It is said that the strain of pneumonia caused by SARS-CoV-2 (new coronavirus) is mild when contracted by children. Is it really so?

I would like to share some research results, recorded by Chinese researchers in Pediatrics, a prominent academic journal of the American Academy of Pediatrics, regarding the actual situation of pediatric patients of COVID-19 in China, which started in Wuhan. The title of the article is "Epidemiological Characteristics of 2143 Pediatric Patients With 2019 Coronavirus Disease in China". This article is a pre-publication version to be published on Pediatrics, but it is already available on their website prior to publication.

The lead author of the article is Dr. Yuanyuan Dong of Shanghai Jiao Tong University School of Medicine, reporting on 2,143 cases of pediatric patients who were younger than 18 years old as of February 8, 2020. Dr. Dong and her colleagues first established criteria to diagnose COVID-19 and abstracted information on infected cases and suspected cases from data registered at the Chinese Center for Disease Control and Prevention. Infected cases are those who have a history of exposure to SARS-CoV-2 in China, particularly in the high risk area in Hubei Province, and have two of the following three conditions; 1) respiratory symptoms such as fever or cough, or gastrointestinal symptoms such as diarrhea; 2) decreased white blood cell count, increased lymphocyte count, or increased level of CRP (C-reactive protein), index for infection, in blood; 3) appearance of pneumonia on chest X-ray imaging.

After establishing the criteria, Dr. Dong and her colleagues divided the 2,143 cases of pediatric patients of COVID-19, including suspected cases depending on the severity of symptoms, into 5 categories as follows:

1. Asymptomatic infection: PCR tested positive with no symptoms
2. Mild: Only exhibiting symptoms of fever, cough, runny nose and diarrhea
3. Moderate: Developed pneumonia, but no shortness of breath or hypoxemia
4. Severe: Exhibiting fever, cough, gastrointestinal symptoms and pneumonia, having cyanosis or oxygen saturation in blood is less than 92%
5. Critical: Respiratory failure, Acute Respiratory Distress Syndrome (ARDS)

Among the 2,143 cases reported by February 8th, 731 are confirmed cases of COVID-19 by PCR tests, etc, while 1,412 were suspected cases judged by clinical manifestations.

The median age of the COVID-19 patients was 7 years. There were slightly more boys (56%) than girls, but there was no statistically significant difference. As for symptoms, there were 94 asymptomatic cases (4.4%), 1,091 mild cases (50.9%), 831 moderate cases (38.8%), while there were a lower number of severe and critical cases which accounted for 5.9%.

The age proportion of severe and critical cases (5.9%) was 10.6% for the age group of <1, 7.3% for 1-5, 4.2% for 6-10, 4.1% for 11-15, and 3.0% for 16 and above, revealing more severe cases in the younger age group. There was just one fatality, a 14-year old boy, among the 2,143 cases.

As is seen here, there were more mild cases of COVID-19 among juveniles under 18 years of age. However, a younger age does not necessarily mean milder symptoms. It was revealed that there was a tendency toward more severe cases among infants while no fatalities were recorded.

The reasoning by the authors as to why most of the children's cases were less severe was that children are shielded from adults and individual hygiene is better than that of adults' by handwashing, for example. It is also known that children are often susceptible to the common cold syndrome caused by the regular corona virus, which belongs to the same group as SARS-CoV-2. Therefore, it is possible that children already have an immune antibody that can react to SARS-CoV-2.

There is also another reasoning that the immune reaction of children is relatively weak due to their immune system still undergoing development, leading to a milder degree of inflammation in the lungs.

More research will be conducted on the pathology of SARS-CoV-2 not only among adults but also among children. I believe this article is significantly meaningful as a forerunner of such research papers.

Currently COVID-19 is spreading widely all over Japan. I am sure those who are raising children have a lot to be concerned about. This article supplies evidence that while severe cases leading to death are not non-existent among children, they are quite rare. As is indicated in this article, children have a greater degree of immunity to SARS-CoV-2 than adults.