Children’s Duration of COVID-19 Immunity from Natural Infection

Though initially believed to be exempt from the worst of the COVID-19 pandemic, we now know that children contract COVID-19 at similar rates as adults. In December 2021 and January 2022, COVID-19 infections among children spiked when the highly transmissible Omicron variant became the predominant strain. Children’s infections, hospitalizations, and deaths rose at rates unprecedented in the coronavirus pandemic.

One study, published this week in Pediatrics, sought to determine the incidence and longitudinal presence of natural antibody response from COVID-19 infection. Due to the prioritization of testing adults and immunocompromised persons earlier in the pandemic, antibody response in the pediatric population is largely unknown.

The ongoing Texas Coronavirus Antibody Response Survey (Texas CARES) is a prospective population-based seroprevalence endeavor to assess COVID-19 antibody status over time. This study included Texas CARES participants 5-19 years of age, who completed 3 antibody assessments throughout a 6–8-month period. Demographic information and COVID-19 infection-related symptom status were determined via questionnaire.

The study included 218 Texas CARES participants, the average age of whom was 12.8 years. Of the 34.4% of the sample who had nucleocapsid antibodies at the baseline assessment, 96% of them maintained these antibodies 6 or more months later.

Notably, there was no difference in antibody presence by symptom status (i.e., symptomatic versus asymptomatic infection) or illness severity (mild-moderate vs severe). Antibodies also did not differ by sex, age, or body mass index throughout the 3 antibody measurement periods.

The investigators conducted a sensitivity analysis to test for differences between participants who completed all 3 antibody assessments and participants who did not. The only significant demographic variable was ethnicity; Hispanic participants were more likely to have completed all 3 assessments than non-Hispanic white participants.

The results showed that the majority of children and adolescents retained preexisting COVID-19 antibodies for at least 6 months after natural infection. The investigators noted that 57.9% of the children in the cohort were negative for infection-induced antibodies at the third assessment, suggesting a large number of children and adolescents are still lacking natural immunity to COVID-19. Therefore, they wrote, “vaccines have an important role to play in providing protection against COVID-19 for children aged 5 years and older, and for those < 5 years as they become eligible.”

In a statement, corresponding author Sarah Messiah, PhD, MPH, elaborated on the findings. “Adult literature shows us that natural infection, plus the vaccine-induced protection, gives you the best defense against COVID-19. There has been a misunderstanding from some parents who think just because their child has had COVID-19, they are now protected and don’t need to get the vaccine. While our study is encouraging in that some amount natural antibodies last at least six months in children, we still don’t know the absolute protection threshold. We have a great tool available to give children additional protection by getting their vaccine, so if your child is eligible, take advantage of it.”