Science

As Victoria and NSW plan school reopenings, experts are highlighting the risk of Covid-19 transmission to unvaccinated children posed by poor ventilation systems. By Manuela Callari.

Covid-proofing classrooms

Students are returning to schools in NSW and Victoria this month, but those aged under 12 are not yet eligible for Covid-19 vaccinations.
Credit: Daniel Pockett / Getty Images

Children in Victoria and New South Wales will make a staggered return to face-to-face learning from the second half of October, although hundreds of Covid-19 cases are still being recorded every day in the two states.

The Delta variant of SARS-CoV-2, thought to be up to 90 per cent more infectious than the original Alpha strain, is causing record numbers of hospitalisations among children in the United States. NSW recorded a fivefold increase in the spread of Covid-19 in schools with the Delta outbreak.

It remains unclear whether the high numbers of children with Covid-19 needing hospital care are due to Delta’s increased transmissibility, or high vaccination rates among adults, or whether this variant causes more severe disease in children, as it does in adults.

While most children still only experience mild to no symptoms, they are more likely to transmit the Delta variant than previous strains. So, as pupils return to mingle in the classroom, what can be done to make schools Covid-19 proof?

In Australia, children 12 and over are eligible to receive a Covid-19 vaccine, but most will not be fully vaccinated by mid-October. A vaccine for children under 12 might be approved in coming months, but younger kids will remain unvaccinated for now.

The American Centers for Disease Control and Prevention advises creating a protective cocoon for unvaccinated children by vaccinating the adults around them. That means making sure all teachers, school staff and parents have been vaccinated.

“Vaccination remains a critical safety element,” says Associate Professor Asha Bowen, a paediatrician at Perth Children’s Hospital and head of Skin Health at the Wesfarmers Centre of Vaccines and Infectious Diseases at the Telethon Kids Institute.

NSW and Victoria have now mandated vaccination for all school and preschool staff.

Mask-wearing in older children can also successfully curb the spread of the virus. Current lockdown rules require anyone aged 12 years and over to wear a face mask in indoor and outdoor public spaces, including schools. Some schools have recommended all students wear a face mask at all times at school. But for anyone younger than 12, wearing a face mask might do more harm than good.

“Most young children might be able to cover their cough, but many won’t be able to wear a mask and take it on and off and not touch it,” says Bowen. “I don’t think that asking children who are not familiar with wearing masks to wear one is a particularly useful part of the strategy.”

SARS-CoV-2 spreads through the air. The virus is emitted through the nose and mouth of an infected person when breathing, speaking, sneezing and coughing and is carried by microscopic particles called aerosols that can linger in the air for hours.

Classrooms with poor ventilation are a high risk for transmission. “Schools are perfect grounds for respiratory infections,” says Professor Lidia Morawska, director of the International Laboratory for Air Quality and Health at the Queensland University of Technology.

Most government schools are naturally ventilated. They are not equipped with engineered mechanical ventilation systems but rely on opening windows to introduce fresh air into the classrooms. Geoff Hanmer, an architect and adjunct professor of architecture at the University of Adelaide, says to satisfy the National Construction Code, a school must have a certain number of windows in proportion to a room’s floor area. But there is no compunction to have them open.

He says in many cases, particularly in older schools, windows have been painted or screwed shut as they risk falling to pieces. “That means that there are many schools that have very unsatisfactory ventilation.”

In warmer months, airconditioning systems are turned on. But the most common types, Morawska says, recirculate air rather than introducing fresh air into the classroom, potentially making things worse. “The concentration of the virus in these non-ventilated classrooms builds up,” she says.

Hanmer and Morawska agreed short-term solutions can be quickly and easily implemented without a huge cost.

“The first step is awareness of the problem,” says Morawska. Before this pandemic, she says, the importance of air quality was completely neglected while policies predominantly focused on thermal comfort and water quality in buildings.

Assessing classrooms’ air quality is crucial. “Unless we measure, we won’t know because just by looking at the room, you can’t tell whether it’s well ventilated or isn’t,” Hanmer says.

A good proxy for ventilation is the concentration of CO2 students breathe out throughout the day. A nondispersive infrared CO2 monitor, which costs less than $100, can quickly and accurately measure CO2 concentration. A concentration lower than 800 parts per million (ppm) of CO2 indicates the environment is well ventilated.

If appropriate ventilation can’t be achieved naturally, a portable high-efficiency particulate-absorbing (HEPA) air purifier can reduce the amount of virus in the air. But these should be the last resort, says Morawska. They cost up to $900 each and one device is needed per classroom, and they have high running costs.

Last, moving classes to outdoor spaces as the weather gets warmer can also be an easy option.

The federal government has largely ignored the airborne nature of SARS-CoV-2, with little done to assess and improve ventilation in schools. “It’s much easier for the government to recommend something that puts the responsibility on individuals, like mask-wearing, than to do something on ventilation, which requires them to take some more actions,” says Morawska.

Besides the more accessible short-term solutions, she says, the federal government must develop guidelines and policies around air quality to inform the engineering and construction of new buildings.

Last month, the Victorian government announced a $190 million package to assess classroom safety and purchase 51,000 purifiers to be installed into government and low-fee Catholic and independent schools. “This is very progressive,” Morawska says.

The NSW Education Department only recently began an audit of school classrooms to assess the condition of windows. “It’s a good start,” says Hanmer.

“I think we’re talking about a bit of a moment in time here,” says Hanmer. He compared the wake-up call on air quality to when English physician John Snow discovered cholera was waterborne in the late 19th century. All Snow had to do was remove the handle from a water pump in Broad Street in London to stop people drawing water from the infected well and catching the deadly disease.

“We’ve now come to the same point with airborne diseases,” Hanmer says. “We accept that people get colds and flu, but we don’t need to because we could control that by making sure that people have access to clean air. It’s not just for pandemics. It’s for all respiratory diseases.”

Young children remain the last group of unvaccinated people in Australia. From the overseas experience, it is evident that the virus quickly moves towards the unvaccinated.

“We need to do everything we can to stop that happening,” says Hanmer. “Although children have less serious disease in most instances, if you have a very large number of children, we’re talking about four million children [in Australia], then a significant number of them will get very sick. A small percentage of the large number is still quite a large number.”

“The classroom is the best place for children to learn,” says Asha Bowen. She says lockdowns and online learning have disrupted both education and social interaction. Making classrooms Covid safe is essential for uninterrupted face-to-face learning. “[The school] is the most supportive environment possible for children of all abilities to be educated and flourish.” 

This piece was produced in collaboration with cosmosmagazine.com.

This article was first published in the print edition of The Saturday Paper on Oct 9, 2021 as "Covid proofing".

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Manuela Callari is a freelance science writer.