Evidence Check - Epidemiology and transmission

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

Archive SARS-CoV-2 variants

Added: 20 Jan 2021
Updated: 5 Feb 2021

What is the evidence of the new SARS-CoV-2 variants (20B/501Y.V1 and 20C/501Y.V2) in terms of their infectivity, virulence, and effectiveness of the current vaccines?
  • Viruses constantly change through mutation and over time new variants of a virus are expected to occur.
  • New SARS-CoV-2 variants have recently emerged, most notably in the United Kingdom (UK), known as 20B/501Y.V1, variant of concern (VOC) 202012/01, or B.1.1.7 lineage and in South Africa known as 20C/501Y.V2 or B.1.351 lineage.
  • Other variants have recently emerged in Nigeria and Japan.
  • According to the World Health Organization the vaccines that have been approved should provide protection against variants, as the vaccines elicit a broad immune response.
  • While public health measures such as physical distancing, limitations on large gatherings and masks should remain effective, control of a more transmissible variant will require more widespread adoption of these measures.

Surgical masks, eye protection and PPE guidance

Added: 27 Jan 2022
Updated: 27 Jan 2021

What is the evidence for surgical masks in the endemic phase in hospitals and for eyewear to protect against COVID-19?
  • No evidence was found for or against the use of surgical masks in hospitals specifically during the endemic phase of the pandemic.
  • There is some debate on how best to develop transmission-based precautions that are effective as changes to universal precautions are made in the wake of COVID-19.
  • While ocular transmission has been proposed as a transmission route for SARS-CoV-2, via the nasolacrimal duct into the respiratory tract, there is no evidence of definite ocular transmission of SARS-CoV-2.
  • There is limited evidence on the effectiveness of eye protection in preventing SARS-CoV-2 infections.

Archive Deployment and vaccination plan for COVID-19

Added: 9 Dec 2020

What is the current guidance on developing a vaccination plan for COVID-19?
  • The World Health Organization (WHO) has released an interim guidance on developing a national deployment and vaccination plan for COVID-19 vaccines. This evidence brief provides a summary of this document, with supplementary information specific to the Australian context.
  • As of 2 December 2020, on the National Centre for Immunisation Research and Surveillance website, there were 213 vaccine candidates including 45 vaccine candidates in human clinical trials and 11 vaccine candidates in phase III clinical trials.
  • It is anticipated that most SARS-CoV-2 vaccines will require at least two doses for optimal immunogenicity. Storage and distribution temperature will likely be +2°C to +8°C for most vaccines but may require an ultra-cold chain of -20°C to -80°C storage for certain products.
  • The COVID-19 vaccine products are likely to have varying vaccine characteristics and presentations and will require different administration techniques.
  • The Australian government has established vaccination policy and secured agreements for the supply of four promising COVID-19 vaccines, provided they prove to be safe and effective.
  • Early studies looking at hypothetical COVID-19 vaccine acceptance amongst Australians estimated that approximately 4.9% would refuse and 9.4% are indifferent about receiving a COVID-19 vaccine. Inadequate health literacy and lower education level were associated with vaccine reluctance.

Archive High-risk settings for transmission of COVID-19

Added: 18 Nov 2020

What is the evidence for transmission of COVID-19 in different settings, and which settings are high-risk?
  • A statement from the Australian Health Protection Principal Committee (AHPPC) describes several very high-risk environments including nightclubs, dance venues, and large unstructured outdoor events such as music festivals, food festivals, school guardians’ festivals, carnivals, community sporting events and other non-ticketed spectator events. These events are high risk due to factors such as but not limited to large numbers, close proximity and mixing between groups of people.
  • Healthcare and residential aged care settings are known to be high risk but are excluded from this review
  • A systematic review identified 22 types of settings, predominantly indoor settings that result in SARS-CoV-2 transmission clusters. Risk was classified based on the number of infections per cluster or the proportion of people in that setting who became infected. Most clusters involved fewer than 100 cases, with the exceptions being in large religious gatherings, food processing plants, schools, shopping, and large co-habiting settings (worker dormitories, prisons and ships). Other settings with examples of clusters between 50–100 cases in size were weddings, sporting events, bars, shops and workplaces.
  • A rapid review, prepared by The National Collaboration Centre for Methods and Tools looking at risk of COVID-19 transmission across different indoor settings in the community, reported that households and shared accommodations (e.g. cruise ships) thus far appear to be the most prevalent locations for infection clusters. In settings involving indoor physical activity (gyms and fitness classes), attack rates are highly variable and range from 7.3-26.3%. Transmission appeared to occur more commonly from fitness instructors to participants. Furthermore, modelling studies estimated risk level for different indoor scenarios found ventilation, reducing crowd size, wearing a mask and physical distancing may decrease transmission risk.
  • Most evidence were from single case reports. For many settings, there were insufficient data to determine whether the settings are categorically high risk. Studies were mostly descriptive, with some concluding that transmission was likely facilitated by close proximity. Indoor settings featured in the literature included: Establishments providing accommodation: homeless shelters, prisons, work dormitories, cruise ships Occupational settings: military, factories, offices, call centres and schools. Social/recreational settings: family and religious gatherings, shopping centres, choir, restaurants, fitness centres and aircrafts.

Archive Infection control recommendations in the emergency department according to local transmission risk

Added: 4 Nov 2020

What personal protective equipment (PPE) and other infection control measures are implemented in the emergency department (ED) during COVID-19
and do they differ according to levels of community transmission?
  • Studies of ED infection control measures in response to COVID-19 are predominantly descriptive in nature, and generally do not provide detail regarding levels of local disease prevalence. Risk assessment in the ED generally considers the risk an individual patient has of contracting COVID-19 based on their history and clinical picture, rather than adopting a population perspective, which considers local transmission rates. Frequently reported infection control or risk mitigation measures used in EDs include the following.
  • Recommendations for PPE use – PPE recommendations are mainly based on patient risk stratification or assessments of aerosol generating procedures. Studies describe the use of full PPE when interacting with patients with symptoms or high risk epidemiological history, when working in designated ‘fever clinics’ or triage, or when performing aerosol generating procedures.(1-6). One study from Europe found that 82% of EDs surveyed implemented surgical mask use for patients.(4)
  • Triage – dedicated triage stations either in tents or prefab houses located outside the main ED building, at the entrance or inside the ED in a separate area.(1, 5, 7-19)
  • Zoning or partitioning of the ED areas – division of triage, waiting and clinical areas in the ED into separated zones for placing patients based on their COVID-19 risk stratification.(2, 3, 8-13, 18, 20-25) Some recommend differential PPE and the use of protocols for healthcare providers working in different zones.(2, 7, 24)
  • Negative pressure rooms – use of fans in existing structures, or medical tents are described.(4, 8, 10, 11, 26)
  • Telemedicine – audio and video devices or call centres to provide assessment or consultation for patients either before they present to ED, or while being triaged or waiting or isolating in the ED rooms, especially for those not in immediate need for physical examination or resuscitation.(7, 8, 18, 19, 22, 27-30)
  • Healthcare worker cross-infection prevention – a range of interventions are described including: reducing the number of non-clinical employees in the ED
  • using telemedicine, separating dining, rest and office areas and partitioning spaces using transparent boards
  • using portable computers, using instant messaging for disseminating information
  • regular monitoring and logging of healthcare provider symptoms and enhanced cleaning of work areas and equipment.(3, 5, 12, 28, 31, 32)
  • Portable or mobile diagnostic testing equipment – use of portable X-ray in different zones of ED or a truck equipped with diagnostic devices.(11, 33)

Archive Second spike in COVID-19 cases

Added: 28 Oct 2020

What are the contributing factors of a second spike in COVID-19 cases?
  • Epidemiology reports in Australia highlight COVID-19 notifications by week of diagnosis, with timing of key public health measures. Prior to the second wave in Victoria, there was a start of easing of restrictions in select states and territories on 27 April.
  • A global overview of second waves found three distinct time periods in the data. Cases rose to mid-April, plateaued till mid-May then rose again. Almost all the slopes in these three time periods were statistically significant. Deaths followed a similar pattern.
  • Common factors that were linked to a second spike in countries included imported cases, negligent hotel quarantine program, easing lockdown measures, relaxation of social distancing practices, especially among young people, and mass gatherings or events.
  • Singapore and Japan saw a second spike in March after initially curtailing the first spike in COVID-19 cases. This was mainly driven by imported cases from European and North American countries and community transmission among foreign migrant workers living in dormitories in Singapore. In several jurisdictions including Hong Kong, China, Nepal and Vietnam, imported cases prompted new waves of outbreak.
  • Japan experienced a further surge in cases in August, which was attributed to the lack of scrutiny and transparency from the government, inadequate testing, lack of efficient digital reporting system and a domestic tourism campaign.
  • In Malaysia, the second surge in cases was associated with clusters originating from religious and other gatherings. In Vietnam, almost half of new cases during the second wave were found in the hospital setting. Easing of social distancing and leisure activities of young people were associated with second waves in South Korea, Hong Kong and Iran.
  • Two major provinces in South Korea experienced a resurgence in cases after easing lockdown measures, with the majority of new clusters associated with nightclubs, religious facilities, sports clubs, and indoor promotional events. The second wave had a higher proportion of asymptomatic cases than the first wave, especially among the 20-39 age group. This could be due to extensive contact tracing and testing among this age group in investigating clusters originating from leisure-venues and workplaces. This age group may otherwise delay testing or have lower rates of screening.
  • European countries that had seen a sustained decline in cases after an initial peak started to experience a spike, which was attributed to easing of lockdown measures, relaxation of social distancing practices, increased number of testing, younger people continuing to engage in social gatherings, two mass events, and delays in implementing locally coordinated, culturally appropriate and accessible public health interventions.
  • An analysis of the second wave of COVID-19 in 26 countries found that the second wave of infections was mainly among younger age groups and the rate of spread increased with the rise of temperature. A second analysis article found that the second wave had a lower case fatality rate than the first wave.

Archive COVID-19 infection and transmission in domestic animals

Added: 15 Sep 2020
Updated: 16 Sep 2020

Can domestic animals become infected with COVID-19, and is there evidence of transmission of COVID-19?
  • There have been isolated incidents of domestic animals testing positive for the COVID-19 virus. (1-7) Generally, in these cases, the pet owners have been COVID-19 positive.
  • The infected domestic animals reported in the literature are mainly dogs and cats, and studies reported either natural (1, 2) or experimental infection with the SARS-CoV-2.(6, 8, 9)
  • Infected pets may show clinical symptoms (2, 3), or they may remain asymptomatic.(4, 10, 11) Most of the pets that were infected with COVID-19 had mild symptoms and fully recovered.

Archive Surgical masks and oxygen therapy

Added: 19 Aug 2020

What is the evidence for wearing a surgical mask at the same time as an oxygen mask?
  • In vitro and clinical studies have demonstrated that placing a surgical mask on patients significantly reduces dispersion distance and levels of virus-infected bio-aerosol 20cm away from patients while coughing.
  • To mitigate the risk of spread of disease, a nasal cannula can be placed and covered with a surgical mask to limit the potential for environmental contamination.
  • Evidence on the percentage of supplemental oxygen that is delivered to the patient when wearing both a surgical mask and oxygen mask in the context of COVID-19 is lacking. A short report tested breathing air wearing a surgical mask on the face, second, breathing 6 l.min−1 oxygen via a Hudson mask placed over the top of a surgical mask and third, breathing 6 l.min−1 oxygen via a Hudson mask placed underneath a surgical mask, where the FIO2 measured was 0.20, 0.50 and 0.54, respectively.
  • Evidence on whether an oxygen mask can be worn over the top of a surgical mask, or underneath it includes: o A joint international consensus document recommends keeping a simple surgical face mask on patient, over nasal prongs and under any type of oxygen face mask. A short report calls for a surgical mask to be placed over the patient’s nose and mouth immediately following extubation, and for a Hudson mask to be placed on top due to the negligible difference in FIO2 when the Hudson mask is placed over a surgical mask. Chinese consensus guidelines also describe that the surgical or N95 mask is applied under the oxygen mask. While some consensus guidelines recommend placement of a surgical mask over patients being treated with high flow therapies.

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.

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