Busting the myths about COVID-19 herd immunity, children and Lives vs Jobs

Image sourced from Pixabay

Raina MacIntyre March 28th 2020

We are in the midst of a pandemic, the likes of which has not been seen since 1918-19. A recurring narrative to justify the softly, softly approach to control of COVID-19 presents four false arguments:

  1. Allowing some transmission is good because it will create herd immunity and protect people.
  2. The infection doesn’t matter in children and young people because it is mild or asymptomatic
  3. The choice we face is between saving lives or jobs and case fatality rate is low
  4. Lockdown has to remain for 6-12 months

Some suggest we should allow young people to get infected by leaving schools open or allowing large gatherings of young people. We also hear that COVID 19 is not a problem for most people, and that young people don’t need to worry about it – which sends a mixed message about the gravity of the pandemic. We hear that it’s a choice between lives and the economy.

 

Myth 1: letting infection transmit will provide herd immunity: herd immunity is a concept related largely to vaccination programs. It is the observation that when enough people are immune to an infection, even people who are non-immune are protected because the number of non-immune individuals is too small for infection to spread.  To understand herd immunity, we must understand contagion, which is reflected in the value of “R0”, the basic reproductive number.  R0 is the number of secondary cases arising from one index case in a completely susceptible population (ie non-immune). The epidemic threshold is defined mathematically as when the R0 exceeds one.  If R0 is greater than one, conditions for an epidemic are present, although an epidemic may not always occur.  If the R0 is less than one, an epidemic cannot be sustained because one infectious case infects less than one other person on average, and infection will die out.  

All public health strategies which we use to control epidemics aim to drive the R value down below one, and thereby stop the epidemic. The R modified by vaccination, social distancing or other measures is called the effective R, or Rt. The aim of vaccination programs or “flattening the curve” is actually reducing the Rt.

Closely related to R0 is the concept of herd immunity.  Immunity can be gained by infection, or by vaccination.  The required proportion of people in a population that need to be immune to induce herd immunity (H) is related to the R0 and calculated by the formula H=1-(1/R0).

Credible estimates of R0 for COVID-19 lie between 2-3. If we take the value of 2.6, which has been accepted in Australia, using the formula above, we need 61% of the Australian population to be infected, recovered and immune to gain herd immunity for the remaining 39% of people.  An infection rate of 61% takes us into the catastrophic range, even worse than what we are seeing in Italy or the US right now.  The 61% is not achievable anyway, because over 50% of the population is aged over 40 years, so you would have to get people infected in older age groups. Finally, we are being told 20-60% of Australians will get infected and there may be 150,000 deaths. Why, in a high-income country of 26 million people, would we accept that, when China with nearly 1.4 billion people had less than 1% of their population infected, and 3298 deaths? I do not accept that, and we must to everything we can to make sure we do not get thrown into a worst-case-scenario. Allowing a disease to “rip” through a population will not get rid of it – it causes recurrent, cycling epidemics of a mass scale, as seen with measles, mumps, rubella, smallpox and all other epidemic infectious disease prior to vaccination. It is illustrated by the impact of vaccination on smallpox control, which stopped large scale recurrent epidemics. Unless we can eradicate an infection, vaccination is the only way to control it long-term. However, a range of non-pharmaceutical measures will also control epidemics, and can be used in the short to medium term to reduce the size of the epidemic, manage demand in the health system and save as many lives as possible.

Myth 2. Keep schools open because children don’t have a problem with COVID-19: Confident assertions that schools can remain open are not consistent with WHO recommendations for a serious pandemic (which state schools should be closed), nor with the stated desire to flatten the curve – a modelling study shows at least 80% of people need to stay home to achieve flattening of the curve. About 20% of the Australian population is aged <18 years, so it may be mathematically impossible to achieve flattening of the curve with phased, partial social distancing and schools remaining open.  The statement that “there is no evidence that children can spread the infection widely” is made on the background of few studies of COVID-19 in children, and with disregard for the concerning data we do have. In one study of over 2000 children, only 50% had mild infection, 30% had moderately severe illness, 6% were critically ill and a 14-year old died.  In another study which showed a similar spectrum of illness, a 10 month old infant died of COVID-19. In the US, a 17 year-old died after being turned away from hospital.   It is dangerous to perpetuate the myth about that COVID-19 is not serious in children and young people.

The fact is, we cannot confidently assert that it is safe to keep schools open in a pandemic, because our restrictive testing criteria do not give us information on transmission in children. We have not done population serosurveys, and have no data on serological indicators of exposure in children. There are no data which allow us to say that teachers are not at risk –and we are seeing reports of teachers becoming infected in Australia. In the US, a 36 year old school principal died of COVID-19.

Studies of respiratory transmissible viruses globally show that the most intense contact between people in societies is in children and young people. For this reason, we see the most intense transmission of most respiratory infections in younger age groups.  We have no basis upon which to say that there is low transmission in children, when we have not studied it or collected data, and when the data we do have suggest the opposite.  It may well be that children and young people are driving the epidemic through silent transmission.  The Director of Epidemic and Pandemic Diseases at WHO reported on Twitter that her 10 year old son got infected at school and then infected her husband. Many young people are also getting infected and seriously ill.

Viruses cannot be instructed to only infect healthy children and young people, so allowing transmission in schools will result in vulnerable people becoming infected and dying.  Many people live in multigenerational arrangements, so young people becoming infected could result in older people or people with chronic diseases becoming ill.  The messaging that the disease is mild in young people also encourages young people to have parties and other gatherings that transmit infection.

 

Myth 3: The death rate is low, and the choice we face is between saving old people’s lives or jobs

A common perception is that we are choosing between saving the lives of a few older people versus the jobs of younger people.  This view perceives the COVID-19 pandemic as mild, and the deaths as static and comparable with annual deaths from road traffic accidents or seasonal influenza. Already there are indications that cases and deaths are underestimated, even in the US.  Whether the death rate is 0.85% or 8%, this is orders of magnitude higher than seasonal influenza or even the 2009 pandemic.  The argument about deaths rates being lower because of identification of asymptomatic and mild cases is false, as there is no testing for asymptomatic infection with seasonal influenza, the usual comparator.  When did the US military ever have to send hospital ships and set up tent hospitals during seasonal influenza?  When did we ever have to use ice skating rinks as temporary morgues when bodies were piling up?  Anyone still promoting the false narrative of COVID-19 being a trivial illness is ignoring this evidence. In the US, 36% admitted to ICU were aged 45-64 years and 12% were aged 20-44 years. Deaths have been seen in all age groups above 18 years.

Death is usually from respiratory failure, and lives are saved by intensive care and mechanical ventilation. A key predictor of death is running out of ventilators and ICU beds, thought to have driven much higher death rates in Spain and Italy.  In contrast in China, large hospitals were built in a matter of days to ensure capacity to ventilate patients was not lost. In Italy and Spain, and maybe even in the US, older people may be refused ventilation if capacity is exceeded and younger patients are in need.  We have two separate models suggesting we may run out of ICU beds some time in April.

The other impact of health system overload is the infection of health workers, already vulnerable because of the failure to stockpile adequate personal protective equipment (PPE), thus further compromising the ability to respond. In the US, critical shortages of personal protective equipment forced health workers to use plastic garbage bags as gowns, with some dying. If beds are full with COVID-19 patients and half the health workers are infected, the ability to treat other serious conditions like cardiovascular disease will be reduced.

Allowing transmission to continue in young people will result in the epidemic peaking earlier, in a higher peak, and a larger number of cases. It may be large enough to exceed our health system capacity very rapidly. The jobs vs lives argument fails to consider the rapid, exponential growth of pandemics, the risk of health system collapse and the cascading failures they may cause, leading to possible collapse of societies.

The COVID-19 pandemic has also exposed critical supply chain effects in a globalised economy. Essential medicines, car parts, computers, phones, and even food supplies have been affected because of our high dependence on imports and low capacity for domestic manufacturing. In the US, 80% of medicines and a large proportion of medical devices including PPE, are produced in China. Experts estimate it will take years for the US to develop domestic manufacturing capacity to be self-sustaining. If the pandemic grows unchecked, the economic losses will be far greater. Without disease control, the economic impacts will be far worse, will last longer, and will make recovery more prolonged.

 

Myth 4: Lockdown has to remain for 6-12 months

I understand that some of the economic modelling which has informed decision making have used annual models and have not been capable of examining smaller period of lockdown.  Social distancing is especially important with COVID-19 because there may be people who are infected who do not have symptoms. This makes disease control much harder, and until we have a vaccine, all we have available in the toolkit is social distancing and travel restrictions, along with isolation of sick people and quarantine of contacts and return travellers. Studies show that school closure should be done early to be most effective. Even if we do not close schools, we can mandate online learning – we have technology and free online learning systems such as Moodle, so we can use these to provide education remotely. 

China has demonstrated the feasibility of a short lockdown followed by phased lifting of restrictions. The graph below shows the success of lockdown in China, implemented in Wuhan on January 3rd, while the epidemic was in the exponential growth phase.  Within 1 incubation period (2 weeks), cases start to fall. China began lifting restrictions on February 9th, just over 1 incubation period from the lockdown. They have continued to gradually lift restrictions, from a more manageable baseline position of fewer cases to track and contain, all within 8 weeks. At the end of that 8 weeks they are in greater control because they have far fewer daily new cases to deal with and can quickly identify and contact trace these. If the epidemic was allowed to grow, they would have lost control with thousands of new cases occurring daily.

Image removed.

Epidemic curve in China showing impact of lockdown

 

A lockdown is a temporary measure which if done simultaneously and completely will result in reduction of epidemic size, more manageable case numbers and a flattening of the curve so that health system capacity is not exceeded. China has shown that a short lockdown can be highly effective and can be relaxed safely in a phased manner. The only two countries to achieve flattening of the curve to date are South Korea and China. South Korea has achieved this with more targeted, short lockdowns but extensive testing. In countries that have restricted testing, used slow trickle measures and avoided lockdowns until late, such as Italy, Spain and the US, we seen failures in epidemic control.

A short, sharp lockdown of 4-8 weeks will improve control of the epidemic in Australia, reduce case numbers and bring us to a more manageable baseline from which phased lifting of restrictions and economic recovery can occur. If we fail to do this, we face continued epidemic growth, potential failure of the health system, and a far longer road to recovery. A comprehensive lock-down also buys time to scale up, by an order of magnitude or more, our capacity for rapid case identification and isolation, with extensive testing, and thorough tracking and quarantine of contacts aided by novel smart phone apps and related technologies, as deployed with great success in South Korea. For lockdown to successful in a short, sharp burst, it must be accompanied by scaled up testing capability and broadened testing criteria (including asymptomatic at-risk people) to ensure that every new case can be identified rapidly during the lockdown and in the follow up phase, when restrictions are lifted. Expanded testing will need a more flexible approach to solutions, including enabling domestic capacity to scale up, procurement from overseas or actively asking for help from another country who has achieved testing at scale.  Without such an improvement in the public health response capacity, there will almost certainly be a bounce-back of the epidemic as lock-down restrictions are lifted. We have examples of countries which have failed and succeeded, which can guide such a response.

Epidemic control is time critical, because epidemics rise exponentially. We need to throw everything we have at this one and hold the line until we can vaccinate people.  At the beginning of March, we had 29 cases, and by the end of the month, over 3000. For every case detected, there are other cases that are undetected, and silent growth of an epidemic that will not be apparent until it hits our health system.

There is no real choice available between jobs and lives – failing to save lives now will result in more net job losses and a longer recession. This pandemic is with us, whether we like it or not, and may change the world in ways we cannot yet imagine. A short lockdown must be accompanied by expanded testing, a financial aid package that is accessible and leaves no person in need; a mental health and domestic violence package with outreach capability; a communications and social engagement package and other required support.  Australia has abundant talent and creative thinkers – let’s mobilise them into task forces for each of these needs.

 

 

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