COVID-19 Evidence Updates

The question of whether it is safe and appropriate for children to continue attending schools has, and continues to, cause debate.

This Evidence Update addresses the way COVID-19 seemingly affects children differently to adults, the modelling of how school closures would affect community transmission and parallel considerations such as the impact of school closures on caring duties, particularly for health care workers and elderly relatives.

There is a concern that people whose immune systems are weaker because of age, medical conditions or treatment such as chemotherapy could be at greater risk of contracting COVID-19 and suffering more severe symptoms.

This Evidence Update focusses on the infection risk to people undergoing immunosuppressant cancer treatments. It investigates the effect of the treatment itself as well as parallel factors such as the need to regularly leave isolation to visit hospitals and clinics for treatment and check-ups.

“Viral load” and “viral inoculum” refer to the level of a virus within an infected person’s body and the amount of virus that person was initially exposed to. Using the limited COVID-19 evidence available, combined with evidence from similar viruses including Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS) and the flu, Professor Miller’s team extrapolated that exposure to higher amounts of the virus that causes COVID-19 is likely to cause a higher viral load which in turn increases the severity of the infection.

There is anecdotal evidence that loss of smell and/or taste is an early symptom of COVID-9 infection. It’s been suggested that if this happens before known symptoms including fever and a dry cough, it could be used to promote earlier testing and diagnosis, therefore limiting transmission of the virus.

Professor Miller and her team used the limited published work on this topic, clinical testimonies and estimates of the prevalence of loss of taste and smell among the general population to assess whether these symptoms are a reliable indicator of COVID-19 infection.

Much of the need to control the spread of COVID-19 and “flatten the curve” is to prevent hospitals, and intensive care units in particular, from being inundated with more patients than they have the resources to care for, as we have seen in other countries.

To help prepare for the possible impact on our health system, Professor Miller’s team was tasked with identifying what potentially makes people who contract COVID-19 more likely to need intensive care treatment.

Questions have been raised about possible implications COVID-19 could have for pregnant women and their babies during pregnancy, during birth and postnatally.

Professor Miller and her team collected evidence specific to COVID-19 as well as evidence from similar infections such as SARS and MERS.

Aged care facilities present high risk of transmission in the event of a COVID-19 outbreak while the residents of these facilities are typically more vulnerable to severe impacts from the virus.

While there have been no studies addressing these issues, this Evidence Update collects the best practice guidelines available to prevent outbreak and spread. The strategies can also be applied to other institutional settings such as prisons and psychiatric facilities.

Fortunately, there have as yet been no cases of COVID-19 in remote Indigenous communities in South Australia however these regions present unique challenges for managing an outbreak if it were to happen.

Professor Miller, Professor Alex Brown and their team address those challenges in this Evidence Update, including balancing the need for a rapid response and with observance of quarantine protocols designed to prevent further transmission of the virus into these areas.

Certain demographics such as the elderly, people with weakened immune systems and those with existing medical conditions have been found to be more at risk from COVID-19 infection.

This evidence update addresses whether smokers are more susceptible to contracting COVID-19 and whether, once infected, their symptoms are worse. The team also specifically looks at issues around shisha smoking and vaping.

South Australia’s success in suppressing COVID-19 transmission understandably has people looking ahead to when and how life can return to “normal”.

The Evidence Synthesis team investigates the “end to an epidemic” in this update – specifically using the incubation period for the virus that causes COVID-19 to advise timelines around when the virus can be considered controlled.

Screening people for fever – a symptom of COVID-19 – has been widely discussed as a measure to help limit the spread of the virus, especially at public sites where relatively large numbers of people gather.

This evidence update weighs the costs of broad screening against the potential benefits, taking into account issues such as the predictive value of fever as a COVID-19 symptom, the effectiveness of non-contact temperature testing technology and the resources needed to conduct and respond to screening.

Victoria’s largest COVID-19 cluster centred on a meat processing plant and abattoirs have been associated with scores of cases internationally, particularly in the US and Ireland.

Professor Miller and the team investigate possible explanations in this evidence update, including low temperatures on meat processing floors, close proximity of workers, multiple handling of materials and the biological nature of meat.

With State and Federal Governments gradually easing COVID-19 restrictions, thoughts are turning to how we can safely resume “normal” activities such as domestic air travel.

This evidence update addresses the likelihood of COVID-19 being transmitted during domestic flights and potential measures that could reduce that likelihood.

People who contract COVID-19 develop symptoms at different stages post-infection, while some don’t show symptoms at all.

The chances that people with COVID-19 can infect others despite showing few or no obvious symptoms is the subject of this evidence update.

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Asymptomatic and pre-symptomatic cases and transmission of SARS-COV-2 (PDF 661KB)

South Australia is one of several jurisdictions fortunate to have suppressed COVID-19 to the point of virtual elimination. But with the disease still prevalent in other areas, the possibility of ‘importing’ it is ever-present.

In this update, the evidence synthesis team assesses various mechanisms that are being employed around the world to control viral spread. They also investigate the ‘outbreak threshold’ at which point an outbreak could become uncontrolled or uncontrollable.

Many jurisdictions across Australia and the world have employed lockdowns of various degrees as a primary tool against the spread of COVID-19. The theory is that restricting population movement will reduce contact between people and so limit disease transmission. But does it work? What degree of ‘lockdown’ is necessary? And at what stage does it need to be enforced?

Professor Caroline Miller and her team investigate these questions and more in this Evidence Update.

The responses to COVID-19 have been many and varied between countries, and even between jurisdictions within countries, but there are some common factors between those who have been relatively successful.

This evidence update investigated an array of response factors including timing, border controls, lockdowns, testing, contract tracing, health system capacity and communication.

When a person is confirmed to have contracted COVID-19, contact tracing can determine where they got the infection from and who they might have already spread it to. It’s a crucial tool in slowing the spread of the virus but there are several factors that influence its effectiveness.

This evidence update examines the key indicators which make contact tracing effective, such as how quickly contacts must be traced, and how it is impacted by complementary strategies including technology, policy and population compliance. The update also looks at international examples of what has and hasn’t worked in different jurisdictions.

COVID-19 safety restrictions around hospitality, entertainment and other sizable public gatherings have been among the most contentious since the onset of the virus.

This evidence update addresses the risks posed by these activities, factors that potentially amplify these risks and strategies that have been proposed to allow some of these activities to resume safely.

In the 10 months since the original Evidence Update there have been a number of reviews of the evidence as well as new primary case studies, observational environmental detection studies and expert summaries.

This update takes this additional information into account while assessing the likelihood that COVID-19 can be transmitted via contact with inanimate objects.

People who contract COVID-19 can have severe symptoms, no symptoms at all or somewhere in between.

This evidence update investigates whether the severity of symptoms affects how infectious a person is and whether vaccination will impact the likelihood of spreading the disease.

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Symptoms, Vaccination and Infectiousness (PDF 2.7MB)

COVID-19 vaccines are being administered around the world and in Australia, with more than 300 million people already being immunised globally.

This Evidence Update addresses the real-world impact of the vaccination program and its implications for future easing social, business and travel restrictions.

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Real world impact of vaccines and implications for COVID-19 control (PDF 550KB)

A variety of considerations must be taken into account before allowing the return of international students to South Australia’s schools and universities. These include the status of COVID-19 control in the country of origin, whether the individuals have been vaccinated and the quarantine controls arrivals would be subject to.

This Evidence Update addresses these considerations and more, looking specifically at China, Hong Kong, Singapore and Vietnam.

Many jurisdictions around Australia and the world have made wearing masks in public settings mandatory as COVID-19 case numbers rise.

The Evidence Synthesis team has analysed available evidence relating to the level of protection masks provide to wearers, their effectiveness in preventing spread from infected individuals and what other COVID-19 controls should be used in conjunction with mask wearing to increase effectiveness.

People who contract COVID-19 will be required to isolate for different periods of time depending on where in the world they are living.

In this evidence review, the team examines what the science says about the decline of infectiousness after people become symptomatic.

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Infectiousness and isolation of COVID-19 positive cases (PDF 376KB)

This evidence review investigates the impact of COVID-19 variants on the need for further vaccinations, and the optimal time between doses.

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Third dose vaccine scheduling for COVID-19 (PDF 259KB)