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.




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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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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.