A creative rendition of SARS-CoV-2, displaying 3D prints of the virus and a background image that is a colorised scanning electron micrograph of a cell (red) infected with the omicron strain (blue). Image: NIAID/Flickr, CC BY 2.0
- Easing restrictions, resumption of air travel, the disappearance of masks and the celebration of festivals create a sense that the COVID-19 pandemic is on its way out in many countries.
- The unique biology of SARS-CoV-2 and the transient nature of infection- and vaccination-induced immunity have ensured its continued presence.
- Nearly 30% of the world’s population is still unvaccinated. Together with the lack of the transmission-blocking capacity of the current COVID-19 vaccines, the virus still has many more susceptible hosts.
- As a result, we can’t rule out the emergence of newer and potentially more worrisome variants, which in turn carries the possibility of prolonging the pandemic.
- Many scientists believe that the pandemic will transition at an unknown time in future to a state of relatively low-level persistence, known as the endemic phase. This is a likelihood, not certainty.
Since its emergence in late 2019, the SARS-CoV-2 pandemic has caused more than 630 million infections and 6.5 million deaths worldwide.
Unprecedented efforts and novel technologies have resulted in the creation and emergency use of several COVID-19 vaccines in record time. About 5.5 billion people, representing approximately 70% of the world’s population, have received at least one dose of a COVID-19 vaccine.
Currently, infection rates are steadily declining, as indicated by a basic reproduction rate[footnote]The average number of new infections arising from a single infected person[/footnote] of less than 1 at the global level. The latest variant, omicron, also appears to cause disease of relatively milder severity.
This has led to many countries around the world relaxing travel restrictions starting earlier this year. In tandem, governments have also been rolling back public health measures related to surveillance, testing, self-isolation, masking and socialisation. Global travel is picking up briskly and is poised to reach pre-pandemic levels soon.
All these signs have induced a sense that the pandemic is finally on its way out – but many scientists believe otherwise. If COVID-19 fatigue drives many countries to prematurely declare an end to the pandemic, there will likely be a heavier price to pay in terms of unnecessary (in the sense of being avoidable) loss of life.
In mid-September this year, the director-general of the WHO said that the end of the pandemic was in sight. The pandemic is waning, but by no means over. Worldwide, there are close to 1,500 COVID-19 deaths daily, of which nearly a 1,000 are from the US and Europe combined. The COVID-19 virus is still very much around.
There still being around 2.5 billion unvaccinated people worldwide means there is a lot of opportunity for the virus to spread and mutate, spawning variants that spread more efficiently and evade our immune defences more effectively, essentially prolonging the pandemic.
Now, the pandemic is poised to enter the fourth year. The emergence of variants with the capacity to dodge immunity and infect even vaccinated individuals is constantly moving the goalposts farther and farther. The COVID-19 virus is likely to persist perhaps indefinitely.
Why can’t the virus be eliminated?
To get rid of any virus, we must be able to block its spread from one person to another. This is easier said than done. Not all viruses are amenable to eradication. In the case of SARS-CoV-2, there are several insurmountable hurdles that stem from the unique biology of the virus, the nature of our immunity to it, the properties of the currently available COVID-19 vaccines and the ease of their access to the entire world.
First, the biology of SARS-CoV-2 makes it particularly recalcitrant to eradication. Infected individuals are not easy to identify because many people infected by SARS-CoV-2 don’t display any symptoms and appear healthy (asymptomatic) – but transmit the virus (contagious) to people around them.
Evidence before the advent of the omicron variant suggests that SARS-CoV-2 infections may be asymptomatic in about 40% of cases. In the case of omicron, the fraction of asymptomatic infections appears to be much higher. Such asymptomatic but contagious individuals can’t be identified and isolated easily. The virus continues to spread to people around them. This represents a big hurdle in interfering with transmission of the virus among people in a community.
While it is known that SARS-CoV-2 can infect many animals as well, we still don’t know which one (or more) of them may serve as reservoirs of the virus, to sustain transmission among humans. Because these animal reservoirs are unknown, eliminating the virus by culling such animals is not feasible.
Additionally, SARS-CoV-2 has manifested an unexpected ability to shape-shift into newer versions. It emerged in late 2019 in Wuhan and spread rapidly around the world, with the parental variant evolving over the next several months into multiple other variants in different geographic locations. Most of 2021 was dominated by news of the alpha, beta, gamma and delta variants displacing the initial strain.
The highly infectious omicron variant, endowed with the ability to overcome immunity, was first detected in late 2021. The emergence of omicron represents a significant mutational jump by SARS-CoV-2. Since then, omicron and its sub-variants (more than 300 of them) have been driving the pandemic around the world for a year now.
Secondly, our immunity to respiratory infections is not very durable. SARS-CoV-2 has proved this to be the case. The immunity we gained by falling sick or getting vaccinated has turned out to be transient, lasting only a few months, particularly against infection. The currently available COVID-19 vaccines are good at providing lasting protection against potentially fatal COVID-19 but are woefully inadequate at protecting against infection and spread. They are not capable of blocking virus transmission.
That is why, despite high levels of full vaccine coverage (in developed countries), the world has been reporting breakthrough infections accompanying the emergence of variants, particularly the delta and the omicron. Seeking to overcome this with repeated booster shots can help mitigate COVID-19 severity but certainly won’t eradicate the virus.
Finally, global vaccination coverage is far from ideal, especially in low- and middle-income countries. At this time, approximately 5.5 billion people around the world have been fully vaccinated. Country-wise full vaccine coverage varies widely, from more than 80% in several developed countries to under 25% in African countries.
With about 30% of the world’s population yet to receive their first vaccine dose, global vaccination rates have slowed. At the current rate of about 1.4 million vaccine doses a day, and assuming it does not come down further, it will take us until the end of 2027 to administer at least one dose to the remaining 2.5 billion unvaccinated people of the world.
Multiple reasons are responsible for inadequate vaccine coverage, with the predominant ones being inequitable access (arising from vaccine nationalism, subpar supply chains, poor health investment and lack of public health infrastructure) and vaccine hesitancy, among others. Clearly, the prospect of ending or, more realistically, stemming the pandemic through worldwide vaccination is bleak.
A likely trajectory
Economically developed countries may succeed in taming the pandemic with periodically updated booster shots and antiviral drugs. But in an interconnected world, these countries will have to face the continued risk of reintroduction of the virus from regions with low vaccine coverage and poor public health measures.
It is quite evident, then, that eradicating SARS-CoV-2 is an unrealistic goal. With this in mind, how is the pandemic going to play out in future?
Scientists need to take several parameters into account when attempting to answer this question. They include the daily case-load, the number of daily deaths, the emergence of variants, their transmissibility and ability to overcome immunity, the frequency of outbreaks, vaccination rates and the availability of effective antiviral therapy, among others.
Many of these parameters are interlinked, and arriving at meaningful conclusions would be a highly challenging task. This is further complicated by the lack of the relevant data, of comparable quality, from many countries.
Consideration of several factors, such as the inability of the current COVID-19 vaccines to block virus transmission, the temporary nature of immunity against infection, the high transmissibility of the variants (particularly delta and omicron), incomplete vaccine coverage around the globe, the existence of unknown animal reservoirs of the virus and the lack of a concerted and coordinated global effort to combat the pandemic have collectively led many scientists to a consensus opinion about the pandemic’s future course.
According to this, the pandemic, which currently appears to be declining, may eventually ‘stabilise’, with the number of infections staying more or less constant over the years with occasional, perhaps seasonal, flare-ups. At this point, according to scientists, COVID-19 will have transitioned from its pandemic phase to the endemic phase, representing a kind of uneasy truce between the virus and the world.
‘Endemic’ means the consistent presence of a disease in a region or community at a certain ‘baseline level’. Achieving endemicity doesn’t necessarily mean we don’t have to worry about COVID-19. For example, the flu is no longer a pandemic: data from the US shows that it still kills up to 52,000 people a year! Official figures also suggest that dengue and tuberculosis are reported to have killed about 40,000 people in 2017 and 79,000 people in 2019, respectively, in India.
The WHO declared COVID-19 to be a “pandemic” after it had spread to 114 countries, affecting more than 118,000 people and killing 4,291 people, on March 11, 2020. The WHO may perhaps declare its end when it is certain that the world has reached a stage at which the transmission and the evolution of SARS-CoV-2 have been significantly limited worldwide.
Reaching this stage will be contingent on countries’ renewed focus on equitable access to vaccines and drugs, responsive public health plans and the implementation of policies to protect the vulnerable.
As we near the end of the third year of the pandemic, we have no clear-cut answers about how and when the pandemic will end. Hopefully, it will not be the plague it has been thus far, as it transitions to the endemic phase.
At the same time, we will not be able to tell if we have made this transition until much later after it has actually taken place. All we can say for sure right now is that the pandemic is poised to start its fourth year.
S. Swaminathan is a retired scientist based in Hyderabad. The views expressed here are his own.