Reinfection with SARS-CoV-2 in children

Until recent months, the 2019 coronavirus disease (COVID-19) pandemic has had the least impact on children. However, much remains to be understood about how infection with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) affects children and to what extent a previous infection protects them from re-infection.

To study: Burden of SARS-CoV-2 and protection against symptomatic second infection in children. Image Credit: Rimma Bondarenko / Shutterstock

This is all the more important as they are likely to receive the vaccine last among all groups. A new prepublication examines these questions in a cohort of children in Managua, Nicaragua.

Fund

Children mostly have mild or asymptomatic SARS-CoV-2 infection, but a few have developed severe symptoms such as shortness of breath or multisystem inflammatory syndrome (MIS-C). This is more common in younger and older children and those with co-morbidities. These are also the most at risk for post-acute COVID-19 sequelae (PASC), also known as “long covid,” although the risk is much lower than for adults.

SARS-CoV-2 infections in children have primarily been studied in the context of hospitalized children, largely missing asymptomatic and mild infections in this age group. Most of these studies have been carried out in high-income countries, which limits generalization.

An earlier study indicates that even if the sterilizing immunity wanes rapidly, the previous infection can continue at a stable level, so that the virus can become endemic. This can lead to infections eventually becoming as serious as the endemic seasonal human coronavirus infections currently in circulation. The big question is, how long will it take to happen?

Research is also underway to understand how varying degrees of disease severity relate to sequelae and subsequent protective immunity against reinfection. In addition, the impact of recently emerging variants of concern on clinical disease in children remains to be assessed. This study, published on medRxiv* preprint server, attempts to answer these questions.

What did the study show?

The study used data from the Nicaraguan pediatric influenza cohort, collected from March 1, 2020 to October 15, 2021. It was designed to be a prospective study and included nearly 2,000 non-immunocompromised children aged 0 to 14 years. .

Children with a previous infection were required to have a positive anti-SARS-CoV-2 receptor binding domain (RBD) and advanced antibody testing, or real-time confirmation of infection by amplification chain reaction. reverse transcriptase polymerase (RT-PCR) at least 60 days earlier than the current episode. All symptomatic cases had to be confirmed by RT-PCR, with a history of hospitalization within 28 days of symptom onset.

All cases were classified as subclinical, mild, moderate or severe. Those with respiratory symptoms were considered to have moderate illness, while those who required hospitalization were considered to have severe illness.

Reinfection was defined as having a positive RT-PCR test following confirmation of a previous infection by a positive enzyme-linked immunosorbent assay (ELISA) and / or a positive PCR test 60 days or more after a previous positive PCR result. All children with a positive ELISA test who showed no signs of current infection were retrospectively assessed for the severity of the infection.

In the lull period from August 1, 2020 to February 15, 2021, no case was considered COVID-19 in the absence of a clear epidemiological link with a source of infection.

In this study, half of the children were HIV positive during the study period, with around 200 PCR positive COVID-19 cases. Of these, 12 children had to be hospitalized for the disease. The incidence of the disease was highest among those under two years of age, at 16 per 1,000 person-years. This was three times higher than any other age group and twice the overall incidence of 7.7 cases per 100 person-years.

About one in five symptomatic infections has occurred in previously infected children, with a slightly higher incidence in older children. Up to the age of 5 years, 60% of children were protected against symptomatic reinfection, compared to 64% and ~ 50% in those aged 5 to 9 and 10 to 14, respectively.

All of the re-infections occurred in 2021 and were caused by the disturbing Gamma and Delta (VOC) variants of SARS-CoV-2, which began to circulate widely in this country around that time. The same trends with age were observed as in the group as a whole.

The incidence of infection in children appears to be high, with more than half of the children seroconverting during the study period. Most were mild or asymptomatic infections, but children under two had a higher risk of serious illness, five times more than children aged 5 to 9. Overall, however, only 6% developed severe disease, for an incidence of 0.4 per 100 person-years.

About a tenth of people with confirmed COVID-19 suffered from a long covid, mostly related to respiratory symptoms lasting 28 days or more. These included a runny nose, cough, and sometimes a stuffy nose or sore throat. A child under the age of 2 had rapid breathing.

What are the implications?

These results confirm previous reports that COVID-19 is less common and less severe in children than in adults. Only a small proportion of all SARS-CoV-2 infections in this age group are detected by PCR, underscoring the need for community-based prospective studies to understand the course of these infections.

The increased frequency of long covid in under 5 and older children may be due to the higher incidence of symptomatic and severe infection in these groups. The weakest protection appeared to be in children under 10 years of age. Unlike previous studies, about one in ten children with a confirmed infection had a long covid, and most had breathing problems rather than general symptoms.

The results also show that symptomatic reinfection is relatively common, accounting for more than a fifth of all confirmed infections in children. Some of them were serious illnesses. This highlights the need to monitor the severity of pediatric SARS-CoV-2 infections and a safe vaccine for younger children to prevent prolonged and severe re-infections.

*Important Notice

medRxiv publishes preliminary scientific reports which are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.