Question & Answer

The Evidence

• Due to public health restrictions, like lock-down, during the COVID-19 pandemic, people were less exposed to viruses that usually circulate.
• Some people were concerned that this could cause a decrease in immunity among the population, and that lifting the restrictions might lead to an increase in certain illnesses.
• Because so many types of illnesses are associated with viruses, we decided to concentrate only on childhood respiratory (breathing) diseases.
• We found one review that included four studies about a respiratory infection called respiratory syncytial virus or RSV. The review found that hospital admissions for RSV reduced during the COVID-19 pandemic in children under the age of 5. One of the studies in this review found no change in hospitalisation for conditions that were not related to viral infections or social distancing.
• We found 10 other individual studies that followed groups of people over time to see what the effect of restrictions might be respiratory illnesses.
• Ten reported from individual countries including France, New Zealand, Norway, Germany, England and Australia:
  • Three of these studies (Study 1, Study 2 and Study 3) found that rates of respiratory infections in children reduced during COVID-19 pandemic restrictions.
  • Seven studies compared rates of respiratory illnesses in children before, during and after public health restrictions (Study 4, Study 5, Study 6, Study 7, Study 8, Study 9 and Study 10). All found that rates fell in almost all the diseases studied during restrictions, and that they generally rose after restrictions were lifted.
  • One study found that during the lockdown, there were fewer cases of respiratory illnesses in young children. However, after the lockdown ended, some viruses continued to stay at low levels, while others did not.
• One study looked at rates of RSV (a common respiratory virus) in 18 different countries. The study found that during the pandemic, the rates of RSV decreased across all the countries studied. However, after the restrictions were lifted, rates of RSV increased in most of the countries (11 out of 18).
• Another study examined hospital admission rates for RSV (a common respiratory virus) in seven different countries for children aged 4 to 12 years. The study found that in these countries, the normal peak times for RSV-related hospital admissions were delayed by four to twelve months compared to previous seasons. Following these delays, two countries experienced an increase in RSV-related hospital admissions, two countries saw a decrease, and three countries did not report any changes.

Guidelines and recommendations

• We did not find any guidelines or recommendations on this topic.