Vaccine likely to prevent Covid developing but not stop transmission

<span>Photograph: Graeme Robertson/The Guardian</span>
Photograph: Graeme Robertson/The Guardian

It is unlikely that the first generation of Covid-19 vaccines rolled out in Australia in 2021 will prevent virus transmission, making ongoing high levels of testing, strong contact tracing, isolation, and quarantine crucial, a review commissioned by the Australian Academy of Health and Medical Sciences has found.

The academy comprises more than 400 senior researchers, and the review outlines steps for Australia’s pandemic response into the new year. It was authored by the director of the Marie Bashir Institute for Infectious Diseases Prof Tania Sorrell and University of Queensland immunologist Prof Ian Frazer.

“Announcements of interim results from vaccine trials are promising, but even a vaccine that is 90% effective at reducing disease will take time to manufacture, distribute and administer, and may have limited impact on SARS-CoV-2 [Covid-19] transmission and spread, or protection may be short-lived,” the review says.

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“Australia’s comprehensive Covid-19 public health measures and management approach will therefore remain crucial to the ongoing response.”

Data from vaccine phase 3 clinical trials to date show the vaccines lessen or prevent the vaccinated person from developing disease, but not whether they stop the vaccinated person from transmitting the virus to others. Whether vaccines also stop transmission is unlikely to be known until they are rolled out to the general population.

That’s why ongoing monitoring of those who are vaccinated will be critical, Sorrell and Frazer write, saying national control of the pandemic will depend on “sustained and enhanced support for research and innovation to continue to deliver the knowledge and tools required to tackle the pandemic – even when case numbers are low”.

“Additionally, current trials will not detect rare side-effects, those that occur in the longer-term, or those associated with specific population groups, because they do not involve enough participants. Such data will only become available after several months. The academy supports the position of the US Food and Drug Administration, which has said that issuing emergency use authorisation for a vaccine requires monitoring of data from at least half of the phase 3 trial participants for at least two months after vaccination and that further trial data [is] to be provided beyond this timeframe.”

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Frazer said vaccines will take “an enormous effort” to manufacture, transport, store and administer across the country. “And that is going to take a lot of time – very likely, deep into 2021,” he said. “If we let our guard down before that, the virus will get away from us again.”

The review states that lockdowns in response to outbreaks should be “a measure of last resort”. Managing mental health impacts of the pandemic will be crucial, the review says, as “the pandemic has generated feelings of anxiety and distress within the general population”.

“There is already evidence of more people developing mental health problems for the first time, increased relapse rates in those with previous mental illness and for some, an exacerbation of their existing mental illness,” the authors wrote.

“We are also seeing delays in seeking or obtaining care for other conditions such as stroke, myocardial infarction, cancer and acute surgical conditions, some of which are time sensitive and there is evidence that delays in presentations with these conditions impact morbidity and mortality.”

Sorrell, who chaired the report, said: “By any global measure the Australian approach has been a spectacular success.”

“But this has come at significant cost and, as the second wave in Victoria showed, success can be very fragile.”