Pearls and Irritations

The first week of June will be significant in Australia’s Covid story. Victoria had entered lockdown on Thursday 27 May after a case of community infection arrived via Adelaide. Another more dangerous variant would also appear. Australians would react with more heading out to get a jab, but not in sufficiently large enough numbers. Pressures were building for the government to dramatically change its vaccine strategy.

Here we explain why a move to high efficacy vaccines is necessary. While embarrassing for the government, it might be the good news amongst the bad (as explained in Part 4).

Change is being forced onto our decision-makers!

The ABC has an excellent webpage called Untangling Australia’s vaccine rollout timetable.

At the very beginning the link includes:

“We don’t want to make promises that we can’t keep. That is incredibly important,” Prime Minister Scott Morrison assured Australians in January.

The webpage notes that in the three months since the official launch of the vaccine campaign on February 22, the government has announced more than a dozen targets, revisions or updates to the rollout plan. The webpage has excellent graphics displaying how the rollout changed over those months. (The graphics are best viewed on a large screen.)

It was last updated on 30 May. It ends with:

As June approaches, the nation stands poised to pass the government’s 4-million-dose milestone — two months later than originally planned.

The vaccination rate has climbed to a record 535,000 doses a week.

At this pace, Australia can expect to reach the 40 million doses needed to fully vaccinate the adult population in September 2022.

On 15 June, the total number of doses administered had reached 5,888,718, an increase of 684,741 for that week, an improvement on May, but only 100,000 per day. Despite worrying developments about the Victorian outbreak and a new variant, the increase is not nearly enough: if it continued at this weekly rate until 40 million doses were delivered it would take 48 weeks, up to May 2022!

The daily rate might increase as second doses occur, but the finish line is not close. If we want to vaccinate our 5.5 million children as well (as some countries are starting to do), add a few more months.

The pointers are that Australia will have to switch to relying on Pfizer (and the higher efficacy Moderna and Novavax vaccines) due later in the year.

Because it has higher efficacy, has a space of only three weeks between doses and can be more readily upgraded for new variants, it makes sense that if more Pfizer were available there would be a jump in the uptake rate. An early indication is WA authorities being “bowled over” by the massive interest from West Australians aged between 30 and 49 in getting the Pfizer once it was opened to them.

The major reason for prioritising Pfizer though is because we need to cope with the Delta (Indian) variant, now the dominant strain in some countries. We are seeing headlines such as Why the Delta covid variant strain is terrifying experts and warnings that it spreads more easily, is more severe, and is more resistant to vaccines.

The strain is quoted as up to 70% more transmissible than the Alpha variant, and a major driver of infections in the young. With the strain apparently now in Australia, there was a significant shift in the federal government and National Cabinet’s objectives with now a push to vaccinate the young, group 2b, using the stronger Pfizer. The aim – to minimise transmissions.

This change in strategy is taken up in Part 4, where we demonstrate that it creates further problems, a vicious circle that can only be broken with a shift in vaccine strategy.

The problem of reaching herd immunity and opening our borders

The overall sum of these issues is that under current plans Australia will not reach herd immunity. The more virulent strains now seem to make it impossible to get there without switching to high efficacy vaccines.

This informative article was published in The Conversation on 15 February: Herd immunity is the end game for the pandemic.

The article explained the role of the basic reproduction number, R₀, a measure of the contagiousness of the virus which causes Covid. The R₀ for the original Covid strain was thought to be 2.5. That meant, on average, a person with Covid-19 would infect 2.5 people. The article explained how it was possible to use the factor to predict the level of coverage (vaccine uptake) required to reach herd immunity. The lower the efficacy of the vaccine the higher the uptake required to reach herd immunity as some people who are vaccinated can still become infectious and ill from Covid and some can also be asymptomatic, potentially spreading the disease.

Thus it concluded that to reach herd immunity with the original variant we’d perhaps only need to vaccinate 63% of the population with the Pfizer with its efficacy of 95%, or 67% if we used the Novavax with its efficacy of 89%. However, we would need to vaccinate almost 100% of Australians to achieve herd immunity with the AstraZeneca vaccine, with its efficacy of 62%. With a combination of the three vaccines it would still have been difficult.

With the Delta variant detected in Victoria’s outbreak, we learn that the R₀ for the Delta variant is thought to be 5.0.

The aforementioned article includes a very useful graph which we reproduce below. Note the curves for three different levels of efficacy. A dotted line is drawn up from the horizontal axis at the R₀ = 2.5 mark. The vaccination uptake levels required are shown on the vertical axis across from where the dotted line cuts the curves.

We have taken the liberty of adding a solid blue line to the graph at R₀ = 5.0. With a ruler you can draw your own conclusions.

Assuming the theory behind this graph is correct, it shows that to reach herd immunity Australia would need to switch to Pfizer (or equivalent) and achieve a vaccine uptake of close to 85%.

It is likely the government will move its focus to Pfizer (or equivalent)

Our decision makers will soon have to face up to whether or not to continue with AstraZeneca as our main weapon against Covid.

Various experts are expressing doubt about our current strategy and have indicated the need to switch to high efficacy vaccines (see the transcript of 7.30 on the ABC on the 10 June).

To add to the concerns, the ABC included this online article on what we know about the Indian Delta COVID-19 variant detected in Victoria’s outbreak. It indicated that AstraZeneca effectiveness against the Delta variant might be as low as 60 per cent.

Greg Hunt has been ‘all over everywhere’ on the matter of the Covid rollout. However, perhaps on 23 May he indicated the way forward when he announced that from the beginning of October we should have two million Pfizer doses a week, raising the possibility of vaccination by Christmas for those who want it. A few days earlier he had stated: “Right now, we want to encourage everybody over 50 to be vaccinated as early as possible … But we’ve been very clear that, as supply increases later on in the year, there will be enough mRNA vaccines for every Australian.”

In other words, he was telling Australians that if they had concerns about AstraZeneca, they could wait for a few months for the Pfizer or equivalent. (Of course, those who were happy to act earlier could still have AstraZeneca.)

The Minister was reprimanded by some fellow decision-makers for undermining the rollout with these statements, but it seems inevitable that the government will change its strategy. That is made even more possible as we hear that cold storage problems with Pfizer are being overcome making it more transportable with a longer shelf life, meaning it can be used in remote communities and be given in less sophisticated clinics, such as pharmacies.

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