Some face masks could be worse than nothing if they lull people into a false sense of security, experts say.

With Omicron knocking at New Zealand's door, scientists are urging people to ditch face coverings that don't offer protection and think about filter, fit and consistent proper use.

'Those stretchy single layer masks you see around are completely ineffective,” says Dr Lucy Telfar Barnard, a senior research fellow in public health from the University of Otago.

Any mask is generally better than no mask, she says, but if using a substandard mask is stopping you get something better, 'then it's counterproductive”.

Dr Joel Rindelaub, a research fellow at the University of Auckland, says plastic face shields and mouth shields were 'effectively worthless”.

'[They] are essentially not going to do anything to prevent aerosol transmission.”

N95 and P2 masks offer the best protection, experts agree, and they're available at hardware stores and pharmacies. If you can't access or afford one, a surgical mask adjusted to fit well is the next best thing, Telfar Barnard says.

That might mean using a mask bracket that keeps the material off your face, knotting the ties behind your ears and tucking the pleats, or wearing a well-fitting cloth mask over the top. You can also cut down a surgical mask to use as a filter in a cloth mask.

She urged people not to 'figure-eight” the ties on a surgical mask in an attempt to make it fit: 'It creates tunnels at the cheek where viral particles will flow freely in and out”.

The Government started advising mask use in the midst of a global shortage of medical masks. Something is better than nothing, Kiwis were told – use a scarf, bandana or t-shirt, if you must.

'Early in the pandemic ... we were just trying to get people to cover up,” Rindelaub says.

Surgical masks are second-best to respirators, but they need to fit properly. Photo: Mika Baumeister/Unsplash

'But now that things have shifted, we know exactly how this virus transmits through aerosols, we have a better stock of these more high quality facemask.

'So it's time to make that transition, especially with Omicron right around the corner.”

'If everyone in New Zealand wore respirator-type masks all the time, the pandemic would stop immediately because there would be no more transmission,” epidemiologist Professor Michael Baker said.

Wearing respirator masks 24/7 isn't a practical way to live, so it's a 'balancing act” working out what situations need the highest level of precaution, Baker said.

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If a venue is indoors, crowded, with poor ventilation, a high-quality mask is a must.

New Zealand's slow adoption of mask use is partly down to our low case numbers, Baker said. While people in other countries have faced the near-certainty of encountering Covid-19 with every trip out the house, Kiwis hadn't. But Omicron looks set to change things.

Omicron is likely to cause an 'intense pandemic wave” when it arrives, Baker says. 'Suddenly taking all the precautions you can will seem absolutely essential.”

Omicron is better at breaking through vaccination protection, so even if you're vaccinated you still need good mask use, Telfar Barnard says.

Emergency Departments are preparing to see an onslaught of Omicron cases, once the Covid-19 variant starts spreading in the community.

Having a high-quality mask is important at an individual level – to protect you and those around you from the virus – and at a national level, to ‘flatten the curve' and stop the healthcare system from being overwhelmed, Baker said.

He wants to see a national mask strategy that would outline exactly when and where masks need to be used, with a focus on equity so everyone can access respirator masks that may otherwise be out of reach for low-income families.

The Ministry of Health has been approached for comment.

Dr Lucy Telfar Barnard's tips for mask use:

• Your mask needs to be an excellent filter.
• It needs to fit you really well.
• If you're sharing air (ie indoors or in busy/crowded outdoor areas) outside your bubble, you need to be wearing your mask, and you need to keep it well-fitted over your nose and mouth consistently.
• If you find yourself pulling the mask away from your face to talk clearly, or below your nose to prevent glasses, you either need a better mask, or better mask habits.
• If your mask has gaps round the edges (down the sides of your nose, in the sides at the cheeks, and under the chin are common gap points), you need a better mask, or you need to find a way to make it fit better.

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