Thread by @dgurdasani1

Interesting paper out in JID examining viral load, and viral replication in <=21 yr old children with COVID-19 in the US. TL;DR
-viral loads & virus replicability do not vary by age
-highest viral load 0-2 days after symptoms
-asymptomatic children are likely infectious too!
🧵

We often hear that children are possibly less susceptible to infection than adults, and that older children are more susceptible than younger children. Much of the evidence around this is based on flawed studies that relied on symptom-based testing.

Younger children are more likely to be asymptomatic and missed on routine testing, which is reliant on children developing symptoms, and being tested. This study compares virus loads across age groups - and among asymptomatic and symptomatic children, and mild and severe illness.

110 children were studied. Most children had asymptomatic or symptomatic mild infection. of the 110, 33 children studied had been hospitalised.

As we've seen before asymptomatic children were generally younger than those who were symptomatic. But virus load didn't differ by age. The higher asymptomaticity in younger children suggests cases will be considerably underestimated in any symptom-based testing.

Most children hospitalised were either adolescents or very young children- this is well known, and we see this in admissions in England as well. The highest risk is in under 5s, and in adolescents.

Even when viral loads were compared across ages at the same point in their illness (days of symptoms) there was no difference between children of different ages, including up to 21 year olds.

There was no difference in age distribution between those who had culture positive virus (considered to be able to replicate) and those who had culture negative virus. So replicability of the virus isolated did not differ across age groups.

When comparing different groups of children, asymptomatic & mild symptomatic infection had similar virus levels in the first 10 days of illness. Those with mild infections had higher viral loads compared to hospitalised children. Hosp adults & children had similar viral loads.

It's worrying that 8 of the asymptomatic children had culturable virus (replicating virus), which along with the high virus loads in this group would mean these children were very likely infectious, highlighting the importance of detection of asymptomatic infection in children.

Predictably the highest levels of virus were seen at 0-2 days of symptoms. This was also the period where most of the culture positive (replicable) virus was isolated, suggesting this is the most infectious period in children.

This really highlights the need to identify infection early in children. And the need to identify asymptomatic children (given this is more common in younger children and can be associated with high virus loads with replicable virus).

Unfortunately current policy in England means we're probably not stopping many chains of transmission. Given contact tracing in schools is no longer happening, we're very likely not picking up asymptomatic infection, except through LFDs, which have poor uptake with steep drops.

Asymptomatic children make 30-50% of all infections, so that's a lot of missed transmission. Many children are tested only when symptomatic (if they meet the narrow eligibility criteria for testing currently).

Unless we pick these children in the first two days, we've missed the highest risk point for transmission. Isolating them after this point may prevent some onward transmission, but will not cover the period of maximal transmission.

I hope studies like this will help convince the @RCPCH & @RCPCHPresident who've advocated for end to asymptomatic testing in children, that this is vitally important to contain transmission, reduce illness, and educational disruption. Keeping infectious children makes no sense.

Paper here by @LaelYonker et al.
academic.oup.com/jid/advance-ar…

Sorry, above tweet should read:
I hope studies like this will help convince the
@RCPCHtweets who've advocated for ending asymptomatic testing in children, that identifying asymptomatica infections is vitally important and keeping infectious children in school makes no sense.