Have COVID-19 lockdowns affected our immune systems?
The world is more than a year into the COVID-19 pandemic, so many people have been living with lockdown restrictions, quarantine periods, and physical distancing for an extended period of time. Hand sanitizer and masks are rife, and the common cold has not felt so common. But what will these lifestyle changes do to our health?
In this article, we look at what effect living physically distanced from other people might have on the immune systems of adults, children, and infants born during the pandemic.
Some people have voiced concerns over whether their immune systems are being challenged, given that the general public is no longer physically mixing.
Might our immune systems consequently “forget” how to fight off disease-causing agents? For adults and older children, there is some good news: This is not how immunity works.
According to MIT Medical, by the time a person reaches adulthood, their immune system has already had exposure to plenty of bacteria and viruses and is able to mount an attack against these invaders.
Because of this, the immune system has already learned how to destroy these microbes and will not forget, even in the wake of long-term lockdowns.
But what about younger children, whose immune systems are still in the learning phase?
Many parents and caregivers will be familiar with the so-called hygiene hypothesis, even if they do not know it by name.
It is essentially the idea that there is a link between the rise in allergic conditions and reduced exposure to microbes during childhood resulting from hygiene measures, such as frequent hand washing, introduced to protect children from infection.
Dr. David Strachan first proposed this link in an article that appeared in the
In a paper that appeared in the journal Perspectives in Public Health in 2016, Prof. Sally F. Bloomfield and colleagues examine Dr. Strachan’s original paper.
They write: “The immune system is a learning device, and at birth it resembles a computer with hardware and software but few data. Additional data must be supplied during the first year of life, through contact with microorganisms from other humans and the natural environment.”
They continue:
“If these inputs are inadequate or inappropriate, the regulatory mechanisms of the immune system can fail. As a result, the system attacks not only harmful organisms [that] cause infections but also innocuous targets such as pollen, house dust, and food allergens resulting in allergic diseases.”
Prof. Jonathan Hourihane, from the RCSI University of Medicine and Health Sciences in Dublin, Ireland, adds that the increases in eczema, asthma, hay fever, and food allergies over the past 30 years have likely resulted from decreased exposure to infections.
“We want to see children playing on the floor, getting dirty, and being exposed to lots of people in lots of environments,” he says. “The outcome of this is usually a strong immune system, linked to a healthy population of gut bacteria, called the microbiome.”
With this in mind, should parents of infants or young children be concerned about the effects of physical distancing and lockdowns on their immune systems?
Yes and no.
Prof. Bloomfield and colleagues write that while “evidence supports the concept of immune regulation driven by microbe-host interactions, the term ‘hygiene hypothesis’ is a misleading misnomer. There is no good evidence that hygiene, as the public understands, is responsible for the clinically relevant changes to microbial exposures.”
Their paper lays out how the idea that we have become “too clean” has remained in the public mind. Writing in 2016, Prof. Bloomfield and team prophetically note that this is also “happening at a time when infectious disease issues mean that hygiene is becoming more, rather than less, important.”
This is particularly relevant for respiratory viruses such as SARS-CoV-2, which causes COVID-19. Because viruses are not treatable with antibiotics, preventing them with hygiene practices such as washing the hands and cleaning surfaces is paramount.
The authors point to the post-hygiene hypothesis theory known as the
Introduced in 2003, it suggests that the important exposures to microbes in early life are not actually colds, measles, or other childhood ailments, but rather those microbes that were already around during the hunter-gatherer period, when the immune system was evolving.
These microbes include species that live in both indoor and outdoor environments, and they come from the skin, gut, and respiratory tracts of other people.
“OF exposures are vital,” say the researchers, “because they interact with the regulatory systems that keep the immune system in balance and prevent overreaction, which is an underlying cause of allergies. Diversity of microbial exposure is key.”
They note that the most important times in life for OF exposure are during pregnancy, delivery, and the first months of infancy. They also add that continuing exposure from the mother and siblings is vital.
Likewise, having pets increases the overall diversity of microbes in the home.
What about all the hand washing and sanitizing? Will these behaviors affect the immune responses of young people?
Prof. Bloomfield and colleagues suggest that they will not.
“The idea that we could create ‘sterile’ homes through excessive cleanliness is implausible; as fast as microbes are removed, they are replaced, via dust and air from the outdoor environment, […] commensal microbes shed from the human body and our pets, and contaminated foods brought into the homes.”
They note that changes in lifestyle and environment, including dietary changes and increased antibiotic use, as well as accelerated urbanization have all led to changes in our microbe exposure. This has likely contributed to the increase in allergic conditions such as eczema, hay fever, and food allergies.
However, the authors also note that “the public idea that obsessive hygiene and cleanliness is the root cause of the rise in allergies is no longer supported.”
Prof. Bloomfield and colleagues conclude their study by noting — and this is the positive news for parents of young children in the times of COVID-19 — “data are now strong enough to encourage […] natural childbirth, physical interaction between siblings and non-siblings, more sport, and other outdoor activities (including babies in prams).”
The takeaway here is that the lockdown walks that have become so popular for families stuck at home are beneficial for introducing infants to those crucial microbes.
If a person is able to breastfeed their child or get access to donated breast milk to feed them, this would also be beneficial — particularly in the absence of usual contact with more people and, therefore, more diverse microbes.
Researchers who published a study in the journal
This is because it “contains not only the basic nutrients (proteins, carbohydrates, and fats) but also a multitude of factors that drive development and maturation of the immune system and protect newborns from the environmental pathogens.”
They add that breast milk also contains immune cells such as lymphocytes, neutrophils, and macrophages, further boosting immunity.
However, Unicef UK cautions that breastfeeding rates could drop considerably during the pandemic due to a lack of support.
It says: “Many new mothers rely on friends and family to provide support and advice, and professional or voluntary sector services will also be unavailable during this time. As a result, rates of breastfeeding may drop substantially, leading to potential health issues for baby and mom.”
Having explored the physical aspects of immunity, we now turn our focus to the psychological effects.
Although adults and older children can breathe a sigh of relief knowing that their immune systems will remember how to fight off microbes, there is another piece of this puzzle to consider: stress.
Researchers Fulvio D’Acquisto and Alice Hamilton, who published a review in the journal
They point to previous animal studies that researchers conducted in socially isolated mice, primates, and other species.
They write: “Of note, high levels of inflammation are a driver for [cardiovascular disease]. Social isolation was linked to downregulation of type I and II interferons and an impaired response to infection by simian immunodeficiency virus.”
They note that in the wake of social isolation, it is the emotional rather than the physical separation that is the triggering factor in the body’s reduced ability to respond to adversity.
The authors add:
“As the period of time in lockdown and social distancing increases, distress and loneliness will increase; thus, it is likely that the aforementioned changes in the immune system would become more pronounced over time.”
Researchers have also observed such effects in humans.
According to a paper by Stanford researcher Firdaus S. Dhabhar, Ph.D., in the journal Immunologic Research, “chronic stress can suppress protective immune responses and/or exacerbate pathological immune responses.”
For adults, it is the stress of isolation and the pandemic, rather than the lack of interaction with microbes, that is a concern for the immune system.
Older children have faced unique challenges since March 2020, and several research teams are focusing on how these challenges may affect immunity for this age group.
A survey that researchers conducted in Canada and published in the International Journal of Behavioral Nutrition and Physical Activity analyzed the changes in movement and play behaviors in children immediately following the COVID-19 outbreak.
The results showed that only 4.8% of children and 0.6% of youths were meeting the combined movement behavior guidelines during this time.
Both children and youths had lower physical activity levels, spent less outside time, had higher leisure screen time, and got more sleep overall during the survey period.
The researchers note that healthy movement behaviors positively contribute to both the physical and mental health of young people, including the development of stronger immune systems. Therefore, these initial findings present some cause for concern.
The authors do note that family dog ownership and parental encouragement and support were positively linked to healthy movement behaviors.
Meanwhile, another survey — this time by the Children’s Commissioner’s Office in the United Kingdom — set out to understand how school-age children were experiencing stress during the initial lockdown period.
Researchers conducted surveys of around 2,000 school children aged 8–17 years in England in March and June 2020 to gauge the causes and frequency of their stress during lockdown.
Interestingly, they found that as lockdown progressed, many children felt stressed less often. Specifically, between March and June 2020, the percentage of children who felt stressed some of the time decreased from 47% to 34%, and the percentage of children who felt “rarely or never stressed” increased from 23% to 42%.
Based on survey response answers, the researchers speculate that the reason for the children’s stress levels decreasing during this period is that little, everyday worries went away during lockdown. Answers to the question, “What makes you feel stressed?” changed from the first survey to the second.
In the first survey, answers typically involved school, crowds, worries about their appearance, bullying, and allergies. In the second survey, such worries were absent, and their answers primarily focused on COVID-19.
It is not all good news on the stress front, however, as the survey also revealed that the greatest reported increase in stress during the lockdown period came from worries about school.
Just over 40% of children said that they felt more stressed about their schoolwork and exams while schools were closed.
For adults, children, and infants alike, getting outside and taking walks or engaging in other types of physical activity is beneficial for the immune system.
For adults and older children, getting fresh air and physical activity will likely help mitigate the effects of stress on immunity. For infants, having exposure to OF microbes outside will help contribute to the development of a robust immune system.
There are studies currently underway that are looking at what effect the pandemic is having on infants born during this period.
Clinical scientists at the RCSI University of Medicine and Health Sciences and CHI at Temple Street in Dublin, Ireland, are conducting research to see if the lockdown restrictions will result in an increase in allergies among infants born since March 2020.
The researchers will look at whether the decreased viral infection rate and improved air quality that resulted from the lockdown will make allergic conditions more or less common among infants whose families have experienced isolation and physical distancing.
As with many aspects of this pandemic, however, any definitive conclusions on this front are still to come. In the meantime, it is probably best to keep that hand sanitizer within arm’s reach.
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