Israel has begun offering third doses of the Pfizer vaccine to its at-risk, vaccinated population. The reason? Immunity in some vaccinated people is decreasing faster than in others, with herd immunity unlikely even after 90% of a population is fully vaccinated.
The heightened transmissibility of COVID-19’s Delta variant combined with gaps in the vaccines’ ability to fully prevent infection means variants will continue to be passed on from person to person. In Australia, this could have far-reaching implications when our borders reopen, with natural immunity low among the general population.
While herd immunity might be off the table for at least another year, booster doses of Pfizer could get us closer to that magic number — though Australia has already fallen behind Europe and North America in securing more supplies of the Pfizer vaccine.
The vaccine gap
The Delta variant is about 60% more transmissible than previous strains, with a reproduction number between six and seven — meaning an infected person will infect another seven people on average without social distancing precautions.
While both Pfizer and AstraZeneca are effective at preventing serious illness and hospitalisation, people can still catch and transmit the virus, often without symptoms.
Two doses of Pfizer is about 80% successful at stopping any Delta infection for those aged 16 to 60, while two doses of AstraZeneca is about 40% to 60% effective. Vaccinated people are 50% less likely to transmit the virus to others.
Monash University adjunct Professor Michael Georgeff told Crikey this means that once international borders open up, with vaccinated travellers able to visit without quarantining, the virus will spread. In 2019 there were 9.4 million international arrivals.
“Eventually it’s going to infect the number of people it’s going to infect … and it’s going to be very hard to prevent outbreaks,” he said.
If 85% of Australians were fully vaccinated with Pfizer, Georgeff estimated about four million people would eventually become infected, with COVID-19 hospitalisation rates matching hospitalisation rates for flu and influenza.
“Unvaccinated people are going to hospital between five and 10 times more than the vaccinated, and that’s what’s going to eventually blow the health system out of the water,” he said, adding that masks and social distancing would have to remain in place to ensure those infections are spread out over time.
This is already happening in the US and UK where, as restrictions are eased and quarantine-free international travel opens back up for vaccinated residents, there have been spikes in cases. In the week to Sunday, confirmed cases in the US rose to 136,351 — the highest weekly rise since April 2020.
Herd immunity unlikely
University of Melbourne epidemiologist Professor Tony Blakely told Crikey that even if Australia reached vaccination rates of 90%, herd immunity is still likely off the table.
“We’re not going to get there, particularly when you think viruses are going to mutate and probably become more resistant to the current vaccines,” he said.
Blakely says that, given Australia’s contact tracing methods had improved, the country could likely open up with 70% of the population vaccinated. The Doherty Institute is expected to release modelling on reopening borders in the coming weeks.
“When the virus gets in it will pop up here but it won’t take off like crazy … and some percentage of the Australian population will get naturally infected over the next couple of years,” Blakely said.
Fortunately, there’s emerging evidence a booster dose of Pfizer or other vaccines can protect against new strains and boost immunity as the body’s response to the vaccine wanes. But the global shortage of vaccines means this is a long way off for Australia. World Health Organization officials have called for countries to hold off on organising booster doses until other parts of the world have received doses.
Israel has begun offering third doses of the Pfizer vaccine to its at-risk, vaccinated population. The reason? Immunity in some vaccinated people is decreasing faster than in others, with herd immunity unlikely even after 90% of a population is fully vaccinated.
Bloody hell we have no hope as long as the Coalition and Berjiklian are at the helm.
Maybe labor could run on this platform
They couldn’t run on a platform at Central railway station at 3am.
The whole bleeding lot of them are useless.
Australia has already fallen behind Europe and North America in securing more supplies of the Pfizer vaccine.
FFS a direct result of Scovid’s preferring to deal with an ex Liberal staffer now lobbyists for AZ.
Rudd Labor got the end of year pfizer supplies brought forward to next month, two weeks away.
Sinner Morrisin made 55 calls on behalf of Mathias Fellow Conman to get a job, but unlike the Israel PM who made over 70 calls to pfizer, and other concerned PM’s, Scum Morrison made the big zero to pfizer. Rejecting the pfizer unlimited offer in June/July 2020, and only signing up in Nov 20 to a few million doses. Man’s a walking corruption pit.
There are currently 73 people in NSW hospitals being treated for COVID-19 with 19 of them in intensive care, five of whom are on ventilators.
Chant said that none of the patients in intensive care had been vaccinated.
Gee, whose fault is that!
I’ll worry about a booster shot once I have my 2nd dose, and I’ll worry about that once I have my first, and I’ll worry about that once my age group finally becomes eligible.
There’s a lot things that could happen between now and the time Australia is finally ready to consider boosters (other than for those in Sydney private schools who’ve no doubt got boosters scheduled before the rest of us are vaccinated), that it seems premature to wonder about what that world will be like.
Yes although I suspect the world will look ok whilst we’ll still be having this debate here in Oz wondering when we’ll be a part of the world again.
As Tonto said “Who you mean ‘we’?”.
Depends why it would be ‘a good thing’ that “we’ll be a part of the world again” – let’s watch Bozo’s Septic Isle this week when –
.. the winter of our discontent will be
Made glorious summer by this son of Pork;
And all the clouds that lour’d upon our house
In the deep bosom of the vaccinocean buried.
Now are lips with victorious wreaths of beer foam bound;
Our bruised arms hung up for monuments;
Apologies to Bill Wobblelance.
This ain’t over and will run & run in Peoria.
Interesting, so in your opinion we should remain a lone island in lock down at the bottom of the world? And this pandemic will run forever? Bit gloomy and unlikely in my opinion. Seen too many dystopian shows on Netflix?
PS although i do agree it will run for much too long in Australia, perhaps as long as poor third world nations.
Yes, that would be favourite. Let the world go to hell as it chooses, this country managed for its first 150,000yrs and when this brief interregnum finishes, will again.
May I recommend a neglected Australian classic?
Written during WWII and thus an entire chapter censored and not fully printed until 1983, “Tomorrow & Tomorrow” by M Barnard Eldershaw – a pseudonym of two women.
Ok I’ll take a look at Tomorrow and Tomorrow, but in your scenario of the world going to hell as it chooses, that hell may not bode well for Australia with its huge land mass and micro population.
In a world so chaotic I believe we would be in hellish circumstances as well.
Military advances make Australia’s isolation more of a disadvantage than an advantage.
Not good, lets not go there.
Two doses of Pfizer is about 80% successful at stopping any Delta infection for those aged 16 to 60, while two doses of AstraZeneca is about 40% to 60% effective.
Vaccinated people are 50% less likely to transmit the virus to others.
Pfizer? What’s that! That is the vaccine Scum made sure he received
Allan these figures have been debunked. Crikey reported it last week. Pfizer efficacy was formally established pre delta variant. AZ was established in the midst of delta. Apple’s for apples they are roughly equally effective.
…umm,”…they are roughly equally INeffective.” TFIFY.
If this were a Labor, or even “Labor”, government Moloch’s myrmidons would already have stories filed, ready to run & rave for when the fully vaccinated start coming down with C19 after who knows how long gaily shedding ‘viral particles’ far & wide.
I’m minded to paraphrase the old M.A.D. Cold war quip “the fully vaccinated will envy the dead” whilst the anti-vaxxer brigade care for the long covid cases…, as if.
Hysterical nonsense. Real world evidence is highlighting how vaccinated people are now NOT reporting to hospitals in the US and how it is unvaccinated people suffering.
We need to encourage unvaccinated people using real world evidence of the benefits of vaccination.