Anne Wyllie. Image: Supplied / Tina Tiller
Anne Wyllie. Image: Supplied / Tina Tiller

Covid-19October 19, 2021

The golden drool: What makes saliva testing special in the fight against Covid-19

Anne Wyllie. Image: Supplied / Tina Tiller
Anne Wyllie. Image: Supplied / Tina Tiller

New Zealand has begun to introduce saliva testing, but it’s been slow in coming. Dr Anne Wyllie, a research scientist at Yale who led development of the SalivaDirect test, the protocol for which is openly shared and available to all at no cost, explains the value of such an approach in testing in workplaces, schools and elsewhere.

Racing daily against the potential of additional variants, vaccination programmes are gaining critical ground toward the goal of widespread community immunity against severe Covid-19 disease. Yet we must accept that even vaccinated individuals can become infected, mostly with milder symptoms, and transmit virus to the most vulnerable among us – particularly young children and the immunocompromised. So, as children are sent back to their classrooms and workplaces are repopulated, testing must become a new public health habit. 

New Zealanders need equitable access to affordable, reliable and effective Covid-19 testing readily located in their local communities. Having worked almost non-stop throughout the pandemic, developing Covid-19 tests, understanding test results and developing SARS-CoV-2 testing programmes for schools and workplaces, I know that our public health leaders must utilise all viable diagnostic methodologies – be it nasal or saliva-based PCR tests or rapid antigen tests — to help keep communities open. 

As a test sample type, saliva, when processed with scientifically-proven methods, serves as a powerful public health tool for the detection of SARS-CoV-2, the virus which causes Covid-19. Saliva is incredibly easy to collect. Adults and kids alike merely drool into a tube rather than submit to uncomfortable swabbing and does not require high-level healthcare workers. This is particularly important as healthcare workers, busy on regular days, face superhuman pandemic work schedules. Freeing them from testing programmes makes them available for vaccination programmes or to return to the clinic. Testing around the world has demonstrated that saliva can be reliably self-collected. This supports at-home sample collection, meaning no wait to be testing while protecting our healthcare workers from risk of exposure or burn-out.

Saliva, when tested properly, is at least as good as nasal swabs for SARS-CoV-2 detection. As methods are refined, saliva is being found to detect the virus earlier than swabs and in robust side-by-side studies it detects additional cases for whom swabs produced false negative results. Identifying infected individuals even 24 hours before they become contagious allows clinicians to rapidly take measures to isolate them from others and more quickly stop chains of transmission, preventing the closures of schools and workplaces. Saliva-based school and university testing programmes all over the US have proven successful, finding cases early and allowing safe, on-campus learning. If these tests were not accurate, the virus would instead quickly spread, risking the well-being of many.

SARS-CoV-2 also seems to clear faster from saliva. It’s well-known that swabs can test PCR-positive for months after Covid infection, but this appears not the case with saliva. When studying SARS-CoV-2 over the course of infection, the virus seems to clear more rapidly from saliva. This is likely more representative of one’s actual infection, rather than old pieces of virus simply being cleared by the body later on. Preventing false-positive test results has obvious savings of New Zealand healthcare resources and keeps pandemic response measures focused on sick individuals. More importantly, it prevents people from being unnecessarily isolated, protecting their earnings or their education – as well as their mental health.

Key to successful testing programmes, is the test itself. While saliva-based tests vary, we designed one to decrease demands on laboratory resources by streamlining the workflow down to a few simple steps. Reducing demands allows for higher sample throughput, vital for maximising testing capacity which is rapidly exhausted during large outbreaks. Additionally, this means that labs can produce test results within a few hours and deliver same day results to patients and caregivers, especially if locally based. Testing programmes should avoid flying samples across the country requiring them to sit around for longer and risk transfer delays. Rather, samples should be delivered in just an hour or two drive. Faster results means tighter infection control and less virus transmission.

From a testing sustainability viewpoint, laboratories need not purchase expensive tubes, buffers or special equipment to produce reliable, effective results with saliva-based tests. Moreover, variety is essential. Tests which reliably run with combinations of the most commonly available regents, materials and PCR equipment put less strain on critical sectors of the medical supply chain and allow labs to easily scale operations up and down while avoiding large inventory investments.

Combined, these many attributes make saliva-based testing much less costly than other approaches. Thanks to continued innovation by our SalivaDirect team and other labs around the world, saliva testing can not only be offered reliably but at a low cost. High-volume labs report total costs for supplies as low as one US dollar per test. Schools, workplaces and nationwide testing programmes alike need sustainable, reliable low-cost solutions which encourage participation. 

Looking forward, saliva has the potential to transform clinical testing. Covid-19 tests will be expanded to include other respiratory infections like influenza and RSV. This will help save time and resources needed to save individuals with flu-like symptoms from unnecessary isolation through better identification of the cause of symptoms. Saliva also holds promise for the detection of cancers or the presence of environmental toxins. This will help us more easily identify health threats and correct for them sooner. 

Despite increasing vaccination rates, as New Zealand opens back up its schools, universities and workplaces, Covid-19 testing schemes are essential for keeping tabs on the virus: where it is, who it is affecting, how it is changing and its potential to do more harm. Saliva-based methods enable frequent, comfortable, and highly reliable SARS-CoV-2 testing that can be rapidly scaled, when needed. Saliva presents a sustainable option from its simple self-collection, reducing demands on healthcare workers, to alleviating supply chains pressure and maximizing laboratory efficiency.

Saliva testing can be conducted more affordably, permitting Covid-19 response funds to go further and communities to stay safer, for longer. Replicating proven saliva methods permits faster implementation, providing a much needed public health response throughout the country. The hard work of New Zealanders to keep Covid-19 at bay has bought the country precious time to get its pandemic response right. With numerous examples around the world of how to establish effective testing programmes to reopen communities – and keep them open – it should be now more than clear that saliva should be considered a key component in this. 

Dr Anne Wyllie is a research scientist at the Yale School of Pubilc Health and advocate for saliva as a superior sample for creating high quality low-cost testing. Her paper on the subject attracted support by the NBA that led to the development of technology that has enabled others to make possible frequent testing keeping kids in school. The SalivaDirect test has transformed into a public health initiative: the test protocol is openly shared and available to all at no cost.

Mad Chapman, Editor
The Spinoff has covered the news that matters in 2021, most recently the delta outbreak. Help us continue this coverage, and so much more, by supporting The Spinoff Members.Madeleine Chapman, EditorJoin Members

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