Children can develop antibodies without being infected with coronavirus, Australian study finds

Since the onset of the Covid-19 pandemic, researchers all over the world have been studying as to why the coronavirus affects the older people more while sparing kids. An interesting case study from Australia has once again reiterated this fact.  

In an unusual story, three kids in Melbourne, whose parents were Covid-19 positive, developed antibodies without even being infected with the coronavirus. 

The 38-year-old mother and 47-year-old father, developed classical symptoms such as a cough, fever and headache, two of the children only had very mild symptoms and the youngest was completely asymptomatic despite sleeping in the same bed as the parents.

The parents had caught the virus at a wedding in March this year, the early days of the pandemic and developed symptoms including a cough, congested nose, fever and headache.

However, all five members of the family had the same immune response, with antibodies specific for SARS-CoV-2, which causes Covid-19, found in blood and saliva samples of everyone. 

But despite this, none of the children ever tested positive for Covid-19 in PCR throat and nose swabs, seen as the gold-standard for detecting infection.  

Looking at this, researchers are of the opinion that children can mount a strong response against the virus once it gets inside their body which prevents it from replicating, limiting its potency. 

Children make up a tiny percentage of coronavirus cases and deaths and researchers are currently trying to find out why youngsters are less susceptible to Covid-19 than adults.  

Timeline

In March, there was no understanding of the risk coronavirus posed, no widespread mask-wearing and no social distancing.   

Seven days after the onset of the parents’ symptoms, child one (a nine-year-old boy)  developed a mild cough, sore throat, abdominal pain and loose stools.

The middle child, a seven-year-old boy, developed mild cough and coryza, a runny nose. The youngest, a five-year-old girl, had no symptoms. 

The children repeatedly tested negative for COVID-19 and displayed either no or very minor symptoms.  

Medics took samples of blood and saliva from all five family members (two parents and three children) as well as nose and throat swabs every two to three days. 

The researchers found SARS-CoV-2 specific IgA antibodies in saliva of all family members. IgA is a specific type of antibody which is secreted into the mouth, nose, lungs and gut. 

What researchers say

'Despite close contact with infected parents, PCR testing for SARS-CoV-2 was repeatedly negative in all children, who developed minimal or no symptoms,' the researchers write in their study, published in the journal Nature Communications.

'However, the children had similar cellular and SARS-CoV-2 specific antibody-mediated immune responses to their parents, suggesting that the children were infected with SARS-CoV-2 but, unlike the adults, mounted an immune response that was highly effective in restricting virus replication.'  

Scientists analysed the samples in a laboratory to decipher what type of immune response the children had and how it compared to their parents. 

Dr Melanie Neeland, who led the laboratory-based aspect of the report, said, 'The youngest child, who showed no symptoms at all, had the strongest antibody response.'

But the children had the same level of cytokine response as their parents. 

Cytokines are key chemicals in the fight against coronavirus infection. They are involved with fighting disease but they can spiral out of control, going haywire and worsening a patient's condition by attacking their own cells. 

'The discordance between the virological PCR results and clinical serological testing, despite an evident immune response, highlights limitations to the sensitivity of nasopharyngeal PCR and current diagnostic serology in children,' the researchers add.