Study: Children Are Less Likely to Produce Antibodies Against COVID-19 Than Adults

A child receives antibacterial gel as in person lessons return amid the COVID-19 pandemic on February 17, 2022 in Quito, Ecuador.

Franklin Jacome / Agencia Press South / Getty Images

Key Takeaways

  • Children with mild COVID-19 are less likely to produce antibodies than adults, despite having a similar viral load and symptoms, a new study finds.
  • There was no significant difference in antibody levels in children with symptomatic and asymptomatic COVID-19.
  • Children may have a robust initial immune response that clears the infection more quickly and nixes the need for specialized antibodies, but a lack of antibodies may leave them more vulnerable to reinfection.

Children are less likely to produce antibodies from a mild COVID-19 infection compared to adults who have similar symptoms and viral load, according to a new study.

The study, published by Australian researchers in JAMA Network Open last week, is one of the first to measure how well children mount an immune response to a COVID-19 infection.

The study group included 57 children with a median age of 4 and 51 adults with a median age of 37, who tested positive for COVID-19 between May and October 2020. All the participants had either mild symptoms, such as cough and fever, or had no symptoms.

The researchers checked the participants’ COVID-19 DNA using nose and throat swabs, as well as their blood samples, to measure the level of immunoglobulin G (IgG) antibodies. IgG is the most prevalent antibody in humans and it can indicate an individual’s immunity to certain pathogens.

When the COVID-19 virus enters the body, it is first met with the innate immune system, the body’s first line of defense against pathogens. This immune response is supposed to ward off viruses until the adaptive immune system builds a longer term immunity with T cells and antibodies.

When the virus thwarts this initial barrier, it triggers immune cells to produce antibodies that are specific to the COVID-19, such as IgG antibodies that target the spike protein.

The researchers found that only 37% of children produced antibodies, compared to 76% of adults. Each group had similar viral loads and factors like age and sex didn’t seem to impact individuals’ antibody levels.

Children are usually thought to have a more robust innate immune response, but this study didn’t find any differences between the responses in children and adults, likely due to the small sample size.

“The current view is that children have more robust innate immune systems which enables them to clear the virus more efficiently than adults,” said Paul Licciardi, PhD, associate professor at the Murdoch Children’s Research Institute in Melbourne, Australia and coauthor of the study.

The rapid clearance of the virus may mean that the virus had less time to engage with other parts of their immune system, Licciardi said. This may mean that children are less likely to produce antibodies against COVID-19 and therefore more vulnerable to reinfection.

How Do Pediatric and Adult Immune Responses Differ?

Scientists have long known that children tend to have more reactive innate immune responses.

An analysis by researchers in the United Kingdom found that children mount a stronger and faster response to COVID-19 infection than adults. Particularly in young children, the innate immune system kicks in quickly to clear the virus, often preventing it from getting as deep into the body as it might in adults.

Adults produce a broader set of antibodies including more virus-blocking ones than children, according to a study from researchers at Columbia University last year. Even children who developed multisystem inflammatory syndrome (MIS-C) from severe COVID had a reduced neutralizing antibody response compared to adults who were never hospitalized for COVID-19. 

Adults who had symptomatic COVID-19 in the Australia study had 3-times higher IgG levels than asymptomatic adults. But between asymptomatic and symptomatic children, there was no significant difference.

How Well Protected Are Children Against Reinfection?

Even when the Australian researchers noted similar levels of COVID-19 viral load in each cohort, the antibody response was observed in about half as many children as adults.

Plus, these children tended to have lower levels of certain kinds of antibody-producing memory B and T cells than their adult counterparts. A lack of these long-term immune cells could potentially leave them vulnerable to reinfection.

“Generally, if there is no evidence of an antibody response, there may be a risk of being reinfected,” Licciardi said. “However, we should not discount other parts of the immune system that can also respond to the infection.”

For instance, cellular immunity, which doesn’t include antibodies, may play a key role. Children may also have a more robust response from the immune cells in the mucosa of the respiratory tract.

And while the adaptive immune response may not have been triggered in many children with mild COVID-19 in this study, Licciardi said that doesn’t mean their immune response is inadequate.

Implications for COVID-19 Surveillance

To estimate how many people in a study group have been sick with COVID-19, researchers often test for antibody levels. The authors of the Australia study said that because many children may not have detectable antibody levels after being sick, testing for these proteins may be a somewhat unreliable indicator of vaccination and prior COVID-19 infection.

“If only around a third of children have evidence of SARS-CoV-2 specific antibodies after a confirmed infection (as in our study), this will not be a reliable measure of infection,” Licciardi said.

Antibodies are only part of the immune response and other markers, such as the presence of T cells, may better indicate viral exposure in both children and adults.

This study only accounted for individuals who were infected with the original COVID-19 strain. Preliminary data suggests children infected with Delta have higher antibody levels, Licciardi said, and the same is likely true for those sick with Omicron since both variants are associated with higher viral loads.

Further research will help scientists better understand how children mount antibody responses to more recent variants. In the meantime, Licciardi said, vaccines remain the most effective way to stimulate an immune defense system in children and prevent outcomes like long COVID.

What This Means For You

Children may be less likely to develop long-lasting protective antibodies against COVID-19 after infection. Vaccination is still the best way to protect children from COVID-19 infection and outcomes like long COVID.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Yoshida M, Worlock KB, Huang N, et al. Local and systemic responses to SARS-CoV-2 infection in children and adults. Nature. 2022;602:321–327. doi:10.1038/s41586-021-04345-x

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By Claire Bugos
Claire Bugos is a health and science reporter and writer and a 2020 National Association of Science Writers travel fellow.