STOCKHOLM (BLOOMBERG) - Scientists in a Nordic study have found that keeping primary schools open during the coronavirus pandemic may not have had much bearing on contagion rates.

There was no measurable difference in the number of coronavirus cases among children in Sweden, where schools were left open, compared with neighbouring Finland, where schools were shut, according to the findings.

The study compares two countries that share similar societal models, including access to universal health care, but that adopted very different strategies to tackle Covid-19. Sweden avoided a proper lockdown, while Finland imposed tougher social distancing.

Indicative data show there is no difference in the overall incidence of the laboratory-confirmed Covid-19 cases in children aged one to 19 years in the two countries; contact tracings in primary schools in Finland found hardly any evidence of children infecting others, according to the working paper by the Public Health Agency of Sweden and the Finnish Institute for Health and Welfare.

Also, there is no increased risk for teachers, according to a Swedish comparison of cases among daycare and primary school staff, compared with risk levels in other professions.

It is not the first time researchers have raised questions about the merits of shutting schools during the pandemic.

A French study last month found that school children do not appear to transmit Covid-19 to peers or teachers. That investigation established that kids seemed to show fewer symptoms than adults, and to be less contagious. But the authors also said more research was needed.

Dr Hanna Nohynek, chief physician at the infectious diseases unit of Finland's health authority and a co-author of the Nordic research, said that "children get sick with Covid-19 much more rarely and less severely".

She also cautioned that more data is needed, and that "children's role in the transmission needs further study".

But for now, "it would appear that their role in transmitting Covid-19 isn't at all as big as with other respiratory infections, such as influenza," Dr Nohynek said.

After two months of remote learning, Finnish children returned to school in May, and national infection rates have continued to decline since then.

ISRAEL

But some countries have had dangerous outcomes when reopening schools, albeit for older children.

In Israel, bringing students back to the classroom accelerated the spread of Covid-19 among middle and high-school students.

Israel's example underlines how countries' varying circumstances on the ground can make all the difference, Dr Nohynek of Finland said.

"The situation in Israel is very different, with a worse outbreak in society, but also bigger classes in schools and smaller rooms", as well as larger families, she said.

Sweden's strategy for fighting Covid-19 is among the most controversial in the world. Its decision to leave much of society open, including primary schools, has coincided with a considerably higher death rate than in the rest of the Nordic region. About 95 per cent of those who have died are over 60.

Swedish health authorities say they have managed to stabilise the spread of the virus, thanks to citizens' voluntarily adhering to social distancing guidelines.

In a recent interview, Prime Minister Stefan Lofven said he remains "convinced" that his country has chosen the right strategy.