During normal times, academic research moves slowly. The speed of arrival for new information on a given question – Is it healthy to drink coffee or eat broccoli? Are screens bad for children? – is quite slow. Usually we have time to think through new studies and ask what they add to what we already know.
This is not the case with COVID-19. We know very little about this disease and the virus that causes it, so each new study seems significant. And there are many new studies coming out every day – it’s hard not to feel the study’s sensory overload, and the speed makes it difficult to incorporate any information before new research comes out. The practical consequence is that people seem to take hold of every new information as if it replaces everything we saw before.
Nowhere is this more true than in the discussions about COVID-19, children, transmission and schools.
On Thursday, JAMA Pediatrics published a study that had some information about viral DNA in children’s noses. The study was widely covered, with headlines such as “New Evidence Suggesting Young Children Spread Covid-19 More Effectively Than Adults.” The general coverage was that it means that it is impossible for us to open schools. But is this really a reasonable conclusion from these data?
The issue of opening schools – if we should and what happens if we do – is a huge issue. It is about understanding the levels of transfer from the community, thinking about who will be in school and what safeguards they will take. It is about understanding how the virus is transmitted from student to student, student to adult, adult to student and adult to adult, especially in the school environment. There is a lot, a lot of evidence that we have to gather to understand this big picture.
So part of the question about the large school opening is: How much do school-age children transmit the virus if they are infected? A crucial answer to this question would affect our understanding of school openings, even if it would not even be enough to tell us what to do.
If we limit things further, part of the understanding of how many children transmit the virus is to understand the level of virus that infected children have in relation to adults. It is this question – and only this question – that this new study addresses.
To this end, these researchers studied samples from 145 people with symptomatic COVID-19. All of these people (ranging from less than a month to 65 years old) tested positive with a nasopharyngeal swab. When you test someone with a swab, the test is run through a PCR process. In this process, the viral RNA is converted to DNA and any COVID-19 viral material is tagged so that it can be recognized. The sample is then run through replication cycles to produce enough viral DNA to recognize. If the sample shows sufficient amounts of viral DNA, it is encoded as positive.
When a sample is processed, a positive result is also associated with a CT value, which measures the number of replication cycles that the machine had to perform to obtain a detectable amount of virus. A smaller CT value means that the sample started with more viral material, as it took fewer replications to produce a significant account. What the researchers found is that among the 46 children under 5 years of age, the replication time was shorter than for older children (5-17) or adults. This means that they had more viral RNA material in the nostrils.
That’s it, that’s the study.
So how do we get from this narrow information to the big questions about schools? First, can we extrapolate from viral material to infectious virus? PCR recognizes viral RNA, whether from the whole virus or fragments of the virus. In general, the presence of viral RNA indicates infectivity, but it is not exact. Fragmented or attenuated virus will appear in this test, but would not be contagious.
The second, much larger extrapolation, is from this viral material to transmission. We can speculate, but we do not really know the relationship between the amount of virus that a person carries and how contagious they are. In addition, this document is not the only data point we have about how effectively children transmit the virus. A more direct way to study transmission is to look at household transmission varies between age groups: If a 5-year-old is the first person to contract COVID-19 in his household, how many do he infect? What if a 30-year-old takes home the disease? A large study in South Korea found that children under the age of 10 transmit at a slower rate than other groups (about five percent of their household contacts were infected, compared with 11 percent in total). This study suggests that younger children are not effective spreaders. Another, smaller study of 14 children under the age of 14 in Italy (not yet peer-reviewed) showed transmission to 22 percent of household contacts. These two results are somewhat in contrast to each other, but since the South Korean study is larger, better documented and has been peer-reviewed, I think right now we would benefit from their evidence.
We want to think about this proof test in the water in connection with more direct information about transmission and honestly I think we should privilege evidence for direct transmission.
The last step is to ask how this speaks to schools and here it seems to be a very big leap. Among other things, the higher amounts of viral material are seen in this study in children under 5 years, which is below school age. But beyond that, assuming 6-year-olds show the same high levels when they get sick, this is just a small, small piece of the reopening puzzle. If a study had found that children under the age of 5 had no viral material, it would not have made the school opening safe. And finding that they have a lot does not add much to our understanding of its risks.
Of course, there is value in new evidence, in research. We need to continue to learn more about the virus and this document will help us do that. But at the same time, we must be careful about how much we draw from a given study. And this one does not tell much about the school opening.
Future Tense is a partnership between Slate, New America and Arizona State University that explores new technologies, public policy and society.