Evidence Check - Epidemiology and transmission

Community transmission and hospital infection, stages of pandemic, immunity, vaccination.

Omicron (B.1.1.529) variant

Added: 10 Dec 2021
Updated: 24 Dec 2021

What is the evidence for the variant of concern Omicron (B.1.1.529) in terms of transmissibility, disease severity, COVID-19 treatments and vaccines?
  • Omicron (B.1.1.529) was designated a variant of concern by the World Health Organization on 26 November 2021.
  • It was first reported to WHO from South Africa on 24 November 2021.
  • It has 50 mutations, including 26-32 mutations on its spike protein.

COVID-19 vaccines in Australia

Added: 19 Aug 2021
Updated: 17 Dec 2021

What is the evidence on COVID-19 vaccines in Australia?
  • Internationally, 28 vaccines are approved and 8.55 billion doses have been administered.
  • All vaccines that are approved for use have strong safety profiles and benefit to risk ratios.
  • In Australia, three vaccines have been approved for use. To 12 December 2021, approximately 25.3 million doses of Comirnaty (Pfizer), 13.6 million doses of Vaxzevria (AstraZeneca) and 1.3 million doses of Spikevax (Moderna) vaccines have been administered.

Face masks and COVID-19 transmission in the community

Added: 29 Oct 2021
Updated: 16 Dec 2021

What is the evidence for the effectiveness of face masks in community settings for reducing influenza-like illnesses, including COVID-19?
  • Most systematic reviews report benefits in terms of reduction in incidence, hospitalisation and/or mortality.
  • The efficacy of protection against respiratory viral infections may vary according to the type of mask used.
  • Face masks are often recommended alongside other protective measures including hand hygiene and physical distancing.

Paediatric respiratory infections

Added: 6 Dec 2021

What is the evidence for paediatric respiratory infections after lockdown and school reopening during COVID-19?
  • Countries in both southern and northern hemispheres reported no immediate impact on the incidence of respiratory pathogens following reopening of schools and day care centres. However, some countries such as the U and China reported eran increase in intseasonal RSV activity.
  • There is a concern that due to the reduced circulation of RSV during the winter months of 2020/21, older infants and toddlers might now be at increased risk of severe RSV-associated illness since they may not have had typical levels of exposure to RSV during the past 15 months.
  • In several jurisdictions, the routine use of influenza vaccines and antiviral medications in the prevention and treatment of respiratory infections in children are recommended.

Deep cleans

Added: 19 Apr 2021
Updated: 6 Dec 2021

What is the evidence for fomite transmission and deep cleaning of COVID-19?
  • In February 2020, the World Health Organisation (WHO) noted fomites as a potential route ofCOVID-19 transmission.1 However, in July 2020, an update noted that despite consistent evidence of SARS-CoV-2 RNA on certain surfaces, there is no direct evidence of fomitetransmission.
  • Despite the low risk of fomite transmission, there continues to be significant investment in deep-cleaning and disinfection to reduce potential surface contamination . A Nature perspective in January 2021 questioned the value of this.

Hospitalisation and ICU admission relative risk

Added: 4 Nov 2021

What is the evidence for the relative risk of hospitalisation and ICU admission for vaccinated versus unvaccinated people?
  • The effectiveness of vaccines can be assessed by comparing the risk of hospitalisation or ICU admission among vaccinated versus unvaccinated people.
  • Data from NSW has shown that the majority of COVID-19 patients in intensive care units are unvaccinated or only partially vaccinated.
  • In patients 16 years and older, there was a 24-fold higher risk of hospitalisation and a 46-fold higher risk of ICU admission in unvaccinated people compared to vaccinated people. The difference increases in the 40-59 years age group, with a 47-fold higher risk of hospitalisation and a 70-fold higher risk of ICU admission.

De-isolation and risk of transmission

Added: 29 Oct 2021

What is the evidence for de-isolation and the risk of COVID-19 transmission?
  • The likelihood of shedding infectious virus beyond 10 days following symptom onset is very low in COVID-19 patients with mild to moderate disease and remains low in severely ill COVID-19 patients.
  • Generally, 10 days passed since COVID-19 symptoms or date of first positive test is the timeframe from discontinuation of transmission-based precautions, including isolation. In Australia, the Communicable Diseases Network Australia uses 14 days passed as the criteria.
  • Extended isolation and precautions for up to 20 days after symptom onset may be warranted in some cases.

COVID-19 vaccine booster shots

Added: 12 Oct 2021

Evidence check on COVID-19 vaccine booster shots
  • While there is evidence of a reduction, or waning, of serum antibodies to SARS-CoV-2 post-vaccination, vaccines continue to provide effective protection against symptomatic and severe disease and death
  • The effect of waning immunity is still emerging internationally. Some jurisdictions such as Israel, have seen high rates of hospitalisation concurrent with waning immunity, while others such as the United Kingdom (UK), have seen a decline in hospitalisations and deaths despite decreasing antibody levels.
  • This has raised questions about the need for booster doses of vaccine.

Daily Evidence Digest

Rapid evidence checks are based on a simplified review method and may not be entirely exhaustive, but aim to provide a balanced assessment of what is already known about a specific problem or issue. This brief has not been peer-reviewed and should not be a substitute for individual clinical judgement, nor is it an endorsed position of NSW Health.

Back to top