Welcome to the Otago Global Health Institute’s Covid-19 Masterclass Series. The series brings together a network of experts who over the next two weeks will discuss key topics such as: vaccination coverage and equity, mandates and ethics; advances in treatments and tests; and children and Covid-19. As the pandemic races towards an unenviable two-year milestone, we consider it vital that experts from multiple disciplines collaborate to help us understand the new landscape and inspire solutions.
After almost two years of the Covid-19 pandemic, researchers are now better placed to understand its impact. University of Otago experts Professor Philip Hill, Associate Professor Patrick Vakaoti and Professor John Crump outline what we have learned so far.
A pandemic with a massive global impact
With no prior specific immunity to SARS-COV-2, the virus that causes Covid-19, the whole human population was endangered. Covid-19 is easily underestimated, with only about 1 percent of unvaccinated infected people dying of the disease.
However, the combination of around 10 percent of those infected having a very serious illness, vast numbers of people becoming infected, and exponential growth of Covid-19 epidemics, led to disease ‘tsunamis.’ These overwhelmed even the best health systems, driving whole populations into lockdowns.
So, what are the main facts that we have learned about this global Covid-19 pandemic?
Age-specificity and comorbidities
Age-specificity of Covid-19 means that the severity of disease and mortality from the virus rise with increasing age. Mortality ranges from close to 0 percent among those under 10 years of age to more than 5 percent among those aged over 65 years. New Zealand has more 650,000 people over the age of 65 years.
Covid-19 disease outcomes are much worse for people with a pre-existing disease of relevance, such as diabetes, immunosuppression, obesity, high blood pressure and chronic renal disease. For populations with more of these comorbidities, such as Māori and Pasifika, those aged in their 50s have a similar risk profile to other populations aged in their 60s.
Public health responsiveness
Early in 2020 it became clear that some Asian countries were having success with public health measures against Covid-19, some even eliminating the disease. Elimination is not considered achievable according to influenza virus-based pandemic plans.
Analysis of the virus suggested that just diagnosing and isolating people with Covid-19 was of limited benefit, but if the person was diagnosed and their contacts ‘quarantined’ early enough, onward transmission could be prevented.
With the Delta variant, infectiousness is increased and the window of opportunity to identify contacts may be shorter compared with earlier SARS-CoV-2 variants, but it is still substantially longer than with influenza.
Rapid case contact management is most successful when it is high performing (against key indicators, such as time from case diagnosis to quarantine of their contacts) and there are other public health measures in place, such as raised alert levels.
Waves of outbreaks
Covid-19 tends to come in ‘waves’, which differ in the peak numbers of cases and in duration. These are dependent upon public health measures and human behaviour; new variants of the virus; and protection offered from vaccines.
As shown in the figure below, based on the experience of New South Wales, Auckland can expect a Delta wave to last four to six months and there may be a ‘long tail’ or even some resurgence.
Clustering
Covid-19 infections occur in clusters that arise in ‘contact networks’ such as households or other specific groupings of people. Large indoor gatherings are especially likely to be super-spreading events.
More rare transmission events help the virus to cross between contact networks. One feature is that, during an outbreak, large numbers of people can be infected while even larger numbers are not.
For example, while it appeared that the virus swept through the UK in the first Covid-19 ‘wave’, fewer than 20 percent were infected by the time they were driven into lockdown.
Effective vaccines and treatments
By the end of 2020, several effective and safe vaccines had been produced. This was made possible through established technologies, cooperation under urgency, huge public and private investment and by conducting phases of development in parallel.
The mRNA vaccines, such as the Pfizer-BioNTech vaccine, have consistently had the highest efficacy against Covid-19 disease compared to other vaccines.
Treatment has always been crucial to reducing mortality from Covid-19. Oxygen and intensive care can reduce mortality considerably. More recently it has been shown that dexamethasone, monoclonal antibodies and specific anti-viral drugs can also have an effect on mortality.
Waning protection
The immune response to SARS-COV-2 infection or vaccination wanes, especially with respect to the risk of becoming infected and transmitting the virus. But administering a booster dose reverses waning.
Because protection against the risk of severe disease has been relatively preserved to date, one could argue that booster doses should be reserved for immunocompromised people. If one wants to minimise the number of new infections then everyone should have a booster dose, as is planned for New Zealand.
From a global health perspective, rich countries could forego boosting while poor countries have low vaccine supply. Many African countries have less than 5 percent vaccination coverage.
An end in sight?
After the ‘acute phase’ of SARS-COV-2’s interaction with humans, large proportions of the world’s population will have been exposed to the virus and/or have been vaccinated. Following this, the virus may fade away. However, it is more likely to become endemic, whereby there is a relatively stable number of infections in the population.
If immunity did provide lifelong protection, then widespread effective vaccination could generate enough herd protection to allow for elimination. If endemic Covid-19 causes unacceptably high mortality, despite advances in treatments, developing improved Covid-19 vaccines could become a high priority.
Massive societal impact
The Covid-19 pandemic is relentless. The virus becomes stronger as we become exhausted. Covid-19 has increased ethnic, gender, and socio-economic disparities globally.
The economic loss from lockdowns and from the pandemic itself has been enormous. Businesses have closed, jobs lost, relationships strained, and dreams shattered.
Students in many countries have had almost no face-to-face learning. The virus has exposed leaders who underestimated it, distorted the truth to protect political capital, and announced ‘freedom’ without appropriate planning.
It is important that voices from multiple disciplines should provide perspectives as part of an integrated and optimal response to Covid-19.
Health problems are best solved by those most affected by them. This means that communities should be engaged in ways that help them understand the pandemic. In turn, communities and their own health experts should be actively involved in the solutions.
The many examples globally of individual and community resilience to Covid-19 demonstrate that there is hope for a better world beyond the pandemic.
Professor Philip Hill is co-director of the Otago Global Health Institute, and McAuley Professor of International Health in the Division of Health Sciences, at the University of Otago.
Associate Professor Patrick Vakaoti is co-director of the Otago Global Health Institute, and Associate Professor in Sociology, in the School of Social Sciences, at the University of Otago.
Professor John Crump is the McKinlay Professor of Otago Global Health in the Division of Health Sciences at the University of Otago.
