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Will COVID-19 become endemic?
As it has been over a year since the World Health Organisation (WHO) announced the beginning of the COVID-19 pandemic, many of us are beginning to look forward to a reduced spread of the virus. With the rollout of several effective vaccines and the enforcement of safety measures such as travel bans and quarantine, coronavirus cases are reducing in some parts of the world.
One question that many people are wondering is whether it will be possible to eliminate COVID-19 or whether will it always remain endemic in some regions. We asked 8 experts in epidemiology ‘Will COVID-19 become endemic?’ 75% said ‘yes’, here is what we found out…
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Will COVID-19 become endemic?
What does endemic mean?
Endemic “means that there are always people who are infected, who pass infection to somebody else and then recover. Over a long time, each person infects on average one other person, so that the number infected remains approximately the same” says Professor Graham Medley, an expert in disease modelling from the London School of Hygiene and Tropical Medicine. This is very different from the high level of transmission we have seen during the pandemic.
Many common diseases are endemic, including the coronaviruses that cause colds. Prof Medley says “endemic infections are usually in children causing mild symptoms. Endemic coronaviruses are not associated with significant disease. By the time children are adults they will have been exposed, and potentially infected, many times, and are immune.”
How have previous pandemics ended?
Professor James Wood, an expert in disease modelling and epidemiology from the University of New South Wales, says “when pH1N12009 (swine flu) emerged in 2009, it became endemic within a year of the initial pandemic and also pushed the existing H1N1 influenza strain circulating in humans to extinction.” Many viruses that were responsible for previous pandemics, including the 1918 flu pandemic, are still circulating today.
Completely eradicating a disease is not easy. To date, the WHO has only declared two diseases that have been eradicated worldwide: smallpox and rinderpest. Both required a large, worldwide vaccine campaign to reach herd immunity.
The two options for how a pandemic can end either the virus is eradicated, or it becomes endemic.
Could we eradicate COVID-19 using the new vaccines?
Smallpox and rinderpest were eradicated using vaccines, now that several COVID-19 vaccines exist, could we use them to wipe out this disease?
Dr Lee Riley from UC Berkeley highlights one key obstacle to eliminating COVID - the responsible virus could mutate to become resistant to the vaccines. He says “In places where there is a mixture of vaccinated and unvaccinated populations, the vaccines may exert selective pressures on the virus to undergo further mutations, and these variants will spread among the unvaccinated people. Some of the variants may also infect vaccinated people.”
Another difficulty in reaching herd immunity is that some of the currently available vaccines do not offer 100% immunity against getting COVID-19. Professor Jane Heffernan, an expert in epidemiology from York University, says “COVID-19 infection and vaccination can induce high levels of protective immunity in individuals. The immunity gained can protect against infection, or, if infected, will lessen the severity of disease.”
There is also the challenge of vaccinating so many people across so many countries. Professor Wood from UNSW University highlights “the limitations in our ability to produce vaccine (15-20 million doses per day) mean that high global coverage with 2 doses will take well over a year even with relatively equitable supply of vaccines.”. Dr David Hayman from Massey University adds that “There is enormous inequality in vaccine distribution, with just a few percent of the world currently vaccinated. This means that unless this is resolved the virus will likely become endemic in those countries.”
Despite these challenges, it could still be theoretically possible to vaccinate enough of the world’s population to reach herd immunity and eradicate COVID-19. Interestingly, however, Professor Wood points out that “elimination and eradication may not remain as priorities if residual protection from vaccines against severe disease remains strong”. If we can protect people from becoming severely ill with COVID-19, there may be no reason to eradicate it completely.
Whilst public health measures and vaccine campaigns will hopefully end the current COVID-19 pandemic, it is likely that it will remain endemic in some countries rather than being totally eradicated.
May the facts be with you!
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