Estimating around 19% of the population to remain unprotected after vaccine roll out, expert epidemiologist outlines how rapid antigen tests could augment gold standard PCR testing

In a recent Abbott sponsored webinar, hosted by the Australian Society for Antimicrobials, Abbott’s Global Scientific Affairs Director, Rapid Diagnostics Norman Moore, presented alongside Professor Mary-Louise McLaws, an epidemiologist at the University of New South Wales, on the role rapid antigen tests could play in public health responses to COVID-19.

Professor McLaws has consistently advocated for the use of rapid antigen tests in certain settings to augment gold standard PCR testing. This includes screening essential workforces such as hotel quarantine facilities in real-time at the end of every shift.

"I believe rapid antigen tests should be part of an augmentation of PCR and could be used to test every other day," she said.

"The more frequently you test in the same community, the more effective these tests become.

"The respiratory viral load is very high right at the beginning in the pre-symptomatic phase. It’s the high-risk group that you want to target with your rapid antigen test when they are in this phase.

"If you test a worker at the end of a shift and they receive their results in 15-20 minutes, you can immediately prevent them from going out into the community if they are infectious."

Now advisor to the World Health Organisation (WHO), McLaws is calling for their use in support of Australia’s vaccine roll out for screen testing in a number of settings as we begin to safely open up including:

• Borders
• Public gatherings
• Fly-in fly-out workers
• Remote communities

This, Professor McLaws argues, is because even after vaccines have been offered to the entire eligible population, a proportion of the public will not be protected.

Therefore, public screening with rapid antigen tests should be used to keep on top of potential outbreaks as they emerge.

"Post-vaccination there will still be many of us who won't be protected, I estimate about 19%, and there will be a proportion of people who can't or choose not to be vaccinated who will also be unprotected. So there will still be a need for rapid antigen tests for screening particularly for opening up safely," she added.

"People should be screened when they get onto a plane and when they get off a plane, because of the proportion on that flight who aren’t protected. All return travellers vaccinated or not must be tested on arrival, not wait until Day-2 of return, to reduce the transportation between facilities and reduce the risk a breach in quarantine."

Rapid antigen tests have a proven particularly effective in high prevalence settings such Europe, UK and the United States.

Abbott's Norman Moore noted the issue of laboratories becoming overwhelmed during surges in the US, leading to slow turnaround times and infectious people circulating in the community infecting others.

"On average you’re actually only infectious for about eight or nine days, so if you were waiting up to a week for a result, you were passed the point of being infectious," he said.

Another positive attribute of rapid antigen tests Norman Moore highlighted, is their sensitivity early in infection. A PCR test can show up positive months after someone has contracted the virus and long after they are infectious, he argues.

"When we started developing COVID-19 tests, we decided we wanted ultimate sensitivity, but surprisingly we're actually seeing with some people that the RNA would last for months," he added.

"This is one of the big issues we've been seeing; you can be producing the virus longer than is actually infectious."

An issue keeping the global medical community awake at night is the emergence of new variants such as those seen in the UK, Brazil, South Africa and India.

Although sufficient evidence is lacking to draw solid conclusions, early indications suggest some are more infectious strains.1

But Norman Moore says Abbott’s tests remain effective against the variants.

The ID NOW COVID-19 test detects the RNA dependent RNA polymerase (RdRp) gene and is therefore unaffected by any mutations outside of that region/gene. The Panbio COVID-19 Ag detects the nucleocapsid (N) protein and Abbott scientists have assessed these amino acid changes to the protein in silico and determined that there would be no impact on performance from the reported mutations.

Through Abbott’s Global Virus Surveillance Program, Abbott will continue to monitor the global situation on the SARS-CoV-2 variants, allowing the Abbott teams to stay one step ahead.

"The first thing that happens in the virus hunting lab in Chicago is the sequences are published, then we make sure the sequences don’t have an issue in the areas we target. Then we grow the virus and test it across all those platforms."

References

1 https://www.cdc.gov/coronavirus/2019-ncov/transmission/variant.html