Australian experts respond to Pfizer vaccine announcement

Pfizer and BioNTech have issued a press release, announcing that their vaccine candidate is more than 90% effective in preventing COVID-19. The results are based on initial data from a large study of 43,538 participants, including 94 confirmed cases of COVID-19.

Australian health experts have described the interim study findings as promising, but caution that we must wait for the complete study data in the form of a peer-reviewed journal paper.

Associate Professor in Epidemiology at La Trobe University Hassan Vally said, “Although these results are early findings, they provide a welcome bit of good news.

“In essence, Pfizer report that the initial indication is that their vaccine is looking like it is 90% effective. That is, it protects individuals against disease 90% of the time. To put this in perspective, we have generally agreed that if we have a vaccine that is 50% effective, this will be good enough to proceed with.

“We probably need to be measured in our enthusiasm until the trial has been completed, but we would rather see these sorts of early findings than hear that the vaccine was not working as well as ... hoped.”

Public health physician and infectious diseases epidemiologist at the University of Queensland Associate Professor Linda Selvey added, “This announcement is very encouraging; however, it will not, on its own, mean that we will be able to resume ‘business as usual’ anytime soon.

“Pfizer has announced that they will be able to produce up to 1.3 billion doses by the end of 2021, which would be sufficient to vaccinate 650 million people. This points to the importance of having several vaccines available, in order to ensure that everyone around the world will be protected.

“An efficacy of 90% is encouraging, but, in the situation where there are no restrictions on gatherings or movement, this would mean that around 65% of the population would have to be vaccinated in order to stop circulation of the virus (assuming an R0 — reproduction number — of 2.5).

“It would be important to test the efficacy of the vaccine in more vulnerable populations, such as the elderly or people with compromised immune systems. If it is found to be very effective in these populations, it could be used to protect these people, with other vaccines with greater stability being used to vaccinate the broader population.”

Associate Professor Selvey also pointed to the logistical challenges for mass vaccination campaigns, commenting that the mRNA vaccine has to be stored at -70°C, and can only be stored at 4°C for 24 hours.

Professor Raina MacIntyre is Head of the Biosecurity Program at the Kirby Institute at the University of NSW. An expert in influenza and emerging infectious diseases, Professor MacIntyre said that the data needs to be seen in a peer-reviewed publication to fully evaluate it.

“They [the researchers] do not provide the number of cases in the vaccine arm vs the placebo arm, but we can assume that the majority of the 94 cases (out of the total 43,538 trial participants) that were the basis of the interim analysis occurred in the placebo arm.

“They also report that the vaccine trial has not picked up any serious side effects, and that the trial included diverse participants. It is important to have data on different ethnic groups, as the risk of disease does vary by ethnicity, although this is probably more related to socioeconomic factors than race.

“We also do not know duration of protection, or how long the protection lasts.

“Overall, this is very positive news and should give people hope that this and other vaccines will live up to expectations.”

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