Are reduced adverse events worth the costs of delays in achieving COVID-19 herd immunity?

By Sam Lovick

Published in the Australian Financial Review 13 April 2021

Could we be about to see the Commonwealth government turn a silk purse into a sow’s ear? Their latest pronouncement on vaccination could do just that.

The Commonwealth government, with the assistance of the States and the acquiescence of a patient and compliant population, has managed to stem the worst effects of the global pandemic. They have done this by, in essence, closing the borders, injecting vast amounts of liquidity into the economy by subsidising jobs, and riding the resurgence of commodity prices. In large part these have offset the disastrous effects of the pandemic on education and tourism.

At the same time, they put in place plans for four COVID-19 vaccines, two from domestic sources, two (and a half) from overseas. The University of Queensland candidate fell over in trials. Imports have been less than anticipated leaving the CSL/Seqirus manufactured Astra Zeneca Oxford vaccine as the best candidate for vaccinating the Australian population quickly.

Now, we hear, that the AZ vaccine may cause blood clots so will only be given to those over 50. The Commonwealth is looking to buy more of the Pfizer vaccine to make up for the shortfall assuming, of course, that they can get it out of Europe. If they follow through with this (or if they don’t, and the under-50s are scared off the most abundant vaccine), then effective vaccination of the Australian population will be delayed.

If we were in normal times comparing two ‘normal’ vaccines with different adverse events profiles, we might choose to use only the vaccine with the better safety profile. But this is not normal. Time is of the essence. We should (if the safety profiles are tolerable) use any and all vaccines to cover our population, then the global population, as quickly as possible.

In 1918, the Spanish influenza pandemic started with fairly typical flu outbreaks in military camps in the US. It was just the flu. Six months later, it had mutated into a planet killer. Perhaps 4% of those infected died with a disproportionately high death rate in young adults; COVID-19 is a relative picnic in comparison. SARS does not mutate as fast as flu, but it does mutate. While there is a large body of infections globally, we all run the risk of a more virulent variant with faster transmission against which vaccines are less effective.

The economic costs of the pandemic to Australia remain enormous. Burgeoning debt, stagnant wages growth, moribund tourism and education, Qantas international grounded. For all the talk of strengthening domestic supply chains to avoid future pandemic fallout, Australia is a trading nation and needs to reopen its borders and its travel links to the rest of the world. With our zero tolerance for COVID deaths, we cannot realistically expect this until vaccination delivers something close to herd immunity. Even then, we may only be willing to fully open our borders to countries that have similar vaccination rates.

Our modelling suggests we need vaccination rates over 70% to achieve herd immunity. The slower our domestic program, the longer this will take. If the under 50s, who can still catch COVID, are scared off, we may never get there. If we don’t achieve it, and some of our over 65s fail to get vaccinated for whatever reason, one in five of them that catch COVID could die. Do we then close the borders for perpetuity?

Let us look at the numbers to get some perspective. I have heard reports of around 6 cases of cerebral blood clots per million AZ vaccinations. By way of comparison, there are between 2 and 5 cases per million of population every year anyway. And each year, between 30 and 100 women per million using the contraceptive pill can expect blood clots. While it is difficult to get a true assessment of relative safety of pandemic vaccines in the midst of mass roll out when severe adverse events are so rare, by any sensible standard they are very safe.

But suppose the AZ vaccine does increase the risk of blood clots and suppose the mRNA vaccines do not. If we vaccinated everyone in Australia with the AZ vaccine, we would expect 156 more cases of blood clots. Suppose, worst case, that each of those was fatal, a cost to the economy of approximately $5m each, or $780m in total. That is just over half the costs of the $1.2bn domestic travel subsidy program the government has just put in place!

In the pandemic to date, the government has pumped $200bn into the economy, about $16bn per month. If we really don’t want to give the AZ vaccine to the under 50s and this delays our vaccination program by just one month, does another $16bn goes on the bill? Isn’t $720 million (at the very worst) to manage 156 adverse events better value for money?