The widespread use of face masks is vital to keeping the coronavirus R number below 1.0 and preventing further waves, new research from the University of Greenwich suggests.

The new modelling study indicates that lockdowns alone will not stop the resurgence of Covid-19, but 100% mask adoption combined with on/off lockdowns will prevent any further disease resurgence for the 18 months required for a possible vaccine.

Researchers say even homemade masks with limited effectiveness can dramatically reduce transmission rates if worn by enough people, regardless of whether they show symptoms.

The project comes from the universities of Cambridge and Greenwich, and the results support “the immediate and universal adoption of face masks by the public.”

Lead author, Dr Richard Stutt, part of a team that usually models the spread of crop diseases at Cambridge's department of plant sciences, said: “If widespread face mask use by the public is combined with physical distancing and some lockdown, it may offer an acceptable way of managing the pandemic and re-opening economic activity long before there is a working vaccine."

Covid-19 is transmitted through airborne droplets that get exhaled by infectious people, particularly when talking, coughing or sneezing.

For the latest study, researchers worked to link the dynamics of spread between individuals with population-level models, to look at different scenarios of face mask adoption combined with periods of lockdown.

The modelling included stages of infection and transmission via surfaces as well as air. Researchers also considered negative aspects of mask use, such as increased face touching.

The reproduction, or R number is the number of people an infected individual passes the virus onto, needs to stay below 1.0 for the pandemic to slow.

Experts say the R number in the UK is currently 0.7-0.9.

Professor John Colvin of the University of Greenwich and co-author for the study said: "There is a common perception that wearing a face mask means you consider others a danger.

"In fact, by wearing a mask you are primarily protecting others from yourself.

"Cultural and even political issues may stop people wearing face masks, so the message needs to be clear: 'my mask protects you, your mask protects me'.

"In the UK, the approach to face masks should go further than just public transport.

"The most effective way to restart daily life is to encourage everyone to wear some kind of mask whenever they are in public."

The study, published in the Proceedings of the Royal Society A, found that if people wear masks when in public, it is twice as effective at reducing R than if masks are only worn after symptoms appear.

In all modelling scenarios, researchers found routine face mask use by 50% or more of the population reduced Covid-19 spread to an R less than 1.0.

This flattened future disease waves and allowed less-stringent lockdowns.

According to the study, 100% mask adoption combined with on/off lockdowns prevented any further disease resurgence for the 18 months required for a possible vaccine.

The models suggest that - while the sooner the better - a policy of total face mask adoption can still prevent a second wave even if it is not instigated until 120 days after an epidemic begins.

The researchers say homemade masks primarily reduce disease spread by catching the wearer's own virus particles, whereas inhaled air is often sucked in around the exposed sides of the mask.