This is a summary, written by members of the CITF Secretariat, of:

Bhatt M, Zemek RL, Tang K, Malley R, Plint AC, Pham-Huy A, Dawson J, McGahern C, Pelchat M, Arnold C, Galipeau Y, Langlois MA. Antibody Seronegativity in COVID-19 RT-PCR-Positive Children. Pediatr Infect Dis J. 2022 May 9. doi: 10.1097/INF.0000000000003573.

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

Published in the Pediatric Infectious Disease Journal, this CITF-funded study led by Dr. Marc-André Langlois, along with Malaa Bhatt, Roger Zemek (University of Ottawa) found that approximately 1 in 8 individuals with COVID-19 did not develop antibodies detectable in blood serum (a process known as seroconversion) as a result of infection. Children, particularly the youngest, were approximately half as likely to seroconvert compared with adults. The paper also points out that the absence of fever/chills was the only strong symptomatic predictor of an inability to create antibodies.

Key findings

  • Most individuals who were positive for COVID-19 by PCR test (287 of 330) seroconverted.
  • Of the 43 individuals (13%) who did not seroconvert, 63% (27/43) were children (median age was 12-years-old).
  • All hospitalized participants (10/330, 3%) did have an immune response to infection.
  • Children up to the age of 4 had lower odds of seroconversion than older children (aged 5-17) and adults (>18 years old). Odds of seroconversion increased with age.
  • Individuals who were asymptomatic at the time of RT-PCR testing were no more or less likely to seroconvert.
  • Seroconversion was not associated with time since infection (≤30 vs >30 days).
  • The number of reported symptoms was not associated with seroconversion. However, the presence of fever/chills was associated with increased rate of seroconversion.

Theoretically, memory B-cells and T-cells may contribute to protection against coronavirus disease even in the absence of circulating antibodies. Having a natural infection does not diminish the recommendation for widespread vaccination and highlights the need for public health messaging that informs populations that the development of antibodies, and possibly of immunity, cannot be assumed after a symptomatic infection.

This study was a part of the prospective case-ascertained study of household COVID-19 transmission in Ottawa. The study collected participant samples from September 2020 to March 2021 and investigated the SARS-CoV-2 RT-PCR–positive individuals that did not seroconvert and factors associated with non-seroconversion. The study included 330 RT-PCR positive participants- 162 children (median age of 8.9 years) and 168 adults (median age of 40.7 years). Vaccinated individuals were excluded from the study.