There has recently been some speculation that the human population, or at least some segments of it, may already have had sufficient COVID-19 infections to achieve the protective effect of herd immunity. There are also new studies using computational modeling that suggest that the population levels of immunity needed for broad protection are lowerthan the most common estimates of 60-66% immune. While these new and hypothetical constructs of infection-acquired herd immunity show useful directions for the future of public health research for both COVID-19 and other infectious diseases, there are still too many unknowns to use these numbers to design active health policy.
As I wrote earlier this year:
Many hard hit communities, such as the Hasidic community in the Borough Park neighborhood of Brooklynand other urban neighborhoods in London and Mumbai, have already had a substantial number of infections within distinct spatially contained groups, leading people to speculate that they may have established a protective level of immunity within these areas. In addition, many researchers have developed mathematical models of the outbreak and have come up with values lower than the typical estimates of the population needed for herd immunity for COVID-19, ranging from about 43% to as low as 10-20%.
The classical calculation of herd immunity is based on the infectivity of the virus in question, definedby the mathematical expression, 1-(1/R0). R0 (R-naught) is the basic reproductive number of the virus, which is an indicator of how easily an infection is transmitted. This is an estimate of the number of secondary cases generated by an infectious individual at the start of a novel outbreak, when the rest of the population is susceptible. There are many difficulties in estimating R0 during an active outbreak, resulting in some wide variations in estimates over time anddata coming from different geographic locations. Early WHO estimates turned out to be too low, but the most widely used estimates R0 for SARS-CoV-2 now remain at around 2.5 to 3, meaning that one infectious person will infect 2.5 to 3 others. The calculated estimate based on a R0 of 2.5 to 3 results in 60-66% percent of people needing to have immunity before there is any herd immunity effect for the population.
Herd immunity helps reduce the likelihood of disease transmission from infected individuals to non-immune individuals. Immunity can be acquired from vaccines or, in many cases, previous infection and recovery from the infection.
U.S. Government Accountability Office on Flickr.
A mathematical model recently published by Tom Britton and colleagues in Science suggests that because population groups vary by factors including age and rates of social activity and contact, herd immunity could established through illness and recovery with only around 43% of the population,instead of the 60% required using a classical model assuming an R0 of 2.5.
While this type of mathematical model for herd immunity is theoretically interesting since it attempts to capture contextual factors and elements of population heterogeneity, it is still too early to be directly applied to public policy. Our current knowledge about SARS-CoV-2 (the virus that causes COVID-19) is incomplete, including a lack of information about how we may develop immunity and how long immunity will typically last.Mathematical modeling isalso based on broad assumptions that are often untested in the real world. Much more research is needed before we know if these new ideas about herd immunity should be applied to public health interventions and planning.
There are generally two broad categories of infectious disease models: mechanistic models, which use scientific understanding of disease dynamics and human behavior, and statistical models, which rely only on patterns in the data
U.S. Government Accountability Office on Flickr.
The most striking example of how fast our understanding can change is the recent confirmation of a reinfection with a second case of COVID-19 after four and a half months in Hong Kong.Unlike earlier reports of reinfection, which were mainly anecdotal, this case was confirmed based on viral genome sequencing, showing that the second infection was from a genetically distinct strain. This suggests that reinfection is an important possibility and that immunity acquired through illness and recovery may last only months. This new case adds additional elements of uncertainty to Britton and colleagues model, since the authors state that their current model was designed based on the assumption that infection with and subsequent clearance of the virus leads to immunity against further infection for an extended period of time.
Reinfection and the typical duration of immunity are not the only uncertainties. It also remains unclear to what degree immunity is antibody-mediated versus cell-mediated, whichkinds of antibodies are most important, whether immunity might prevent future disease or only make reinfections less severe, and whether prior exposure to common cold coronaviruses offer any protection. Immune response also may depend on characteristics beyond age, including biological sex and individual genetic variation, and other factors. The data available is often incomplete, meaning that mathematical models may be based on biased samples; underreporting of data has been high, and areas without sufficient testingdo not provide adequate data.
There are also a number of difficulties inherent in using the basic reproductive rate to predict disease spread, and it is difficult to disentangle the basic rate R0 from the actual transmission rate (Rt), which is impacted by changes in behavior and in population immunity over time. If done properly, all of the measures meant to control the virus, including lockdowns, social distancing, business closures, travel bans, mask wearing, and contact tracing, will reduce the transmission. While this is a good thing for the publics health, it makes the data collected ambiguous: has disease transmission has been slowed by public health measures, or is it waning naturally?
Current estimates suggest that a person infected with COVID-19 will, on average, pass the virus to 2-3 other people.
United Nations COVID-19 Response on Unsplash.
There are also speculations that the amount of virus a person contacts impacts the severity of illness (this is known asa dose-response relationship), potentially explaining why masking is effective. It is still unclear to what degree seasonality plays a role in transmission, and more research is needed on the exact mechanisms of virus spread and persistence in the air and the role of indoor conditions such as humidity, temperature, and ventilation. Finally, once a vaccine becomes available, it will impact herd immunity, though the results will depend both on the effectiveness and the distribution of any future vaccines as well as whether people are willing to get the vaccine at all.
Throughout this pandemic, the concept of herd immunity has been frequent fodder for wishful thinking. Some countries, including Britain and Sweden, attempted to rely on herd immunity rather than implementing broad control measures. Now Britain has reconsidered this plan, and Sweden has sustained much larger spread of the disease and greater number of deaths than its neighbors.
In the United States, wishful thinking about the virus disappearing on its ownhas delayed needed intervention and prompted premature reopening. Pandemic control measures have many unpleasant side effects, and herd immunity can be an appealing concept for those who seek reassurance that the world will eventually return to normal, but our best way forward requires an understanding that conducting quality research and applying it effectively to policy take time and a great deal of work.
Go here to read the rest:
Don't bank on herd immunity to save us from COVID-19 - Massive Science
- How Smart Cities Are Redesigning Human Behavior - Lakeland Connect - June 10th, 2025 [June 10th, 2025]
- HUMAN TRAFFICKING | 'That was normal behavior': Victim recalls being 'sold' by her mother, then the aftermath of abuse - The Tribune-Democrat - June 10th, 2025 [June 10th, 2025]
- Tech company unveils eerie new way to map human behavior: 'We're tokenizing the invisible ones' - The Cool Down - June 1st, 2025 [June 1st, 2025]
- Simulating Human Behavior with AI Agents - Stanford HAI - May 21st, 2025 [May 21st, 2025]
- 'Human behavior is the basis of the energy transition' - ioplus.nl - May 21st, 2025 [May 21st, 2025]
- Driverless taxi ride surprises with human-like behavior - Alton Telegraph - May 21st, 2025 [May 21st, 2025]
- VeChains Bold Vision to Tokenize Human Behavior - 99Bitcoins - May 21st, 2025 [May 21st, 2025]
- Study links most alligator attacks to risky human behavior - Gulf Coast News and Weather - Southwest Florida News - April 27th, 2025 [April 27th, 2025]
- UF study finds risky human behavior is the cause for most alligator bites - The Palm Beach Post - April 19th, 2025 [April 19th, 2025]
- Study Finds 96% of Gator Bites Are the Result of Risky Human Behavior - Gizmodo - April 19th, 2025 [April 19th, 2025]
- A Growing Pathway to Understanding Human Behavior - University of Northern Colorado - April 19th, 2025 [April 19th, 2025]
- The Rehearsal S2: Nathan Fielder Explores Human Behavior - Hollywood.com - April 19th, 2025 [April 19th, 2025]
- A Bad Rap: Most alligator bites are caused by risky human behavior, UF researchers say - WCJB TV20 - April 19th, 2025 [April 19th, 2025]
- AI humanoid robot learns to mimic human emotions and behavior - Fox News - April 19th, 2025 [April 19th, 2025]
- INTERVIEW: Dying for Sex Director Shannon Murphy on Portraying Authentic Human Behavior by Blending Comedy & Drama - The Knockturnal - April 10th, 2025 [April 10th, 2025]
- 7 Must-Read Psychology Books That Will Help You Decode Human Behavior - Times Now - April 10th, 2025 [April 10th, 2025]
- Vet shares warning against common human behavior that gives dogs anxiety - The Mirror US - March 30th, 2025 [March 30th, 2025]
- BBVA Foundation awards the psychologists who changed the way we understand and predict human behavior - WebWire - March 15th, 2025 [March 15th, 2025]
- Human behavior is driven by fifteen key motives - Earth.com - February 25th, 2025 [February 25th, 2025]
- Nature Human Behavior is back, this time touting allyship - Why Evolution Is True - February 25th, 2025 [February 25th, 2025]
- 30 Times Courtrooms Became The Stage For The Strangest Human Behavior - Bored Panda - February 3rd, 2025 [February 3rd, 2025]
- The Impact of AI on Human Behavior: Insights and Implications - iTMunch - January 23rd, 2025 [January 23rd, 2025]
- Disturbing Wildlife Isnt Fun: IFS Parveen Kaswan Raises Concern Over Human Behavior in Viral Clip - Indian Masterminds - January 15th, 2025 [January 15th, 2025]
- The interplay of time and space in human behavior: a sociological perspective on the TSCH model - Nature.com - January 1st, 2025 [January 1st, 2025]
- Thinking Slowly: The Paradoxical Slowness of Human Behavior - Caltech - December 23rd, 2024 [December 23rd, 2024]
- From smog to crime: How air pollution is shaping human behavior and public safety - The Times of India - December 9th, 2024 [December 9th, 2024]
- The Smell Of Death Has A Strange Influence On Human Behavior - IFLScience - October 26th, 2024 [October 26th, 2024]
- "WEIRD" in psychology literature oversimplifies the global diversity of human behavior. - Psychology Today - October 2nd, 2024 [October 2nd, 2024]
- Scientists issue warning about increasingly alarming whale behavior due to human activity - Orcasonian - September 23rd, 2024 [September 23rd, 2024]
- Does AI adoption call for a change in human behavior? - Fast Company - July 26th, 2024 [July 26th, 2024]
- Dogs can smell human stress and it alters their own behavior, study reveals - New York Post - July 26th, 2024 [July 26th, 2024]
- Trajectories of brain and behaviour development in the womb, at birth and through infancy - Nature.com - June 18th, 2024 [June 18th, 2024]
- AI model predicts human behavior from our poor decision-making - Big Think - June 18th, 2024 [June 18th, 2024]
- ZkSync defends Sybil measures as Binance offers own ZK token airdrop - TradingView - June 18th, 2024 [June 18th, 2024]
- On TikTok, Goldendoodles Are People Trapped in Dog Bodies - The New York Times - June 18th, 2024 [June 18th, 2024]
- 10 things only introverts find irritating, according to psychology - Hack Spirit - June 18th, 2024 [June 18th, 2024]
- 32 animals that act weirdly human sometimes - Livescience.com - May 24th, 2024 [May 24th, 2024]
- NBC Is Using Animals To Push The LGBT Agenda. Here Are 5 Abhorrent Animal Behaviors Humans Shouldn't Emulate - The Daily Wire - May 24th, 2024 [May 24th, 2024]
- New study examines the dynamics of adaptive autonomy in human volition and behavior - PsyPost - May 24th, 2024 [May 24th, 2024]
- 30000 years of history reveals that hard times boost human societies' resilience - Livescience.com - May 12th, 2024 [May 12th, 2024]
- Kingdom of the Planet of the Apes Actors Had Trouble Reverting Back to Human - CBR - May 12th, 2024 [May 12th, 2024]
- The need to feel safe is a core driver of human behavior. - Psychology Today - April 15th, 2024 [April 15th, 2024]
- AI learned how to sway humans by watching a cooperative cooking game - Science News Magazine - March 29th, 2024 [March 29th, 2024]
- We can't combat climate change without changing minds. This psychology class explores how. - Northeastern University - March 11th, 2024 [March 11th, 2024]
- Bees Reveal a Human-Like Collective Intelligence We Never Knew Existed - ScienceAlert - March 11th, 2024 [March 11th, 2024]
- Franciscan AI expert warns of technology becoming a 'pseudo-religion' - Detroit Catholic - March 11th, 2024 [March 11th, 2024]
- Freshwater resources at risk thanks to human behavior - messenger-inquirer - March 11th, 2024 [March 11th, 2024]
- Astrocytes Play Critical Role in Regulating Behavior - Neuroscience News - March 11th, 2024 [March 11th, 2024]
- Freshwater resources at risk thanks to human behavior - Sunnyside Sun - March 11th, 2024 [March 11th, 2024]
- Freshwater resources at risk thanks to human behavior - Blue Mountain Eagle - March 11th, 2024 [March 11th, 2024]
- 7 Books on Human Behavior - Times Now - March 11th, 2024 [March 11th, 2024]
- Euphemisms increasingly used to soften behavior that would be questionable in direct language - Norfolk Daily News - February 29th, 2024 [February 29th, 2024]
- Linking environmental influences, genetic research to address concerns of genetic determinism of human behavior - Phys.org - February 29th, 2024 [February 29th, 2024]
- Emerson's Insight: Navigating the Three Fundamental Desires of Human Nature - The Good Men Project - February 29th, 2024 [February 29th, 2024]
- Dogs can recognize a bad person and there's science to prove it. - GOOD - February 29th, 2024 [February 29th, 2024]
- What Is Organizational Behavior? Everything You Need To Know - MarketWatch - February 4th, 2024 [February 4th, 2024]
- Overcoming 'Otherness' in Scientific Research Commentary in Nature Human Behavior USA - English - USA - PR Newswire - February 4th, 2024 [February 4th, 2024]
- "Reichman University's behavioral economics program: Navigating human be - The Jerusalem Post - January 19th, 2024 [January 19th, 2024]
- Of trees, symbols of humankind, on Tu BShevat - The Jewish Star - January 19th, 2024 [January 19th, 2024]
- Tapping Into The Power Of Positive Psychology With Acclaimed Expert Niyc Pidgeon - GirlTalkHQ - January 19th, 2024 [January 19th, 2024]
- Don't just make resolutions, 'be the architect of your future self,' says Stanford-trained human behavior expert - CNBC - December 31st, 2023 [December 31st, 2023]
- Never happy? Humans tend to imagine how life could be better : Short Wave - NPR - December 31st, 2023 [December 31st, 2023]
- People who feel unhappy but hide it well usually exhibit these 9 behaviors - Hack Spirit - December 31st, 2023 [December 31st, 2023]
- If you display these 9 behaviors, you're being passive aggressive without realizing it - Hack Spirit - December 31st, 2023 [December 31st, 2023]
- Men who are relationship-oriented by nature usually display these 9 behaviors - Hack Spirit - December 31st, 2023 [December 31st, 2023]
- A look at the curious 'winter break' behavior of ChatGPT-4 - ReadWrite - December 14th, 2023 [December 14th, 2023]
- Neuroscience and Behavior Major (B.S.) | College of Liberal Arts - UNH's College of Liberal Arts - December 14th, 2023 [December 14th, 2023]
- The positive health effects of prosocial behaviors | News | Harvard ... - HSPH News - October 27th, 2023 [October 27th, 2023]
- The valuable link between succession planning and skills - Human Resource Executive - October 27th, 2023 [October 27th, 2023]
- Okinawa's ants show reduced seasonal behavior in areas with more human development - Phys.org - October 27th, 2023 [October 27th, 2023]
- How humans use their sense of smell to find their way | Penn Today - Penn Today - October 27th, 2023 [October 27th, 2023]
- Wrestling With Evil in the World, or Is It Something Else? - Psychiatric Times - October 27th, 2023 [October 27th, 2023]
- Shimmying like electric fish is a universal movement across species - Earth.com - October 27th, 2023 [October 27th, 2023]
- Why do dogs get the zoomies? - Care.com - October 27th, 2023 [October 27th, 2023]
- How Stuart Robinson's misconduct went overlooked for years - Washington Square News - October 27th, 2023 [October 27th, 2023]
- Whatchamacolumn: Homeless camps back in the news - News-Register - October 27th, 2023 [October 27th, 2023]
- Stunted Growth in Infants Reshapes Brain Function and Cognitive ... - Neuroscience News - October 27th, 2023 [October 27th, 2023]
- Social medias role in modeling human behavior, societies - kuwaittimes - October 27th, 2023 [October 27th, 2023]
- The gift of reformation - Living Lutheran - October 27th, 2023 [October 27th, 2023]
- After pandemic, birds are surprisingly becoming less fearful of humans - Study Finds - October 27th, 2023 [October 27th, 2023]