How have COVID-19 pandemic lockdowns affected our immune systems?


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?

How have lockdowns affected the immune systems of adults, children, and infants? Maskot/Getty Images

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?

Children and the ‘hygiene hypothesis’

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 BMJTrusted Source in 1989.

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.

Some microbes are friends, others are not

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 old friends (OF) mechanismTrusted Source.

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.


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