Daycare infections

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This text is part of: "I would never send my kids to school" by Piotr Wozniak (2017)

Kids get sick often

Many families report awful struggles with infections brought in from daycare. Those struggles often take down whole households. The link between daycare and infections is well established. However, recent research that points to immune benefits of daycare has skewed the picture. Today, many parents believe that daycare is good for health. Such a claim is often only an excuse for those who feel guilty about abandoning kids to an institution. This is also a good excuse for me to present my own view on how healthy immune system develops, and how it can be well taken care of. One of the main reasons I decided to write a few words in the context of daycare is that I believe that my own system for developing strong innate immunity is worth recommending and shows how innate immunity can play a role well into adulthood. This also means that adaptive immunity, which helps us recover from colds and flu, isn't too effective in preventing colds and flu in the first place. This goes against a popular myth that sending kids to daycare can help avoid cold and flu viruses later in life.

Natural vaccination

Daycare works like "indoor vaccination" for kids. Kids do indeed show sturdier immunity to a wider spectrum of bugs. The costs are horrendous though. Chronic ear infections, or sinusitis take their toll for years to come and affect development and long-term health. In families with many kids, the infections take over the entire household, including the adults. At times of flu epidemics, the whole society seems to grind to a halt as if in economic depression. For kids in home care and for homeschoolers, this is hardly ever a problem. They get their own exposure but can manage infections in a rational manner, often without even experiencing any symptoms. All forms of exposure in a playground or in the woods are welcome. This is the place where the kid is stronger and the bugs are weaker. This is much closer to "natural vaccination" than the human-made incubators of microbial life such as daycare centers or pre-school. Research that compares kids with or without daycare experience should take into account that those taken care of at home are often sheltered and shielded to an irrational degree. Overprotectiveness definitely correlates with the wish to stay in control and keep the kid at home. Daycare exposure may have its benefits, but a limited, perfectly-timed exposure in a gym, outdoors, or in a swimming pool can play the same role, and safely.

We usually underestimate the power of a toddler's immune system and overestimate the importance of exposure in protecting the adults from infections such as common cold. There are hundreds of cold viruses, they keep mutating, and even influenza comes in a different shape each season. In that sense, our immune system does not improve that much from year to year in being able to combat colds or influenza. We might as well toss those infections away from our investigations of adaptive immunity and focus on their diagnostic value for innate immunity that differs widely across the population. However, epidemiologists regularly bag together infections that are of viral and bacterial origin. Those which are primary and those that come in the wake of other infections. Those that are transmitted, and those that come from within the host. Those tackled with adaptive immunity and those that can only be taken care of with innate immunity.

For example, for ear infections, we should remember that they are often caused by the same pathogen harbored safely in between infections. Again, incidents may correlate better with overall health or with innate immunity than they correlate with adaptive immunity built at first exposure.

Daycare immunity myth

Dr Sylvana M. Cote is a psychologist at the University of Montreal in Quebec. She is concerned with the development of children in disadvantaged families affected by poverty or mother's lower education level. She is no expert in immunology, however, she is a believer in the power of daycare, and she got a great deal of her own research to back up her claims. In a precious study of infections in kids, she compared daycare infections with home care infections, and infections at elementary school level. She found that kids got more infections in group care, but those would be compensated by fewer infections at school age. As this was a pioneering study, the press release made huge ripples around the world in all major news channels: Reuters, CNN, NBC, Forbes, New York Times, all daycare news sites, activist mom blogs, feminist mom blogs, etc. Commentary from independent researchers, child psychologists, and immunity experts was absent. All channels reproduced the same unadulterated press release with no commentary of their own experts. Female news anchors punched the air: "Yeah! Good news for working moms at last". Blogger moms picked the news up fast with enthusiasm: "3 Science-Backed Reasons Why Working Moms Can Let Go of the Guilt Now". Finally parents could feel better: "Daycare is good for immunity!" Soon the message was twisted further into a harmful daycare propaganda: "those who stay at home will have constantly runny noses".

This is one more case to show how a fantastic study can be used to do an awful job of myth-making. Good research is now encouraging child-parent separation and institutionalization. Dr Cote focused her career on employing day care in the betterment of society. In this case, her research will be used for years or decades to perpetuate an unhealthy myth. We all know that duplication studies are poorly funded. If they modify or contradict the initial result, and the result is not pleasing, they will make no news. A similar Dutch study from a year before went unnoticed. It was said to "debunk the hygiene hypothesis". Perhaps a different headline made the difference: "Early Daycare Is Associated with an Increase in Airway Symptoms in Early Childhood but Is No Protection against Asthma or Atopy at 8 Years". The correct interpretation of Cote's research may drown in the media noise. The myth was born and we will have to live with it.

Here is the original paper with the most essential results summarized in this table. The design seems spotless. The results interesting and significant. However, I am instantly struck with a major flaw in reasoning that is used to justify daycare on the basis of the said data. People who keep their kids at home are predominantly overprotective. Love is a good thing, but in this hazard-ridden world, it often leads to erroneous strategies. In my own neighborhood some families petitioned for cutting trees because they "increase the incidence of allergies, asthma and cancer" (no kidding!). Natural world is seen as the source of danger and disease. Cages of concrete and glass are considered safe. Daycare is also avoided because it is a "cesspool of germs". Along the lines of the "hygiene hypothesis", those strategies are indeed likely to lead to an increase in immune disorders. As the research was based on interviews with parents, it is also easy to notice that those overprotective types will also tend to be more scrupulous in reporting infection or even do some "over reporting", while parents of kids in daycare will best remember days of most severe infections when they had to stay at home with kids. "Minor infections" can easily be forgotten if someone else takes care of the kid.

Despite a solid sample (n=1238), the noise in data is still significant. If someone tried to use the results to claim that short breastfeeding span reduces infections, or low birth weight may benefit gastrointestinal immunity, he would be accused of p-hacking.

Conclusions of Cote's paper say "Physicians may reassure parents that infections during the first child care years do not lead to a higher overall burden of infections". Considering the results, the claim is correct, however, it refers to an average child, while it is definitely false in reference to a child whose immunity is taken seriously by proper care and exposure. To extend that reasoning to the main theme of this book, instead of saying "Parents can be reassured that kids get some learning at school", we should emphatically state that schools produce learning that uses only a tiny fraction of a child's true potential. Naturally, it is not the job of a scientific paper to go beyond the scope of its own findings. If so, that good hearted reassurance goes a step too far.

The mythmaking in the wake of the article begins innocently and unintentionally. The first step has already been committed in the same issue of the same journal (Archives Pediatr Adolesc Med) that added a commentary in the "advice for patients" category. Therein, Dr Megan Moreno says that children in group care, who suffer mild infections, have fewer infection during school years. This is true. However, there are five problems with this statement: (1) Probably all children in group care suffer from mild infections. (2) The statement was attributed to Dr Sylvana Cote's findings published in the same issue, which is not true. (3) Dr Cote did not differentiate between mild and severe infections. When she mentioned mild infections, it was about a (4) hypothetical mechanism, which was to later reduce (5) asthma (not infections).

The most serious implication of this tiny misrepresentation is that it subliminally implies: "kids in child care get mild infection which improve their immunity", while the truth is "kids in child care get serious infections that come earlier than similar infections in homecare". The mis-statement would not be a big deal if it was not committed in the context of "advice to patients" that later resulted in screaming media headlines.

There is a clear dependence of the recommendation on our priorities. Do we aim at maximizing immunity, well-being, and academic achievement of an average child, or do we look for the optimum long-term cognitive development strategy for a concerned parent.

In a short footnote, the research importantly remarks that the total overall burden of disease seems to be comparable for kids in home care and daycare. The author of the study, Dr Cote, commented for news media that school period is more critical and parents may wish to work on that early immunity: "there is an advantage of not missing school days, when they're missing major education that's really the basis of their academic trajectory". This is the opposite to what I would conclude! In optimizing development, it is the earliest years in the critical period where cognitive growth opportunities should be most protected.

Cognitive development counts more than academic achievement!

If so, Cote's research implies:

If daycare shifts the burden of disease to earlier ages, it contributes to worse long-term cognitive outcomes.

The headlines should rather say "Daycare shifts infections to earlier ages", while the article or the commentary should explain the importance of the measured exposure to pathogens. The change we need is not to send more kids to daycare, but to educate parents on best strategies for developing a healthy immune system (see below).

Impact of co-infections

Despite a popular myth, co-infections with chronic pathogens will often have a negative impact on overall immunity. Bystander infections can even impact the efficiency of vaccination. The positive or negative impact of co-infections seems to depend on the infection phase and pathogen competitive effects.

The safest strategy for building up adaptive immunity is to tackle infections one at a time.

Needless to say, symptomless infections are most desirable from a parent's point of view. We simply want kids to get strong without getting sick.

The problem with daycare is that infections come in waves, become chronic, there is no full recovery, same pathogens become resurgent over and over again. Compromised respiratory mucosa, sinuses, middle ear, gastrointestinal epithelia, reduced mucosal innate immunity, ravaged gut microbiota, and other elements of innate immunity provide open gateways to more pathogens, even those which would normally cause few problems and for which the adaptive immunity has already been established. This leaves the kids exposed to serious complications from otherwise innocent diseases.

Exposure is good, sickness is not! Secondary and opportunistic infections are a waste of resources, incl. health and opportunistic cognitive development costs.

Daycare culture

Research conducted in Canada may not necessarily quantitatively translate to other countries. A great deal depends on national culture and practises used in specific facilities: drugs used to suppress fever, antibiotics, care standards, etc. Literature is rich on abuse of antibiotics and how care providers and parents provide feedback loops of conditioning and abuse. Statistics show that daycare kids are twice as likely to use antibiotics. Parents may be tempted to cover up symptoms, e.g. fever, to ensure admission and minimize disruption to their own schedule. This naturally affects herd immunity and opens gateways to chronic infections in the entire group.

Old friends hypothesis

Along Dr Graham A. W. Rook's "old friend" hypothesis proposed in 2003, the best ways of developing acquired immunity and a healthy immune system come with a farmer's lifestyle or with exposure to farmland or other natural environments. Pathogenic constellations encountered in infant nurseries are a product of recent microbial evolution that accompanied the increase in daycare as of 1840. Those microbiota keep evolving to adapt to the whole array of antibiotics we keep using to combat disease. Gastrointestinal bacteria are particularly important for developing natural immunity. This is a prime ingredient missing in daycare where kids are constantly injected with new infections that necessitate involvement of antibiotics. Rook believes that it is not the exposure to childhood viral diseases, colds, or influenza that determine the susceptibility to autoimmune diseases, but the exposure to microbes that have been accompanying humans in the course of evolution (incl. the hunter-gatherer stage). This Darwinian medicine approach suggests that whatever causes the observed decrease in infection or auto-immune disease as a result of day care may be a result of an increased exposure to pathogens in general, not a specific effect of mild infections, such as colds.

Twisted exposure logic

A simple mental experiment explains why using daycare as "indoor vaccination" is an awful strategy.

Consider a better approach to immunity: let the kid get her sleep out, get her fed or breastfed, and only when she is ready to meet other kids go to outdoors daycare, stay with the kid if she asks for your company, and let her play until she gets bored, says "enough", or asks for breastfeeding.

You can then provide an extra boost with exposure in the lake, river, farmland, woods, gym, or even in a swimming pool.

In this free-running approach, you will get a comparable or better exchange of pathogens in conditions of far better immune defenses for the child.

The message should not be: day care is good for immunity, but that home care needs to take better care of the immune system. Mere regular playground exposure would do comparable work to daycare.

If daycare infections are good, why do we recommend hand washing, or leaving sick kids at home in the same breath?

If exposure is good, and heavy exposure is better, why don't we visit a nearby hospital and lick a couple of bathroom door handles? Instead, we consider kiss-feeding of hunter-gatherer cultures "repulsive" (in kiss-feeding, mother offers an infant pre-masticated food).

We would never want to employ daycare exposure for our own health. Why are we ready to do it to our kids? And consider it a good thing? Because it is convenient!

Instead we should remember that there is an optimum level of exposure and an optimum mode of exposure. Daycare provides neither.

My own childhood infections

Personal anecdote. Why use anecdotes?
I have no recall or knowledge of my own sickness in daycare, but I definitely loved being sick in primary school. With a bit of cheating, I could fake a fever, and spend the whole day learning! Reading cartoons or painting was the type of learning I liked. It was my escape from the drudgery of school. In my case, missing schooldays was good for development!

Immunity workout

The myth that daycare is good for children health is destructive. It is based on misinterpretation of research. It is all but an excuse for many parents. It is true that the immune system needs its workout. However, the way it is done in daycare is the opposite of how this should be done!

In short, exposure is good, fully-blown infections are bad, secondary and opportunistic infections are even worse, and the regular use of antibiotics is a true disaster for long-term developmental prospects. For kids to build good immunity, send them to a farm, to the woods, or let them play with kids and animals in the playground. In addition, work on health, nutrition, rehydration, sleep, thermogenesis, play, and more.

If your kids get hundreds of infections, it is fantastic news as long as there are few or no symptoms. Sickness in daycare often means weeks off from care and from work for kids, siblings and parents. This often ends up with antibiotics or long-term complications from severe infections. Some health effects last a lifetime. It is amazing how many moms protect their kids with warm hats in the middle of the summer in the wake of ear infections.

Immune cells in little babies deprived of breastfeeding are like an army of soldiers who go to battle without their guns. The kid is left defenseless in the environment where pathogen exposure exceeds the optimum by an order of magnitude. This is often compounded by sleep deprivation, stress, problems with thermoregulation, limited mobility, and more (see: Baby management).

Exposure to a small dose of a single weakened pathogen is great. For a healthy kid, it is usually a matter of days before developing immunity without even showing a symptom. In daycare, there is a concentrated assault of multiple pathogens. Many of which are already pretty resistant to antibiotics. Even sturdy adults would succumb. Once the mucosa is wasted, once the natural flora is ravaged with antibiotics, the kid can take on a series of infections that would otherwise pose no threat. His own commensal bugs can have a field day. David Mills jokes: "The typical daycare center provides the stimulation and educational opportunity of a day in prison -- and spreads far more infection and communicable disease than the county jail".

Otitis media epidemic can be attributed to the prevalence of daycare. 2% of the population may be affected with extensive developmental and social implications. Hearing loss and language development problems may result.

And that's just the tip of the iceberg. Full analysis goes well beyond the scope of this article.

Kids who get fewer infections at younger ages may get more infections later. This is the fact for those who do not get their immune workout, and stay at home in isolation from the "hazards of the world". However, because of the fact that the total burden of disease is hypothesized to be similar, some pediatricians claim that it is better for small kids to get sick, esp. that those infections may have a milder course, than for older kids to miss school days. This is exactly the opposite of what we should do. It is the young developing brain that needs to have its playtime maximized. School age kids can learn at home, even when sick, if they chose so. Nevertheless, the ideal case is to develop immunity while minimizing actual sickness. So the case is moot. Reduced burden of infectious disease has been hypothesized as a contributor to the Flynn effect.

See also:


  • benefits of daycare for immunity are questionable
  • exposure to pathogens is good, sickness is not
  • daycare infections often produce consequences that last a lifetime
  • daycare infections often affect entire households
  • daycare shifts the burden of disease to younger ages which may have negative impact on long-term cognitive development
  • kids in home care are often overprotected, which weakens their immune system
  • media headlines which claim that home care weakens the immune system are misleading and dangerous
  • we tend to underestimate the power of newborns and toddlers to combat infections on their own
  • we tend to underestimate the power of innate immunity in combating colds and influenza
  • in most cases, the best care for young kids is provided by their biological mom with support of members of her family
  • handling infections one at a time seems to be a safe strategy
  • Graham Rook's "old friend" hypothesis implies that we should expose kids to pathogens from natural environments
  • daycare provides excessive exposure to particularly dangerous pathogens in conditions of weakened immune system