Why are we seeing more COVID cases in fully vaccinated people? An expert explains


Nathan Bartlett, University of NewcastleMany people are worried about reports of “breakthrough” COVID-19 infections overseas, from places like Israel and the United States.

A breakthrough infection is when someone tests positive for COVID after being fully vaccinated, regardless of symptoms.

The good news is most breakthrough infections usually result in mild symptoms or none at all, which shows us that vaccines are doing exactly what they’re supposed to do — protecting us from severe disease and death. Vaccines aren’t designed to protect us from getting infected at all (known as “sterilising immunity”).

People with breakthrough infections can go on to infect others. Preliminary evidence indicates immunised people can have high levels of virus in the nose, potentially as high as unvaccinated people.

However, if you’re vaccinated you’ll clear the virus more quickly, reducing the length of time you’re infectious and can pass the virus on.

Here’s why breakthrough cases are happening, and why you shouldn’t worry too much.

Waning immunity

Two studies from the United Kingdom suggest the immunity we get from COVID vaccines wanes over time, after about four to six months.

While the more-infectious Delta variant continues to circulate, waning immunity will lead to more breakthrough infections.

But the reduction isn’t large currently. Vaccine effectiveness is very high to begin with, so incremental reductions due to waning won’t have a significant effect on protection for some time.

Israeli data shows some vaccinated people are becoming ill with COVID. But we need to keep in mind Israel’s vaccine rollout began in December 2020, and the majority of the population were vaccinated in early 2021. Most are now past six months since being fully vaccinated.

Given most people in Israel are vaccinated, many COVID cases in hospital are vaccinated. However, the majority (87%) of hospitalised cases are 60 or older. This highlights what’s known about adaptive immunity and vaccine protection — it declines with age.

Therefore we’d expect vulnerable groups like the elderly to be the first at risk of disease as immunity wanes, as will people whose immune systems are compromised. Managing this as we adjust to living with COVID will be an ongoing challenge for all countries.

What would be concerning is if we started seeing a big increase in fully vaccinated people getting really sick and dying — but that’s not happening.

Globally, the vast majority of people with severe COVID are unvaccinated.




Read more:
COVID cases are rising in highly vaccinated Israel. But it doesn’t mean Australia should give up and ‘live with’ the virus


We’ll probably need booster doses

Waning immunity means booster doses will likely be needed to top up protection, at least for the next couple of years while the virus continues to circulate at such high levels.

Our currently approved vaccines were modelled on the original strain of the virus isolated in Wuhan, not the Delta variant, which is currently dominant across most of the world. This imperfect match between vaccine and virus means the level of protection against Delta is just a little lower.




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Because the level of effectiveness is so high to begin with, this small reduction is negligible in the short term. But the effects of waning over time may lead to breakthrough infections appearing sooner.

mRNA vaccines in particular, like Pfizer’s and Moderna’s, can be efficiently updated to target prevalent variants, in this case Delta. So, a third immunisation based on Delta will “tweak”, as well as boost, existing immunity to an even higher starting point for longer-lasting protection.

We could see different variants become endemic in different countries. One example might be the Mu variant, currently dominant in Colombia. We might be able to match vaccines to whichever variant is circulating in specific areas.

The dose makes the poison

Your level of exposure to the virus is likely another reason for breakthrough infections.

If you’re fully vaccinated and have merely fleeting contact with a positive case, you likely won’t breathe in much virus and therefore are unlikely to develop symptomatic infection.

But if you’re in the same room as a positive case for a long period of time, you may breathe in a huge amount of virus. This makes it harder for your immune system to fight off.

This may be one reason we’re seeing some health-care workers get breakthrough infections, because they’re being exposed to high viral loads. They could be a priority for booster doses.

Might unvaccinated kids be playing a role?

It’s unclear if children are contributing to breakthrough infections.

Vaccines aren’t approved for young children yet (aged under 12), so we’re seeing increasing cases in kids relative to older people. Early studies, before the rise of Delta, indicated children didn’t significantly contribute to transmission.

More recent studies in populations with vaccinated adults, and where Delta is the dominant virus, have suggested children might contribute to transmission. This requires further investigation, but it’s possible that if you’re living with an unvaccinated child who contracts COVID, you’re likely to be exposed for many, many hours of the day, hence you’ll breathe in a large amount of virus.

The larger the viral dose, the more likely you’ll get a breakthrough infection.

Potentially slowing the number of breakthrough infections is one reason to vaccinate 12 to 15 year olds, and younger children in the future, if ongoing trials prove they’re safe and effective in this age group. Another is to protect kids themselves, and to get closer to herd immunity (if it’s achievable).




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High priority: why we must vaccinate children aged 12 and over now


A silver lining

Breakthrough infections likely confer extra protection for people who’ve been fully vaccinated — almost like a booster dose.

We don’t have solid real-world data on this yet, but it isn’t surprising as it’s how our immune system works. Infection will re-expose the immune system to the virus’ spike protein and boost antibodies against the spike.

However, it’s never advisable to get COVID, because you could get very sick or die. Extra protection is just a silver lining if you do get a breakthrough infection.

As COVID becomes an endemic disease, meaning it settles into the human population, we’ll need to keep a constant eye on the interaction between vaccines and the virus.

The virus may start to burn out, but it’s also possible it might continually evolve and evade vaccines, like the flu does.




Read more:
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The Conversation


Nathan Bartlett, Associate Professor, School of Biomedical Sciences and Pharmacy, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.

COVID cases are rising in highly vaccinated Israel. But it doesn’t mean Australia should give up and ‘live with’ the virus


Maya Alleruzzo/AP/AAP

C Raina MacIntyre, UNSWIsrael has one of the highest COVID vaccination rates in the world, having fully vaccinated 78% 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% 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.

Herd immunity is much harder with Delta

Around 25% of Israel’s population is younger than 12, so the whole population vaccination rate is only about 60% (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.




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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% 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% 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.

Lifting restrictions too quickly

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% 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% 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% vaccination rate at which the federal government proposes to begin easing restrictions corresponds to about 56% 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.




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Let’s recap

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% of the whole population, not the 60% achieved in Israel
  • over 70% 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).

Reasons for optimism

There’s a good news story in one of the most highly vaccinated cities in the US, San Francisco, where over 70% 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.

What about children?

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.




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Lifting restrictions with only 60% 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.The Conversation

C 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.

Home quarantine for vaccinated returned travellers is extremely low risk, and won’t damage their mental health


Matt Dunham/AP/AAP

Gregory Dore, UNSWMany thousands of people need to return to Australia, and many at home wish to reunite with partners and family abroad.

A move away from a one-size-fits-all approach to quarantine is a way to make this happen — including home quarantine for vaccinated returnees.

The federal government implemented home quarantine over a short period in March 2020, before switching to mandatory hotel quarantine for returned residents and other incoming passengers.

But the considerably changed circumstances — most importantly, access to effective vaccines — calls for its reintroduction despite caution among politicians and the community.

The low rate of positive cases, and proven effectiveness of further safeguards to limit breaches, make home quarantine a persuasive strategy.

It’s worth remembering people who contract COVID, and their contacts, have successfully self-isolated at home since the pandemic began.

How will we make sure it’s safe?

There are several protective layers which would ensure extremely limited risk of home quarantine for fully vaccinated returned overseas travellers.

The first is requiring a negative COVID test within three days of departure, which is currently a requirement for all returnees.

The second is COVID vaccination. Recent studies indicate full vaccination provides 60-90% infection risk reduction. In cases where fully vaccinated people do get infected, these “breakthrough cases” are less infectious.

It’s also important to test returnees in home quarantine. A positive case would trigger testing of any contacts and may extend self-isolation.

Also, high levels of testing in the broader community can ensure early detection of outbreaks, enabling a rapid public health response to limit spread, if it did leak out of home quarantine.




Read more:
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The risk would be extremely low

Data from hotel quarantine in New South Wales, which takes around half of returned travellers in Australia, suggests home quarantine for fully vaccinated returnees would likely present an extremely low risk.

In 2021, NSW has screened around 4,700 returnees a week, with the proportion of positive cases detected during quarantine averaging around 0.6%.

From March 1, since vaccination has become more accessible, only eight of 406 positive cases were fully vaccinated.

Unfortunately we don’t have the overall data on how many returnees were fully vaccinated, but even if only 10-20%, this would equate to a positive rate of around 6-12 per 10,000 among the vaccinated. This is considerably lower than the overall rate of 66 COVID cases per 10,000 since March 1.




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If home quarantine was initially restricted to fully vaccinated returnees from countries with low to moderate caseloads, the rate would be lower again, probably less than five per 10,000.

If NSW increased their quarantine intake by taking an extra 2,500 per week from this population into home quarantine, it would equate to maybe a few positive cases per month, compared to around 120 cases per month in hotel quarantine. As vaccination uptake increases, this capacity could be expanded, with reduced hotel quarantine requirements.

Will people comply?

The enormous desire for stranded Australian residents, overseas partners and family of residents in Australia to return and reunite should ensure a high level of compliance with home quarantine.

Home quarantine has been successfully implemented in other countries with elimination strategies such as Taiwan and Singapore. Taiwan’s system was deployed rapidly and has 99.7% compliance. Singapore uses a grading system to enable lower-risk returnee residents to do seven days in home quarantine, with a negative test required for release on day seven.

Two major reviews of the hotel quarantine system — the Victorian government-commissioned Coate report, and the national review of hotel quarantine — recommended implementing home quarantine with monitoring technology, such as electronic bracelets. Their recommendations were made prior to the approval of vaccines.

Recent data suggests the current hotel quarantine system has harmful effects. Research published in the Medical Journal of Australia in April found mental health issues were responsible for 19% of all emergency department presentations among people in NSW hotel quarantine. It’s highly likely home quarantine would be more beneficial for the mental health of returnees.

What are the barriers?

Issues which would need to be sorted through include:

  • methods for determining how risky different countries are
  • how returnees can prove they’ve been vaccinated
  • how we would test returnees and home-based contacts, and how frequently
  • and how long home quarantine would be for.

But none of these are insurmountable, and small-scale home quarantine already exists in the ACT.

Health authorities could ensure returnees can collect their own COVID testing samples, for example by doing nasal swabs or collecting saliva themselves. This would reduce contact with health workers.

Home quarantine is undoubtedly being considered by major Australian COVID policy committees, along with other measures to enable a larger number of returnees and to increase the safety of the quarantine system.

Australians’ excessive caution continues to have direct consequences for the well-being of many thousands of stranded Australian residents, together with non-resident partners and family members desperate to return.

It’s time to change this situation and make their human rights a public health priority.


The author would like to thank John Kaldor, Esther Rockett, and Liz Hicks for their input.The Conversation

Gregory Dore, Scientia Professor, Kirby Institute; Infectious Diseases Physician, St Vincent’s Hospital, Sydney, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

COVID is surging in the world’s most vaccinated country. Why?


Houses in the city of Victoria, the capital of Seychelles.
Shutterstock

C Raina MacIntyre, UNSWThe small archipelago nation of Seychelles, northeast of Madagascar in the Indian Ocean, has emerged as the world’s most vaccinated country for COVID-19.

Around 71% of people have had at least one dose of a COVID vaccine, and 62% have been fully vaccinated. Of these, 57% have received the Sinopharm vaccine, and 43% AstraZeneca.

Despite this, there has been a recent surge in cases, with 37% of new active cases and 20% of hospital cases being fully vaccinated. The country has had to reimpose some restrictions.

How can this be happening? There are several possible explanations:

  1. the herd immunity threshold has not been reached — 62% vaccination is likely not adequate with the vaccines being used
  2. herd immunity is unreachable due to inadequate efficacy of the two vaccines being used
  3. variants that escape vaccine protection are dominant in Seychelles
  4. the B1617 Indian variant is spreading, which appears to be more infectious than other variants
  5. mass failures of the cold-chain logistics needed for transport and storage, which rendered the vaccines ineffective.

What does the country’s experience teach us about variants, vaccine efficacy and herd immunity?

Let’s break this down.

Variants can escape vaccine protection

There are reports of the South African B.1.351 variant circulating in Seychelles. This variant shows the greatest ability to escape vaccine protection of all COVID variants so far.

In South Africa, one study showed AstraZeneca has 0-10% efficacy against this variant, prompting the South African government to stop using that vaccine in February.

The efficacy of the Sinopharm vaccine against this variant is unknown, but lab studies show some reduction in protection, based on blood tests, but probably some protection.

However, no comprehensive surveillance exists in the country to know what proportion of cases are due to the South African variant.

The UK variant B117, which is more contagious than the original strain, became the dominant variant in the United States. But the US still achieved a dramatic reduction in COVID-19 cases through vaccination, with most people receiving the Pfizer and Moderna vaccines.

Israel, where the UK variant was dominant, also has a very high vaccination rate, having vaccinated nearly 60% of its population with Pfizer. It found 92% effectiveness against any infection including asymptomatic infection, and Israel has seen a large drop in new cases.

The United Kingdom has used a combination of Pfizer and AstraZeneca vaccines. More than 50% of the population have had a single dose and almost 30% are fully vaccinated. The country has also seen a significant decline in case numbers.

But there’s a current surge of cases in northwest England, with most new cases in the city of Bolton being the Indian variant. This variant is also causing outbreaks in Singapore, which had previously controlled the virus well.

Seychelles needs to conduct urgent genome sequencing and surveillance to see what contribution variants of concern are making, and whether the Indian variant is present.

If the South African variant is dominant, the country needs to use a vaccine that works well against it. Many companies are making boosters targeted to this variant, but for now, Pfizer would be an option. In Qatar, local researchers found Pfizer had 75% effectiveness against the South African variant.




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We need to use high-efficacy vaccines to achieve herd immunity

The reported efficacy of Sinopharm is 79% and AstraZeneca is 62-70% from phase 3 clinical trials.

Our research at the Kirby Institute showed that, in New South Wales, Australia, using a vaccine with 90% efficacy against all infection means herd immunity could be achieved if 66% of the population was vaccinated.

However, using lower efficacy vaccines means more people need to be vaccinated. If the vaccine is 60% effective, the proportion needing to be vaccinated rises to 100%.

When you get an efficacy of less than 60%, herd immunity is not achievable.

However, these calculations were done for the regular COVID-19 caused by the D614G variant which dominated in 2020. This has a reproductive number (R0) of 2.5, meaning people infected with the virus on average infect 2.5 others.

But the B117 variant is 43-90% more contagious than D614G, so the R0 may be up to 4.75. This will require higher vaccination rates to control spread.

What’s more, the Indian variant B1617 has been estimated to be at least 50% more contagious than B117, which could take the R0 to over 7, and takes us into uncharted territory.

This could explain the catastrophic situation in India, but also raises the stakes for vaccination, as lower efficacy vaccines will not be able to contain such highly transmissible variants effectively.

Herd immunity is still possible, but depends on the efficacy of the vaccine used and the proportion of people vaccinated.

A UK modelling study found using very low efficacy vaccines would result in the economy barely breaking even over ten years because it would fail to control transmission. On the other hand, using very high efficacy vaccines would result in much better economic outcomes.

Vaccinating the world is the only way to end the pandemic

As the pandemic continues to worsen in some parts of the world, the risk increases of more dangerous mutations that are vaccine-resistant or too contagious to control with current vaccines.

Keeping up with mutations is like whack-a-mole while the pandemic is raging.

The take-home message for our pandemic exit strategy is that the sooner we get the whole world vaccinated, the sooner we will control emergence of new variants.




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The Conversation


C 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.

We may never achieve long-term global herd immunity for COVID. But if we’re all vaccinated, we’ll be safe from the worst


Gideon Meyerowitz-Katz, University of WollongongIn early 2020, during the first thrashes of the pandemic, we were all talking about herd immunity.

At that stage, many commentators were arguing we should let COVID-19 rip through populations so we could get enough people immune to the virus that it would stop spreading. As I argued at the time, this was a terrible idea that would overwhelm hospitals and gravely sicken and kill many people.

Now we have safe and effective vaccines, we can aim to reach herd immunity in a much safer way. It’s certainly possible we’ll be able to reach and maintain local herd immunity in certain regions, states and countries. However the pandemic ends, it will involve this immunity to some extent.

But it’s still very uncertain whether long-term, global herd immunity is achievable. It’s quite likely the coronavirus could continue to spread even in places with high proportions of their populations vaccinated. It will probably never be eliminated.

However, if we’re all vaccinated, we’ll be largely safe from the worst ravages of the infection even if it does break out.

What is herd immunity again? And what does it mean for us long-term?

There are a few different definitions of herd immunity. Nevertheless, they all deal with the “reproductive number” of a disease, known as the R number. This is the average number of people an infected person will pass a disease on to, at a certain point in time.




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The R number depends on how infectious a disease is. Measles is often used as an example, because it’s one of the most infectious diseases. In a group of people among whom no one is immune to the disease, on average one person will pass measles on to around 15 others.

But as more people in the community become immune, either through vaccination or getting the disease and recovering, each infected person will pass on the infection to fewer and fewer others. Eventually, we reach a point at which the R number is below 1, and the disease starts to die out. The R number falling below 1 here is in a population where there are no social restrictions, so the disease starts to die out because of immunity and not because of measures like lockdowns. This is one definition of herd immunity.

However, another potential definition is that herd immunity is a state where enough people are immune in a population that a disease won’t spread at all. One of the more confusing parts of the pandemic is we scientists haven’t always used the same definition across the board.

For example, when we say “reached the herd immunity threshold”, we could be talking about a transient state where we’re likely to see another epidemic in the near future, or a situation where the vast majority of a population is immune and thus the disease won’t spread at all. Both are technically “herd immunity”, but they’re very different ideas.

How’s herd immunity calculated?

COVID-19 has an R number somewhere between 2 and 4 in groups of people where no one is immune. Using a simple mathematical formula, 50-75% of people need to be immune to COVID-19 for the R number to fall below 1 so it starts to die out, in a population with no social restrictions. Some researchers have done more complex versions of this calculation throughout the pandemic, but that’s the basic idea behind them all.

However, herd immunity is a moving target. For example, if everyone in your local population is taking great care to socially distance, COVID-19 won’t spread as much. Therefore, in practice, different cultures spread diseases to different extents, so the R number varies in both place and time.

Vaccines are the ultimate path to long-term immunity

Vaccines give us immunity against diseases, often to a greater extent than contracting the disease itself, and without the nasty consequences of being sick.

Our COVID-19 vaccines are safe and effective. Without going too much into the debate over which one is better, they are all capable of getting us to a point at which the disease would no longer spread through the community. For some vaccines, the percentage of people who we need to immunise is higher. But it’s the same basic idea regardless, and we need to vaccinate as many people as we can to have a shot at herd immunity.

We can already see this happening in some places. For example, in the United Kingdom and Israel, enough people have been vaccinated that even though restrictions are being relaxed, infection rates are staying low or continuing to drop. This is a beautiful sight.

The coronavirus will probably never be eliminated

Even with great vaccines, the problem is complex. There are almost always communities who aren’t immunised, for various reasons, even in countries with large proportions of the total population vaccinated. These small communities can continue to get sick and spread the disease long after the general population has passed the herd immunity line, which means there may always be some risk of COVID-19 outbreaks.

On top of this, new variants of the virus have emerged. Our current vaccines are probably enough to provide most people with immunity to the original strain in the long term. But several variants may substantially reduce our vaccines’ effectiveness as time goes by, so we may need boosters at some point.

What’s more, the global situation isn’t rosy. India and Brazil are currently experiencing horrifying COVID-19 outbreaks. The global case count continues to rise, partially because developed nations have hoarded vaccine doses jealously, despite this being a terrible approach to a pandemic. Rising case numbers anywhere increase the chances even more variants pop up, thereby impacting us all.

Even if we overcome vaccine hesitancy and global inaction, and we immunise most of the world, we may not be protected against the virus forever. Even higher-income nations may never get rid of COVID-19.

It’s quite likely this virus will never be eradicated (eliminated from every country across the globe). There may be places where the disease is gone, where local campaigns are successful, but there’ll also be places where the disease is still spreading.




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COVID-19 will probably become endemic – here’s what that means


What does this mean for Australia?

This presents a challenge for Australia. We have virtually no local COVID-19 transmission, so there’s no real risk from the virus as long as our border controls hold steady.

However, we probably can’t maintain this level of vigilance forever. And even with our very effective vaccines, we may not have long-term herd immunity — of any definition — to COVID-19.

At some point in the future, it’s likely we will see some cases of COVID-19 spreading in even the safest places in the world, including Australia.

Even so, getting vaccinated enormously reduces your risk of severe outcomes like hospitalisation and death. We should aim to vaccinate as many people as possible, while acknowledging that the future is inherently uncertain, and herd immunity is a challenging goal.The Conversation

Gideon Meyerowitz-Katz, PhD Student/Epidemiologist, University of Wollongong

This article is republished from The Conversation under a Creative Commons license. Read the original article.