This is a shortened version of an article by microbiologist Siouxsie Wiles and paediatrician Jin Russell that appeared in The Spinoff last week. Hopefully, it may be useful to some.

As kids return to school for the first time under Orange microbiologist Siouxsie Wiles and paediatrician Jin Russell share the latest research on staying safe in the classroom.

School students in Aotearoa New Zealand are heading back to class this week. With the country being at Orange, masks are no longer mandatory in educational settings. To help everyone understand what to expect in the coming weeks and months, we thought it might be useful for us to explain what the evidence is saying about Covid-19 and schools.

The US Centers for Disease Control (CDC) website has a regularly updated summary of scientific studies of Covid-19 transmission in schools. This Evidence Brief identifies four major factors that impact the amount of Covid-19 in schools. We’re going to go through these four factors below to explain why Covid-19 in schools is more dynamic and variable than most news headlines suggest.

First, though, we want to be really clear: schools and ECE are essential services for children and their whānau. Alongside formal education, they are settings for friendships, connection, a sense of belonging, books and resources, sports, kapa haka, and much more. Some young people thrive with remote learning, but many others struggle. Overseas data shows that students from disadvantaged homes can fall behind when schools are closed and struggle to catch up again, harming their long term prospects. Schools are the places where students with learning difficulties can receive extra educational support, and where some students with disabilities see their therapists. Importantly, schools form part of the social security net, with counsellors, nurses, social workers, and safe adults, to support children and young people who face challenging circumstances at home.

That’s why we think it’s important that schools stay open as much as possible during the pandemic. And because there are teachers, children, and families in our community who are more medically at risk from Covid-19, schools need to be safe and inclusive for everyone.

The four factors that impact Covid-19 within schools

Factor one: Community incidence

The first factor that impacts the level of Covid-19 within schools is how much Covid-19 there is in the local community. This is intuitive. When there are many infections in the community, more infected students and staff may come to school. When there are fewer cases in the community, fewer infected people will be at school. The point is this: transmission in schools is dynamic. It varies based on the context. This is where we need to dispel the first unhelpful narrative that schools are super-spreader environments.

Epidemiologists at the National Centre for Immunisation Research and Surveillance (NCIRS) in Australia have been carefully tracking Covid-19 transmission in schools in New South Wales throughout the pandemic. In their latest study, the proportion of close contacts who tested positive for Covid-19 after exposure at school, also known as the “secondary attack rate”, was 2.4% for delta, and 3.7% for omicron. This means that for every one infected student or staff member who came to school with omicron, 3.7% of their close contacts went on to test positive for Covid-19 due to transmission at school.

The NCIRS school studies are useful for Aotearoa New Zealand because we have similar vaccination rates and Covid-19 strategies in schools to New South Wales. The NCIRS studies are also very reliable because close contacts are followed up with PCR testing regardless of whether people had symptoms or not. This is important for accuracy because children often don’t have symptoms so can go undetected.

It’s clear that the risk of spread within classrooms can be kept low compared to other settings – for instance, secondary attack rates in households in the same NCIRS study were over 60%. This is why you may have heard schools being described as “lower risk settings”.

While the risk of onward transmission can be kept lower compared to other settings, it is clearly not zero risk. This brings us back to the idea that the level of Covid-19 in the local community matters. We need to dispel the second false narrative, that schools are low-risk environments no matter what. If there is a lot of Covid-19 in the community, there is a greater risk of spread within schools. Each infected person coming to school poses a small but cumulative risk of onward spread to others.

The good news, however, is that when the right strategies are in place, schools can do remarkably well at stopping most chains of transmission. Let’s look more closely at these strategies now.

Factor two: Taking a multilayered approach to preventing Covid-19

Improving ventilation in classrooms, using portable HEPA air cleaners where needed, mask-wearing, good hygiene, and cohorting students into groups to prevent a lot of mixing are all part of the toolkit. Lots of testing in the community also helps. Every person who stays home when they have Covid-19 snuffs out a potential chain of transmission. When community case numbers are high, the more layers of protection, the better.

Clean, fresh air is a key layer of the strategy. Focusing on better ventilation is smart – it reduces the risk of spread for not only Covid-19, but other viruses as well, and protects everyone in a space without any inconvenience. The Ministry of Education has developed guidance for schools to improve ventilation in conjunction with indoor air quality experts. If we can improve ventilation in schools, we’re likely to see tremendous gains in child health which will last beyond the pandemic.

Factor three: Immunity from vaccination and infection

The third factor that affects Covid-19 in schools is how much immunity is in the school community – from vaccination and from infection. We would much rather that people got their immunity from being vaccinated, rather than from infection!

While it is true that being vaccinated doesn’t guarantee that a person won’t catch Omicron, being triple vaccinated can reduce transmission. At the moment, just over 70% of people who are eligible are boosted, and younger and middle-aged adults have lower levels of booster coverage than older adults. If all the parents and adults connected to schools who are eligible got boosted, this would protect them from Covid-19 and help reduce transmission in the community, and by extension, in schools.

Factor four: The circulating variant(s)

The final important factor is the Covid-19 variant(s) circulating in the community – what are the symptoms, how well does it transmit, and how well do the different public health measures work to reduce transmission? The virus is evolving. While Delta was different to previous versions of the virus, the vaccines were really effective at stopping people from getting infected in the first place.

Omicron is different from Delta and while vaccines are still preventing serious illness, they aren’t doing as good a job at preventing transmission. But how might the virus be evolving right now? And what might the next variant be like? Omicron is not “mild”. We’ve just got better at preventing and treating Covid, at least in the short term. But it’s still deadly. And that doesn’t factor in the potential long term consequences of infection. People also need to understand that it’s not “one and done”. There are people who are now who have had Covid multiple times.

So what should we expect to happen in schools in the weeks and months ahead?

We’ve laid out the four factors that impact Covid-19 in schools, and shown that the evidence is really clear that schools can be kept open safely even when cases of Covid are high in the community. What is required to achieve this is a commitment to having strong layers of protection in place, especially if and when case numbers start to rise again.

In the first 18 months of the pandemic, Aotearoa New Zealand topped the OECD for the number of days schools were fully open. While students were shut out of school for long periods overseas, our young people were reaping the benefits of our bold, collective action. We know what protections make for better outcomes for everyone. We need to put them in place and keep acting collectively. That’s how we will do the best for children.

On My Walk

Episode 4