Coronavirus Vaccine Policy in Australia

[tcpip]

The desperate decision of the Morrison government in Australia to panic and secure an additional 10 million doses of the Pfizer/BioNTech coronavirus vaccine is not just a case of "too little, too late", but also one of policy failure through continuing indifference. To give a summary of the current state of play, Australia is the only continent (apart from Antarctica) that has not implemented SARS-COV-2 vaccinations, leaving it far behind most advanced economies in distribution. It has, however, secured agreements for the production and supply of four different vaccines. Border workers, quarantine workers, some healthcare workers, and those who live and work in residential and aged care will receive priority Pfizer/BioNTech vaccines. The majority of Australians will receive the University of Oxford/AstraZeneca vaccine instead.

The difference between the two is in their relative efficacy, their ability to reach a Herd Immunity Threshold (HIT), and price. To put simply, Pfizer/BioNTech vaccines is the most effective (c95%) but also the most expensive, with US prices at $20 per dose. Oxford/AstraZeneca is estimated at 70% effectiveness, with US prices at $4 per dose. A significant cost issue of the former is a requirement that it is stored at temperatures between -80 and -60 °C until five days before vaccination when it can be stored at 2 to 8 °C. The University of Oxford/AstraZeneca has normal cold storage requirements. Part of the cost is that AstraZeneca's has a commitment to COVAX, a global initiative that aims to distribute low-cost vaccines to low- and middle-income countries.



With regards to Pfizer/BioNTech this vaccine is based on the use of nucleoside-modified mRNA (modRNA) technology. Such vaccines are non-infectious, as they do not require construction from an existing pathogen. Further, unlike protein vaccines, the mRNA is translated into the cytosol, removing the need for the RNA to enter the cell nucleus, and as such the risk of being integrated into the host genome is removed. The vaccine encodes part of the spike protein found on the surface of SARS-CoV-2 that generates an immune response, a process that requires two doses. Phase III clinical trials indicate an efficacy of 95%, with little variation among age groups (including adolescents). It has also shown effectiveness against some new strains.

In contrast, the Oxford/AstraZeneca is a modified version of an adenovirus, which causes the common cold in chimpanzees but rarely infects humans, and has been modified to ensure that the chimp virus cannot grow in people. The modified virus is used as a vehicle for the S-protein of the SARS-CoV-2 virus, acting as a primer to train the immune system. A curious aspect of the Phase III clinical trials for Oxford/AstraZeneca is their significant variation originating from a dosage error; an accidental half-dose followed by a full dose has a much better result (90%) than the standard two full-dose application (62%). A number of European countries have recommended against using Oxford/AstraZeneca vaccine in the elderly due to insufficient trial data.

These matters are of critical importance when considering the capacity of the vaccines to reach a Herd Immunity Threshold. To provide some basic epidemiological definitions, herd immunity is the resistance of a group of people to an attack by a disease to which a large proportion of the members of the group are immune, whether through vaccination or exposure. A herd immunity threshold (HIT) is reached when herd immunity is greater than the rate of infection, R_0; that will result in a decline of infection rates. What is the rate of infection of SARS-COR-2? That depends very much who one mixes with, and how, with significant variation in reported values. Australia, through state-based leadership and movement restrictions, has reduced the R_0 value to low levels. The probability of keeping that in place after a vaccination roll-out will be difficult, to put it mildly. Most people will believe that now that they are vaccinated, there will be no justification for movement restrictions. The problem is further complicated by the lack of plans to immunise children and adolescents, despite them being a vector for transmission.

Certainly, that should be the case and would be the case if Pfizer/BioNTech had been the main vaccine. However, it is the choice of the Federal government to emphasise Oxford/AstraZeneca means a second-rate vaccine for most people, even if backed by Pfizer/BioNTech for priority workers (which of course includes the Prime Minister). Now, there is no doubt that this multi-vaccine, layered, the approach might work, and it is planned in other countries as well, such as New Zealand which has achieved even better current R_0 values. It is little wonder that Australian epidemiologists raised the alarm, and the probably why the Federal government has engaged what looks like panic buying. To reiterate the introduction, the Australian Federal government has lagged behind the rest of the advanced economic world when it comes to deploying a vaccination programme. The Australian Federal government has also placed too much emphasis on an adenovirus vector vaccine, rather than a mRNA vaccine, resulting in the need to continue movement restrictions. This, of course, will result in continued economic damage and possible outbreaks, especially as international travel is re-opened. Given previous behaviour, it is expected that the Federal government will lay blame on the States for such decisions. In reality, the poor policy choices are theirs.