8% of children with covid have transmitted it to their family

A Vall d'Hebron and primary healthcare study confirms that half of the children are asymptomatic

It is possible, but very rare, that a child's coronavirus infection becomes the trigger for a family outbreak. In most cases, it is adults who spread the virus to children and pre-adolescents. This is confirmed by a study carried out by the Vall d'Hebron Hospital and a hundred primary healthcare paediatricians, which concludes that only 8% of the 1,081 children diagnosed with covid between 1 July and 31 October in Catalunya transmitted the virus within their family nucleus. In total, 86 children can be considered the index case of a family outbreak in Catalunya. In the case of adults, the figure reaches 72.4%.

Researchers say that the study confirms that children do not usually transmit coronavirus. In 783 pediatric cases analyzed -from 0 to 18 years old-, in addition to the 3,515 family contacts of these positives, it was identified that an adult family member in direct contact with them had been infected -or had clinical symptoms- before the child. "The prospective study reaffirms that children are less likely to transmit the coronavirus than adults, as the first part of the study pointed out, whilst we were in lockdown", says Pere Soler, head of the Infectious Pathology and Immunodeficiency Unit of the Vall d'Hebron Paediatrics.

The prospective part of the study has included 1,081 patients from 0 to 18 years old with laboratory confirmed covid diagnosis who were taken care of by their primary healthcare pediatricians, "who have been responsible for collecting all the data on the cases and their intradomiciliary contacts", reports Dr. Anna Gatell, from the Alt Penedès-Garraf territorial pediatric team and representative of the primary healthcare pediatricians group. The epidemiological study has been carried out by both primary healthcare pediatricians and different hospitals, through a survey that families with pediatric cases of coronavirus have completed.

In the first part of this study, which was presented in August and analyzed the diagnoses between March 1st and May 31st, the conclusions pointed out that 3.4% of the pediatric patients were transmitters within their family nucleus. At that time, Soler had already stated that  children suffering from the disease were less likely to transmit the virus than adults in their family environment, despite the fact that this is a very close environment where it is difficult to maintain safety measures: " Now we can see why children moving freely, and their return to school, has not meant greater transmission numbers", declares Soler. "The amount of children affected in Catalunya continues to be scarce after the lockdown period, despite the fact that children now enjoy full mobility", evaluates the head of the service of preventive medicine and epidemiology of the Vall d'Hebron, Magda Campins.

The second part of the study was completed during the summer months, and it included the first seven weeks after the start of the school year. That is, before the second wave. The vast majority of the paediatric patients analysed have been secondary cases, says Soler, since home is a space with a considerable disease burden. "Six out of every ten cohabitants of the families participating in the study have been diagnosed with covid with microbiological confirmation", explains Soler. The family nucleus is one of the main spaces where the disease is transmitted, with 62.2% of positive PCR tests (2,161) of the 3,515 carried out in this area.

Asymptomatic and few hospitalizations

The study also confirms that 47% of the covid-infected children studied (506) are asymptomatic. Among those with symptoms, 70% suffered from fever and 37% from a cough. Headache (24%), fatigue (24%) and diarrhoea (16%) were the other most frequent symptoms. "Almost half of the infected children are asymptomatic, and it has been observed that the number of children requiring hospital admission for covid is still very low", says Dr. Antoni Soriano, from the Infectious Pathology and Immunodeficiency Unit of Pediatrics and researcher of the Infection in the Immunosuppressed Pediatric Patient research group of VHIR.

Only 2.5% of the pediatric patients (27 of a sample of 1,072) required hospitalization from July 1st to October 31st, while in the retrospective study (from March 1st to May 31st) this went up to 19%, with an average age of  12 years old. At the presentation of the first part of the study in August, the researchers stated that most admissions were made on a precautionary principle, in the face of any suspected respiratory disease.

Infants and very young children are classically considered higher risk patients from the outset, while the rest are only considered a risk group if they have severe congenital heart disease or severe pneumopathy, excluding asthma. A total of118 children (11%) had comorbidities  or other previous illnesses, despite these illnesses have not increased the risk of admission.

Of the 1,081 children diagnosed with covid between July 1st and October 31st, 99.2% made a full recovery. Only five had sequels, and no deaths were recorded. From now on, researchers will focus on trying to explain why some children infect other children and infect adults, but others do not transmit the virus.

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