals - March 18th, 2024
- SUNDAY Unraveling The Gut-Brain Connection: How Infant Gut Bacteria Shape Immune Resilience | TheHealthSit - TheHealthSite - March 18th, 2024
- Making drugs from T cells: The quantitative pharmacology of engineered T cell therapeutics | npj Systems Biology and ... - Nature.com - March 18th, 2024
- Study unlocks the mystery of neonatal neutropenia in newborns - News-Medical.Net - March 18th, 2024
- Vertebral Subluxation and Systems Biology: An Integrative Review Exploring the Salutogenic Influence of Chiropractic ... - Cureus - March 18th, 2024
- A new strategy to attack aggressive brain cancer shrank tumors in two early tests - ABC News - March 18th, 2024
- Turning on the Bat Signal - The Scientist - March 18th, 2024
- Power Foods That Can Support Your Immune System - Videos from The Weather Channel - The Weather Channel - March 18th, 2024
- Report: Aggressive brain tumors respond to new, immune-focused therapy - UPI News - March 18th, 2024
- Designer immune-cell therapy could shrink deadly brain tumors, early trials show - Livescience.com - March 18th, 2024
- 20.2: Introduction to the Immune System - Biology LibreTexts - February 27th, 2024
- Can one shot of yoghurt really boost your immunity and gut health? - Daily Mail - February 27th, 2024
- New cancer therapy approved by FDA supercharges bodys immune system - The Washington Post - February 27th, 2024
- How bubonic plague rewired the human immune system - BBC.com - February 27th, 2024
- Innovative therapy targets and destroys leukemia stem cells - News-Medical.Net - February 27th, 2024
- Participate in Our Study for $100; Open Slots This Week - University of Arkansas Newswire - February 27th, 2024
- Sexual dimorphism during integrative endocrine and immune responses to ionizing radiation in mice | Scientific Reports - Nature.com - February 27th, 2024
- Comprehensive pan-cancer analysis identifies the RNA-binding protein LRPPRC as a novel prognostic and immune ... - ScienceDirect.com - February 27th, 2024
- YOUR HEALTH: The HAMR fights cancer - WAFB - February 27th, 2024
- Cycles of a diet that mimics fasting can reduce signs of immune system aging, as well as insulin resistance and liver fat - News-Medical.Net - February 27th, 2024
- How the powerhouse of the cell could be cancers Achilles heel - Freethink - February 27th, 2024
- Food is medicine: The science behind zinc and other supplements for immune health - Healio - February 27th, 2024
- Unleashing Our Immune Response to Quash Cancer - Medscape - February 27th, 2024
- Tumor histoculture captures the dynamic interactions between tumor and immune components in response to anti-PD1 ... - Nature.com - February 27th, 2024
- Converging and evolving immuno-genomic routes toward immune escape in breast cancer - Nature.com - February 27th, 2024
- Sanjula Jain Urges a Comprehensive Approach in Address Alarming Rise in Cancer Cases Among Younger Populations - Managed Healthcare Executive - February 27th, 2024
- Cystic fibrosis breakthrough points to zinc as infection buster - New Atlas - February 27th, 2024
- Exploring synergies between B- and T-cell vaccine approaches to optimize immune responses against HIVworkshop ... - Nature.com - February 27th, 2024
- Is the 100-year old TB vaccine a new weapon against Alzheimers? - The Guardian - February 27th, 2024
- Immune system in the blood of Alzheimer's patients found to be epigenetically altered - News-Medical.Net - February 10th, 2024
- What impact does exercise have on your immune system? And how to stay well while cycling - BikeRadar - February 10th, 2024
- Had COVID recently? Here's what to know about how long immunity lasts, long COVID, and more - AAMC - February 10th, 2024
- Noor Momin harnesses the immune system to treat heart disease | Penn Today - Penn Today - February 10th, 2024
- Research reveals a process tumors use to induce immune suppressor cells and evade immunotherapy - Medical Xpress - February 10th, 2024
- Immune targeting of HIV-1 reservoir cells: a path to elimination strategies and cure - Nature.com - February 10th, 2024
- Preventing severe allergic reactions with nanoparticles - National Institutes of Health (NIH) (.gov) - February 10th, 2024
- Sugary handshakes are how cells talk to each other understanding these name tags can clarify how the immune ... - The Conversation Indonesia - February 10th, 2024
- Scientists have identified an immune cell that can cause allergies - EL PAS USA - February 10th, 2024
- Sickle cell and the importance of the immune system - Punch Newspapers - February 10th, 2024
- Which cancers can be treated with immune checkpoint inhibitors? - MD Anderson Cancer Center - February 10th, 2024
- How does waste leave the brain? Washington University School of Medicine in St. Louis - Washington University School of Medicine in St. Louis - February 10th, 2024
- Healthy Kids: Give your immune system a boost to stay healthy this winter - nbc16.com - February 10th, 2024
- The impact of prior exposure to hypoglycaemia on the inflammatory response to a subsequent hypoglycaemic episode ... - Cardiovascular Diabetology - February 10th, 2024
- Impact of Chronic Stress on Immune System and Depression | Health News - Medriva - February 10th, 2024
- I tried 'swamp soup,' the viral recipe that promises to boost your immune system - Yahoo News - February 10th, 2024
- Understanding Immune Checkpoint Inhibition Therapy: Challenges and Strategies - Medriva - February 10th, 2024
- One Simple Change May Dramatically Boost The Effect of COVID-19 Vaccines - ScienceAlert - February 10th, 2024
- The gut virome is associated with stress-induced changes in behaviour and immune responses in mice - Nature.com - February 10th, 2024
- Cancer vaccines are in the works to fight BRCA-linked gene mutations - The Philadelphia Inquirer - February 10th, 2024
- What are the organs of the immune system? - InformedHealth.org - NCBI ... - January 17th, 2024
- Novel insights into the immune response to bacterial T cell superantigens - Nature.com - January 17th, 2024
- FDA signs off on Takeda's HyQvia as maintenance therapy for CIDP - FiercePharma - January 17th, 2024
- CBDs Pobezinsky and Pobezinskaya Use Flow Cytometry to Determine How Tumor Cells Outwit the Bodys Immune ... - UMass News and Media Relations - January 17th, 2024
- Boosting. What To Do. - Science Based Medicine - January 17th, 2024
- Axelia Oncology takes its TLR2/6 agonist into the clinic to harness the innate immune system - BioWorld Online - January 17th, 2024
- Long COVID manifests with T cell dysregulation, inflammation and an uncoordinated adaptive immune response to ... - Nature.com - January 17th, 2024
- Opinion | Thanks to mRNA, Future Drugs Will Be Easier and Faster to Make - Mississippi Free Press - January 17th, 2024
- Elon research team models the COVID immune response, one equation at a time - Today at Elon - January 17th, 2024
- Are plant-based meals good for your immune system? 4 things to know about improving your health this week. - Yahoo Life - January 17th, 2024
- Scientists Find Key To Potential Breast Cancer Prevention, Treatment | Newsroom - UNC Health and UNC School of Medicine - January 17th, 2024
- What if every germ hit you at the exact same time? An immunologist explains - The Conversation - January 17th, 2024
- Why Don't We Have a Staph Vaccine? - Healthnews.com - January 17th, 2024
- Best ways to improve your immune system - The Business Standard - January 17th, 2024
- Stanford University researchers think future pandemics could be prevented with universal vaccines - KGO-TV - January 17th, 2024
- Why you may feel depressed and anxious when you're ill and how to cope with it - The Conversation - January 17th, 2024
- New mechanism with potential to boost checkpoint-blocking cancer immunotherapies identified - Medical Xpress - January 17th, 2024
- Battling Bugs and Blues: The Interplay of Infection and Emotion - News-Medical.Net - January 17th, 2024