Australia plans to begin relaxing restrictions once 70% of over-16s are fully vaccinated. But as Israel shows us, it’s likely not enough to reach herd immunity, especially with the Delta variant.
Israel has one of the highest COVID vaccination rates in the world, having fully vaccinated 78 per cent of people 12 years and over.
Many people are surprised at the country’s resurgence of COVID cases since restrictions were lifted in June.
Israel’s vaccination rate is similar to Australia’s plan to start relaxing restrictions when 70 per cent of over-16s are fully vaccinated.
So, why are cases surging in Israel? And what can Australia learn from it, particularly as Sydney charts its path out of the pandemic?
Let’s break it down.
Around 25 per cent of Israel’s population is younger than 12, so the whole population vaccination rate is only about 60 per cent (including a small proportion of children under 12 with high-risk medical conditions who’ve also been vaccinated).
Even with last year’s virus and the use of the Pfizer vaccine, that wouldn’t be enough for herd immunity.
Read more: COVID is surging in the world's most vaccinated country. Why?
The Delta variant, which has swept the world since April, is much more contagious. It has an R0 of 6.4, which means one infected person on average infects more than six others in the absence of restrictions and vaccinations. This is compared to the strain circulating in 2020, responsible for Melbourne’s second wave, which had an R0 of 2.5.
In Israel, 60 per cent of hospitalised cases are vaccinated. This is something called the “paradox of vaccination” — in highly vaccinated populations, most cases will be in the vaccinated because no vaccine is 100 per cent protective.
However, the rate of serious cases in Israel is double for unvaccinated under-60s and nine times higher for unvaccinated over-60s, so vaccines remain highly protective against severe outcomes.
What’s clear in Israel (and the United Kingdom and United States) is lifting all movement restrictions and mask mandates after Delta arrived resulted in surging cases. Current vaccines at about 60 per cent uptake weren’t enough.
In the US, Southern states with lower vaccination rates are seeing the worst surges, with the majority hospitalised being unvaccinated. Alabama, with 36 per cent fully vaccinated (higher than Australia) is overwhelmed. Hospitals and ICUs are full and the health workforce is in crisis due to infected and quarantined health workers.
It provides a glimpse of what Sydney faces if we lift restrictions without the population being adequately vaccinated.
And that includes children. In Texas, paediatric ICUs are full and children cannot get beds. This is another warning that we must urgently vaccinate children, at least those 12 years and over, before lifting restrictions.
In Australia, the 70 per cent vaccination rate at which the federal government proposes to begin easing restrictions corresponds to about 56 per cent of the total population vaccinated.
It was modelled on 30 cases at the start of a new outbreak. With Sydney likely facing daily new cases in the 1000s (with no change in strategy), the outcomes could be much worse than anticipated.
So, the situation in Israel is caused by several factors:
the Delta variant has some ability to escape the protection offered by vaccines, and the protection seems to wane a bit over time after two doses
premature lifting of restrictions
the herd immunity threshold required for Delta is higher, likely over 80 per cent of the whole population, not the 60 per cent achieved in Israel
over 70 per cent of infections with Delta arise from asymptomatic transmission, which makes it harder to control
cases of Delta breakthrough infection in vaccinated people can be as infectious as in unvaccinated people (though viral load declines faster in vaccinated people).
There’s a good news story in one of the most highly vaccinated cities in the US, San Francisco, where over 70 per cent of the whole population has been vaccinated and cases are starting to decline.
This is also likely due to the reintroduction of layered social measures such as mask mandates.
Israel has reintroduced a green-pass system of proof of vaccination or a negative test for anyone three years or over accessing public indoor spaces. It has also started vaccinating over-50s with a third dose booster.
It seems a third dose dramatically boosts immunity, even in people with weakened immune systems. The US will soon start offering a third dose for everyone.
Many vaccines require three doses for full protection, and it’s too early to know what the final primary immunisation schedule will be. We may end up needing three doses plus regular boosters, or more effective spacing of two doses.
There’s reason to be optimistic because the vaccine pipeline isn’t static. We’ll have vaccines updated to tackle Delta and other variants in time, which will raise their efficacy and lower the herd immunity threshold.
In addition to crippling outbreaks of Delta in schools, new data shows kids 0-3 years old transmit to adults more than older children.
Ultimately, vaccination of children will be required to fully control SARS-CoV-2, or it will become a pandemic of the young, with unknown long-term, generational health effects for our children.
COVID has mutated to become more contagious, more vaccine resistant and more deadly. As a result, there’s no safe “living with COVID” until at least 80% of the whole population is vaccinated, including boosters or vaccines updated to tackle the Delta variant.
We can live with COVID as we do with measles — occasional travel-imported outbreaks that never become sustained — with an ambitious vaccination strategy.
Lifting restrictions with only 60 per cent of the population vaccinated in Australia will result in a resurgence of COVID like Israel, the UK or the US. The health system will be endangered and its workforce will be stricken.
To lift restrictions safely, we should also continue some social interventions such as wearing masks, vaccinating children, ventilating public venues including classrooms, and prioritising front-line health workers for a third dose booster to protect them and the health system.
There’s light at the end of the tunnel. But we need to keep using masks and other restrictions for now, learn from Israel and other countries, protect health workers and hospitals, vaccinate kids, use boosters, await vaccines updated for variants, implement smarter dosing schedules and aim for the most optimal vaccination strategy with equitable vaccine access, everywhere.
Raina MacIntyre, Professor of Global Biosecurity, NHMRC Principal Research Fellow, Head, Biosecurity Program, Kirby Institute, UNSW
This article is republished from The Conversation under a Creative Commons license. Read the original article.