Let’s not fool ourselves about Covid, schoolkids

What to do about schools
is perhaps the biggest dilemma facing policy makers right now. Closing them could lead to a “lost generation” of learners and make it harder for parents to get back to work. Keeping them open could further
propagate the virus. Should governments choose the latter, they will need other ways to mitigate the impact on health.
After closing down schools earlier in the pandemic, many European leaders insisted on letting students resume in-person classes after the summer break. Now with new infections on the rise again, some are having to backtrack. Italy is to switch back to distance learning, at least for high school students. Other countries may be forced to do the same.
One argument for reopening schools is that kids aren’t primary spreaders of the virus. But the evidence on this is mixed at best. There are sufficient data to show that youngsters are unlikely to fall severely ill with Covid-19. Most students who catch the virus exhibit few symptoms or none at all. Yet there is also ample research showing that even healthy carriers of Sars-CoV-2 can be infectious. As a result, children and young adults could spread the virus to older people at home, on public transportation or elsewhere.
There are two ways to decipher the role of schools in disseminating the virus. The first is a top-down approach that looks at the correlation between when schools reopened in various regions of a country and whether infections in those areas subsequently rose. Researchers can then use statistical techniques to control for other possible explanations and determine whether local governments that sent students back sooner saw an earlier surge in infections.
The evidence here is inconclusive. A study looking at Germany suggests there was no negative public health impact from schools reopening, which the researchers say was the consequence of strict hygiene measures. A separate article on Italy, however, found that schools indeed contributed to an upswing in infections. The Italian researcher suggests that the German study may have failed to capture what was going on because it used data from the summer season, when the spread of coronaviruses is generally more limited.
The second approach is to examine bottom-up studies that focus on whether kids actually carry and spread the virus. The picture here is also uncertain. The European Centre for Disease Prevention and Control published a paper in August finding that less than 5% of cases reported in the European Economic Area and the UK involved those younger than 18. That could suggest children and schools play quite a small role in transmitting infection — however, this figure probably results from children displaying fewer symptoms and therefore being less likely to be tested.
Seroprevalence studies, which search for the presence of Sars-Cov-2 antibodies in a given population to understand how many individuals were infected in the first place, find that youngsters only have a slightly smaller diffusion of the virus than adults, though these estimates are shaky. The study concludes that transmission in schools is limited but does occur — especially when the virus is circulating widely in a community. In any case, reopening schools causes important logistical problems.

—Bloomberg