Latest on COVID-19
This week’s expert:
A/Prof Sanjaya Senanayake, Infectious Diseases Physician, Australian National University, Canberra
Drawn from Dr David Lim’s interview with A/Prof Sanjaya Senanayake on the Healthed Podcast, ‘Going Viral’.
• It is important to remember there have always been cases of community transmission of COVID-19 in Australia even before these latest outbreaks in Victoria and NSW
• It appears a small number of cases are responsible for the majority of transmission in these latest outbreaks. It is estimated that 10-20% of cases are responsible for 80-90% of the transmission, lending weight to the theory that some individuals are ‘super-spreaders’.
• Rather than the SARS-CoV-19 becoming more infectious, it is more likely these clusters are the result of a combination of a ‘super-spreader’ individual and increased complacency with regard social distancing.
• Recent surges in cases of COVID-19 are an important reminder of the need for containment measures to prevent transmission as we still don’t have medications to cure this illness or a vaccine.
• Maintaining restrictions to prevent transmission becomes more challenging over time. As health professionals we need to remind patients of the risks associated with this virus. Even younger people who are less likely to become seriously ill should they contract COVID-19 need to recognise the implication of becoming infected in terms of transmission to more vulnerable groups and triggering further community restrictions.
• Latest evidence suggests that transmission of SARS-CoV-2 is predominantly droplet, although it can be aerolised in certain circumstances. This evidence supports the use of facemasks to reduce transmission.
• In general, the body mounts a better immune response after contracting a viral infection than after a vaccine but this is not always the case. Scientists are waiting to see what happens with regard immune response post-COVID-19 infection vs vaccine.
• A recent study showing only 17% of patients still had antibodies to SARS-CoV-2 three months post-infection does not necessarily prove that post-infection immunity is short-lived. Antibodies represent only one type of immune response. T cell response can also confer immunity and this was not measured in this study. It is also possible that despite the lack of antibodies on testing, the body would mount an effective immune response should they be exposed to SARS-CoV-2 again, in the same way as people vaccinated against Hep B sometimes show no antibodies but have been proven to be immune to Hep B infection.
• However, if the finding that COVID-19 immunity is short-lived is correct, it is possible that boosters following vaccination may be necessary to ensure sustained immunity.
• Unrestricted international travel is unlikely to resume for Australians any time soon.