Children develop stronger immunity after repeated infections in nursery

Young children who attend nursery get sick more often than those who don't, but they will go on to have fewer illnesses during early school years, finds a new review of evidence by a group of parent-scientists involving University College London (UCL) researchers.

All five authors of the new Clinical Microbiology Reviews paper are parents of young children, who are also researchers or clinicians at UCL, the University of Cambridge, Cornell University and North Middlesex University Hospital. They wanted to understand how often children typically get sick when attending nursery, why they're so prone to illness, what impact it has on their immune systems, and what parents can do to help.

The researchers stress that vaccination remains the best way to protect against childhood illness.

Co-author Dr Lucy van Dorp, an infectious disease genomics researcher in the UCL Genetics Institute, said: "As parents, we were all struck by how often our collective nine children became ill after starting nursery. So we came together to do the first review of how often a child starting nursery will get sick in their first year of attendance and what can be done about it."

The study brings together evidence across epidemiology, immunology and vaccination, and highlights that recurrent illness on starting nursery is normal. The authors suggest a typical one-year-old starting nursery will experience around 12–15 respiratory infections, two gastrointestinal illnesses (diarrhoea and vomiting), and one or two rash-causing infections in the first year alone – which will all have a substantial knock-on effect for working parents.

Our lived experience of parents seeing a high burden of infections after a child starts nursery is backed up by the evidence."

Dr Lucy van Dorp, infectious disease genomics researcher, UCL Genetics Institute

The study's corresponding author Dr Charlotte Houldcroft, a virologist at the University of Cambridge, said: "We all have experience of our children coming home from nursery with a bug that leaves them, and often us, feeling pretty poorly – even occasionally needing hospital care.

"But it's important for parents to follow guidelines to keep children home from nursery while unwell – and potentially for another day or two after recovery, depending on the type of infection. While infections during nursery are normal and common, it's important to do what we can to mitigate their spread."

And this does get better with time, as the norm of near-monthly respiratory infections improves with each passing year; older children are less likely to test positive for a virus at any one time and are less likely to have symptoms.

Dr van Dorp said: "Employers need to recognise that it's normal for parents of young children to regularly need to take time off work to care for their children, and will also be more prone to getting sick themselves – but this will improve as the child ages."

The researchers found evidence that young children are particularly prone to getting sick largely due to their immature immune systems – before they gradually develop more mature adaptive immune responses – and the inherent transmissibility of childhood pathogens, rather than because of poor hygiene or childcare practices in nurseries.

Co-author Dr Leo Swadling (UCL Institute of Infection, Immunity & Transplantation) said: "Newborns have some protection against infection thanks to antibodies passed from the mother, but this wanes in their first year, leaving infants – especially those starting childcare – more vulnerable to infections. It's normal for children to get sick a lot because their immune systems have never seen these bugs before – but then nursery serves as a 'boot camp' for their immune systems, building up resilience for the years ahead."

The researchers found evidence that children who attend nursery at a young age experience more infections from age one to five than those who remain at home until starting school – but then once they've started school, this pattern is reversed as children without prior childcare experience get sick more often. Early exposure in group childcare settings appears to confer some protection for the early school years, likely due to acquiring immunity to common infections.

The authors stress that vaccination is one of the most effective things parents can do to protect their children from nursery illnesses, such as the new MMRV vaccine that protects children against measles, mumps, rubella and chickenpox.

Dr Swadling said: "Vaccines are a key way to protect children from serious infections in childcare, so we encourage parents to keep their children up to date with all available vaccines."