Interim results from a prospective cohort study of households in Utah and New York City found that kids had similar rates of Covid-19 infection compared to adults—but they were less likely to show any symptoms, researchers found.
In the early days of the Covid-19 pandemic, kids seemed to account for a minority of cases, leading to the widespread assumption that children were less susceptible to the virus than adults. But as the pandemic wore on, seroprevalence, household, outbreak, and surveillance data confirmed that kids are, in fact, vulnerable to SARS-CoV-2.
“Most studies that have drawn inferences about risk among children versus adults lacked systematic, longitudinal testing for both asymptomatic and symptomatic infections or relied on serologic markers of infection that may not always be present or sustained after asymptomatic infection,” Fatimah S. Dawood, MD, of the CDC in Atlanta, and colleagues wrote in JAMA Pediatrics. “Both limitations might lead to underdetection of SARS-CoV-2 infection cases among children and the false conclusion that risk of infection is lower among children than adults.”
For their analysis, Dawood and colleagues pulled interim data from the prospective Coronavirus Household Evaluation and Respiratory Testing (C-HEART) study—which follows households with one or more children 17 years of age or younger in Utah and New York City—to estimate Covid-19 infections among kids and adults, estimate household infection risk, and compare clinical features of infection according to age during a period of increased SARS-CoV-2 circulation (September 2020-April 2021).
“Adults and children of all ages had similar risks of SARS-CoV-2 infection, but approximately half of SARS-CoV-2 infections among children were asymptomatic compared with a much smaller fraction among adults,” they found.
Notably, fever was an infrequent symptom in both children and adults, suggesting that fever-based Covid screening is likely to miss a substantial number of cases.
“It remains unclear how risk of SARS-CoV-2 infection among adults and children will evolve with increasing Covid-19 vaccine uptake among adults and increasing circulation of SARS-CoV-2 variants of concern,” they wrote. “Our findings suggest that SARS-CoV-2 infection prevention strategies, such as handwashing, masking, physical distancing, and Covid-19 vaccination should target children in addition to adults to both mitigate individual health outcomes for children and reduce the overall burden of SARS-CoV-2 infection in the community.”
In an editorial accompanying the study, Flor M. Munoz, MD, of Baylor College of Medicine in Houston, agreed with the study authors, writing that these findings “have substantial implications for decision-making in regard to return-to-school planning and the participation of children in various group activities, including childcare, after-school programs, and camps… it is likely that as SARS-CoV-2 establishes itself as a respiratory human pathogen, outbreaks associated with participation of children in childcare, school, and other group activities will continue to occur and contribute to the perpetuation of this virus as a threat to communities in the United States and worldwide, especially where children and other populations remain unvaccinated.”
Munoz also urged early inclusion of kids in vaccine studies and vaccination strategies, as well as inclusion in studies of preventive treatments, including monoclonal antibodies, antivirals, and other potential therapies for Covid-19.
“The delay in initiating such studies and subsequent paucity of data to support the use of vaccines and therapeutics has resulted in delays in the development of evidence-based guidance for the care of children with Covid-19,” she wrote. “This is painfully apparent today, as the Delta variant continues to ravage through vulnerable populations, unvaccinated individuals, and young individuals, children included.”
For this study, the study authors enrolled households with at least one child (age 0-17 years) from New York City and selected counties in Utah, including Salt Lake, Weber, Davis, Box Elder, Cache, Tooele, Wasatch, Summit, Utah, and Iron county. The C-HEART study used a convenience sample approach “to allow for rapid cohort enrollment from previous cohort studies and the broader community,” they explained. Participants were enrolled from August 2020 to February 2021, and SARS-CoV-2 surveillance took place from September 2020 to August 2021—this analysis only included the results of surveillance conducted as of April 15, 2021.
Once a week, participants were asked to self-collect midturbinant flocked nasal swabs for reverse transcription-polymerase chain reaction testing—regardless of whether they had symptoms—and complete questionnaires assessing symptoms. Adult caregivers collected samples for children who were unable to complete the nasal swab themselves. Participants were asked to self-collect three additional specimens in the event that they developed Covid-19–like illness.
The primary study outcome was incident cases of any SARS-CoV-2 infection, including both asymptomatic and symptomatic infections. The study authors also assessed “the asymptomatic fraction of infection calculated by dividing incidence rates of asymptomatic infection by rates of any infection, clinical characteristics of infection, and household infection risks.” All primary outcomes were compared by participant age group, they added.
The study cohort consisted of 1,236 individuals from 310 households, of whom 176 (14%) were ages 0-4 years, 313 (25%) were ages 5-11 years, 163 (13%) were ages 12-17 years, and 584 (47%) were ages 18 years and older.
Dawood and colleagues found that overall SARS-CoV-2 incidence rates were 3.8 (95% CI: 2.4-5.9) and 7.7 (95% CI: 4.1-14.5) per 1,000 person-weeks in the Utah and New York City cohorts, respectively.
Also among the findings:
- “Site-adjusted incidence rates per 1000 person-weeks were similar by age group: 6.3 (95% CI, 3.6-11.0) for children 0 to 4 years, 4.4 (95% CI, 2.5-7.5) for children 5 to 11 years, 6.0 (95% CI, 3.0-11.7) for children 12 to 17 years, and 5.1 (95% CI, 3.3-7.8) for adults (≥18 years).
- “The asymptomatic fractions of infection by age group were 52%, 50%, 45%, and 12% among individuals aged 0 to 4 years, 5 to 11 years, 12 to 17 years, and 18 years or older, respectively.
- “Among 40 households with one or more SARS-CoV-2 infections, the mean risk of SARS-CoV-2 infection among all enrolled household members was 52% (range, 11%-100%), with higher risks in New York City compared with Utah (80% [95% CI, 64%-91%] vs 44% [95% CI, 36%-53%]; P<0.001).”
Dawood and colleagues noted that this last finding of higher household infection risk in New York City versus Utah “may be attributable to differences by site in household crowding or preventive behaviors, community transmission of SARS-CoV-2, or circulating virus lineages.”
The study authors concluded that their findings underscore an urgent need for rapid evaluation of Covid-19 vaccine efficacy for kids, as well as more thorough analyses of the risk posed by asymptomatic transmission. And they may see some progress on the former point in the next month or so—the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) is slated to discuss the viability of authorizing the currently approved BNT162b2 vaccine for use in children ages 5-11 years, based on phase III data from the manufacturer suggesting the vaccine offered a comparable immune response to that seen in adults when administered in this younger age group, even when given at a lower dose. That VRBPAC meeting is currently slated for Oct. 26.
Dawood noted a number of limitations to their analysis, including that individuals who are willing to participate in a study that requires such intensive follow-up likely have a better attitude toward public health and science than the general population, which may influence behaviors associated with infection risk. They also noted that persons of certain racial backgrounds and low-income households were underrepresented in the analysis, and that it is possible that some illness symptoms experienced by children with Covid-19 went unidentified due to symptom information being relayed by adult caregivers.
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Interim results from a prospective cohort study of households in Utah and New York City found that kids had similar rates of Covid-19 infection compared to adults, but kids were far more likely to be asymptomatic.
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These findings suggest Covid-19 mitigation strategies should target children in addition to adults, and children should be included in trials for Covid-19 vaccines and treatment.
John McKenna, Associate Editor, BreakingMED™
Study coatuhor Porucznik reported personal fees from McKesson Corporation outside the submitted work. Coauthors Porucznik, Stanford, Stockwell, Hunt, Jeddy, Altunkaynak, and Kattel reported funding for this study from the US Centers for Disease Control and Prevention through contract 75D30120C08150 with Abt Associates. Coauthor Meece reported contract funding from the Centers for Disease Control and Prevention.
Munoz reported grants from Pfizer (paid to their institution for a vaccine study) and is a data and safety monitoring board member of Moderna (various vaccines including COVID-19), Pfizer (respiratory syncytial virus vaccines), Virometix (respiratory syncytial virus vaccines), and Meissa Vaccines (respiratory syncytial virus vaccines) during the conduct of the study, as well as grants from Gilead Sciences (paid to their institution for a study on pediatric remdesivir) outside the submitted work.
Cat ID: 138
Topic ID: 85,138,730,933,190,926,138,192,927,151,928,925,934
