Kids hard-hit by Delta; which ART performs best?

That COVID-19 mostly spared children might be changing. The Delta variant has taken a severe, unthinkable toll on kids – at least in Arkansas, US, reports an expert at IDWeek 2021.

Hospitalizations and other indications of severe disease increased significantly during the July 2021 peak, according to Dr Michael Cima, state epidemiologist, Arkansas Department of Health, Arkansas, US. “This suggests that the Delta variant is not only far more infectious than the next most infectious variant of concern. It is also potentially more virulent.”

In fact, the Delta variant was the dominant circulating SARS-CoV-2 strain in Arkansas in June and early July, he added. (IDWeek 2021, abstract LB10]

Cima and team reviewed hospitalization data and ICU use, including mechanical ventilation and multisystem inflammatory syndrome, in children with 3-month records as inflection points during the pandemic.

Paediatric COVID-19 cases numbered 3,268 in July 2020. It spiralled to 11,735 in January 2021 and 8,031 in July 2021. Despite nearly 32 percent fewer cases in July 2021 than in January, there were 42 percent more hospitalizations (105 vs 74), 69 percent more ICU admissions (18 vs 11), and a 300-percent increase in mechanical ventilation use among children, Cima pointed out.

Interestingly, neutralizing antibodies remained detectable 6 months after COVID-19 infection among children in another study. [IDWeek 2021, abstract LB9]

“When we looked across the entire cohort, there was a large degree of variability in the neutralization titres that we measured for each individual,’” said presenting author Ms Lauren Gentles, PhD candidate from the Fred Hutchinson Cancer Research Center in Seattle, Washington, US. “Overall, we saw variable trajectories by individuals. But when we looked at an aggregate and the difference between the neutralization titres measured for the first sample and the second sample collection, there was no significant difference.”

“This suggests that the neutralization titres are maintained over 6 months post-COVID-19 infection in children,” she added. “These findings are interesting because they represent the functional antibody neutralizing response, and its kinetics, as well as the binding antibodies.”

Most frequently reported COVID-19 antigen test

In terms of COVID-19 diagnostics, the Panbio test by Abbott was the most frequently reported COVID-19 antigen rapid test (ART) in a recent bivariate meta-analysis of 12 different ARTs based on 119 datasets and 71,424 tests performed. [PLoS Med 2021;18(8):e1003735]

Across these, the pooled estimates of sensitivity and specificity on all samples were 72.1 percent and 99 percent, respectively. Looking at Panbio alone, the pooled sensitivity was 71.8 percent (95 percent confidence interval [CI], 65.4-77.5), based on 39 (18.2 percent) datasets and 28,089 (25 percent) tests reported. The COVID-19 Ag Respi-Strip had the lowest pooled sensitivity of 40 percent of all ARTs rapid tests evaluated.

The ARTs performed better at detecting SARS-CoV-2 in patients with increased viral loads, when used within the first week from symptom onset rather than after 1 week, and when used as directed by manufacturers.

In a subgroup analysis, pooled sensitivity was higher among test samples with a cycle threshold (Ct) value of <25 (95.8 percent) vs samples with a Ct value of ≥25 (50.7 percent).

Symptomatic patients had a markedly increased pooled sensitivity than asymptomatic patients (76.7 percent vs 52.5 percent).

Interestingly, Panbio also had a higher sensitivity (82.9 percent) than the Standard Q and Sofia rapid antigen tests (81 percent and 80.4 percent, respectively) in another study. [J Clin Virol 2021;137:104785]

What the findings mean

As children were not spared by Delta, the push for vaccine jabs in the young is gathering steam. Given that ARTs detect the vast majority of patients within the first week of symptom onset, including those with high viral load, “ARTs have high utility for diagnostic purposes in the early phase of COVID,” said the researchers.

“The accuracy achieved by the best-performing ARTs, combined with the rapid turnaround time, suggests that these rapid, simple tests could have a significant impact on the COVID-19 pandemic if applied in thoughtful testing and screening strategies,” they added.