Evidence check
A rapid review outlining the available evidence on a discrete topic or question. Evidence includes grey and peer review literature. View all Evidence Checks by date of publication.
Archive Delta variant
Added: 19 Aug 2021
Evidence in brief on the Delta variant
- The Delta variant has been estimated to be more than twice as transmissible as the originalstrain of SAR-CoV-2. First recognised in India, it has now spread to over 100 countries.
- The current NSW outbreak is due to the Delta variant.
- The risk of hospitalisation from COVID-19 is almost doubled for patients infected with Delta (Sgene positive cases), compared with people infected with the Alpha variant. Both the Oxford–AstraZeneca and Pfizer–BioNTech COVID-19 vaccines were effective in reducing the risk ofSARS-CoV-2 infection and COVID-19 hospitalisation in people with Delta.
Archive COVID-19 and maternity and newborn communities of practice
Added: 2 Jul 2021
What is the best practice management of a COVID-19 positive neonate?
What is the current evidence for vaccinating breastfeeding and pregnant women and women who are on oral contraceptive pill?
What are the current recommendations for infection control measures for group sessions in an indoor setting?
What is the current evidence for vaccinating breastfeeding and pregnant women and women who are on oral contraceptive pill?
What are the current recommendations for infection control measures for group sessions in an indoor setting?
- There is no clear evidence of vertical transmission of SARS-CoV-2. In COVID-19 positive neonates born to infected individuals, it is challenging to determine if the transmission occurred in utero, intrapartum or postpartum due to lack of standardised international definition and classification system for timing, diagnostic testing limitations, such as lack of timely collection of appropriate specimens and method specificity and sensitivity.
- A population-based cohort study from the United Kingdom estimated the neonatal incidence of SARS-CoV-2 infection to be 5-6 (95% confidence interval 4·3-7·1) per 10,000 live births. In an overview of systematic reviews of outcomes of COVID-19 positive mothers, the neonatal polymerase chain reaction positivity rates range between 1.6% and 10%. There were reports of neonates with serum antibody positivity yet negative polymerase chain reaction (PCR) positivity. There is no clear evidence of SARS-CoV-2 transmission to neonates via breastmilk.
- Around 20% of neonates with SARS-CoV-2 infection are asymptomatic and further 40%-50% have mild symptoms. Reported symptoms include rhinorrhoea, cough, lethargy, vomiting, diarrhoea, apnea, fever, tachycardia, tachypnea, leucocytosis, thrombocytopenia, hypoxemia, hypotension, raised C-reactive protein, elevated lactate and radiographic findings of ground-glass opacities. Early onset of neonatal COVID-19 infection (between two and seven days after birth) is likely, however, the majority of symptomatic infections are late-onset (after 7 days of birth).
Archive Facial hair, masks and COVID-19 transmission
Added: 25 Jun 2021
Optimal use of respirator face masks such as N95 or filtering facepiece masks depends on a tight seal with the wearer's skin.
- Tight-fitting respirator face masks such as N95 or filtering facepiece masks are considered the reference standard respiratory protective equipment for healthcare workers working in aerosol-generating procedures. Optimal use of these depends on a tight seal with the wearer's skin.
- The purpose of fit testing is to ensure that the selected make, model and size of a respirator issued to a wearer forms an adequate seal around the wearer’s face providing protection. The Critical Intelligence Unit has published an evidence check on respirator fit testing.
- The Clinical Excellence Commission recommends that healthcare workers must not have any facial hair present when commencing fit testing and when using a respirator. International organisations consistently describe facial hair as a contraindication to the workplace use of tight-fitting respirator masks.
- Many organisations, for example the US Centers for Disease Control and Prevention, provide graphics depicting facial hairstyles and filtering facepiece respirators.
- A requirement to be clean shaven to facilitate the effective wearing of respiratory protective equipment may indirectly discriminate against certain groups.
- The COVID-19 pandemic has seen a shift away from beards towards clean shaves in response to personal protective equipment guidance.
Archive Respirator fit testing
Added: 29 Oct 2020
Updated: 25 Jun 2021
What is the effectiveness of fit testing (both qualitative and quantitative methods) and fit checking for testing the protection of a respirator and what are the factors influencing the outcomes of fit testing?
What are the differences in outcomes between the qualitative and quantitative fit testing methods?
What are the differences in outcomes between the qualitative and quantitative fit testing methods?
- The purpose of fit testing is to ensure that the selected make, model and size of a respirator issued to a wearer forms an adequate seal around the wearer’s face and provides the intended level of protection.(1) The Australian New Zealand Standard AS/NZS1715:2009 Selection, Use and Maintenance of Respiratory Protective Equipment states that fit testing can be performed using qualitative or quantitative methods. • Qualitative fit testing is a pass/fail test method that uses the wearer’s sense of taste or smell to detect leakage into the respirator facepiece. This type of fit testing is usually used for half-mask respirators. • Quantitative fit testing measures the amount of leakage into the facepiece using a generated aerosol, ambient aerosol or controlled negative pressure. This type of fit testing connects a respirator to a machine using a probe attached to the respirator.
- Fit checking (user-seal check) describes the process that health workers perform each time a respirator is donned to check that a good facial seal is achieved, i.e. the respirator is sealed over the bridge of the nose and mouth and there are no gaps between the respirator and the face.
Archive COVID-19 vaccine and elective surgery
Added: 20 May 2021
What is the evidence on COVID-19 vaccination before elective surgery, including any recommendations regarding timing of vaccination?
- Expert consensus from international professional societies generally recommend vaccinating patients against SARS-CoV-2 before elective surgery, as this may reduce the risk of COVID-19 complications and transmission of the virus during procedures.
- Recommendations on the timing for preoperative COVID-19 vaccination is variable, ranging from a few days to weeks due to the unknown vaccine immunogenicity.
- COVIDSurg, a modelling study based on data from almost 60,000 patients internationally, found that fewer people need to be vaccinated to prevent one death in surgical patients compared with the general population.
- COVIDSurg estimated that globally, prioritising all surgical patients for preoperative vaccination ahead of the general population is projected to prevent an additional 58,687 COVID-19-related deaths in one year.
- The timing for surgery, and potential for vaccine prioritisation, would need to take into account the context of the surgery and disease prevalence. For example, in some settings it may not be appropriate to prioritise surgical patients over vulnerable groups such as the elderly, and advice may vary for different surgeries.
- The Royal College of Surgeons of England recommends that emergency surgery take place irrespective of COVID-19 immunisation status.
Archive Vaccine hesitancy
Added: 13 May 2021
Evidence in brief on vaccine hesitancy
- Vaccine hesitancy lies somewhere between complete acceptance and refusal of all vaccines. Factors that contribute to vaccine hesitancy include confidence in the vaccine and/or provider, complacency and convenience.
Archive Cerebral venous sinus thrombosis after AstraZeneca vaccination
Added: 30 Apr 2021
Evidence in brief on CVST after AstraZeneca vaccination
- In recent weeks there have been concerns about blood clots occurring in patients after they were given the AstraZeneca vaccine.(1) Most reports involved women under 55 years.(2)
- These reports included 18 cases of cerebral venous sinus thrombosis (as of 17 March 2021).(3)
- Cerebral venous sinus thrombosis (CVST) refers to the presence of a blood clot in the dural venous sinuses, which drain blood from the brain. Symptoms may include: headache, abnormal vision, any of the symptoms of stroke, such as weakness of the face and limbs on one side of the body and seizures.(4)
- CVST is rare, occurring at a rate of between two and five people per million.(4)
- Cerebral venous sinus thrombosis (CVST) can be a complication of COVID-19. A case series of 14 patients noted most received anticoagulation (91.7%) and a mortality rate of 45.5%.(5, 6)
- The main treatment for CVST is anticoagulation. There are, however, concerns that heparin is contraindicated in the rare cases of CVST following vaccination (particularly with AstraZeneca vaccine).(7)
- It has been proposed in Germany and Norway that post-AstraZeneca vaccination CVST may be similar to a syndrome known as heparin-induced thrombocytopaenia or HIT (sometimes referred to as heparin-induced thrombotic thrombocytopaenia or HITT.(8, 9)
- HIT is characterised by an anti-platelet factor 4 antibody response – leading to platelet consumption and thrombosis.(10)
- Notably, HIT features high thrombotic risk despite only mild to moderate thrombocytopenia. For example, the median platelet count nadir in HIT is approximately 55 to 70 × 109 /L, with a high proportion of patients (~30-50%) with platelet count nadirs >100 × 109 /L or even >150 × 109 /L developing thrombotic events.(11)
- It is diagnosed by a HITTS screen.(12)
- The standard anticoagulants used in HIT are argatroban (not currently registered in Australia), and bivalirudin.(10)
- The UK Medicines and Healthcare products Regulatory Agency (MHRA) is undertaking a detailed review of the five cases of CVST with low blood platelets that occurred in the UK, and also notes that these events can occur naturally.(13)
Archive COVID-19 vaccines clotting disorders
Added: 30 Apr 2021
Evidence in brief on COVID-19 vaccines and clotting disorders
- 8 April 2021: ATAGI (Australian Technical Advisory Group on Immunisation) recommends that COVID-19 vaccine by Pfizer is preferred over AstraZeneca in adults aged under 50 years.(1)
- 8 April 2021:Therapeutic Goods Administration notes investigation of unusual thrombosis in Australian vaccine recipient points to likely association, but insufficient evidence for firm conclusion.(2)
- 7 April 2021: European Medicines Agency review of 62 cases of cerebral venous sinus thrombosis and 24 cases of splanchnic vein thrombosis concludes unusual blood clots with low blood platelets should be listed as very rare side effects with AstraZeneca. Most cases occur in women under age 60 within two weeks of vaccination, although some of this may reflect greater exposure of such individuals due to targeting of particular populations for vaccine campaigns. Overall benefits outweigh risks.(3)
- March 2021: Canada and Germany suspend use of AstraZeneca vaccine in people younger than 55 and 60 years, respectively. UK Government says it is preferred that people under 30 years be offered an alternative vaccine.(4-6)
- There are however, concerns around complications with other COVID-19 vaccines and these have received less attention.
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. Evidence checks are archived a year after the date of publication.