Covid-19 will become – well, it has already become – endemic, which means there will be focal outbreaks. The virus will try to find those who continue to be vulnerable, such as the people who received a vaccine but never had the natural infection. It will continue to be in circulation for quite some time and it is unlikely that it will disappear from the world. It is just that there will be cases that will not be picked up because the symptoms are mild or people do not come forward for testing.
After circulating for several years, however, it might disappear. For any virus that spreads rapidly in the population – the Ro (reproductive number or the number of people a patient can infect) for Covid-19 is very high, more so for the Omicron variants. So the virus will eventually infect the entire population. So even if the virus is in circulation, the probability of finding a susceptible person becomes smaller and smaller. Why it will take years is because there will be a continuing cycle of people whose immunity is waning. Think of it as a water tank, where outflow is high and inflow is a trickle, so eventually it will run out of water.
But could the Sars-CoV-2 virus mutate again and cause large-scale infections?
If you look at the Omicron variant, it was detected in November last year. It has been over ten months now but we haven’t seen a new lineage emerge even though the mutations continue to occur. What this means is that the virus is coming close to stabilisation – it doesn’t need to remain very aggressive because it has achieved the fitness it requires to survive.
We may perhaps not see a variant that is very dangerous at this point of time. With Omicron, we have seen that it causes milder infections, fewer hospitalisations and deaths.
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What is likely to happen to the virus in the future?
As for the future of the virus, if you look at the phylogenetic tree of Sars-CoV-2 – a mapping of the virus’ mutation that can tell us which the closest relative of a variant is – the genetic distance between Omicron and the earlier variants is pretty big. Omicron is becoming like a cousin, it is still in the family but quite distant. As Omicron has replaced the other variants, if a new variant does emerge, it will be far away from the original virus. So, would it then belong to the Sars-CoV-2 or be a whole new family?
We do not know for sure, but the way it is drifting – even within the Omicron family, you will see that the drift is far stronger between say BA.1, BA.2, BA.4 and BA.5 than what we were witnessing earlier – the mutations are putting the virus at the brink.
The other reason why I feel that the virus may change into a new one is because there is sufficient evidence to show that for Sars-CoV-2 there is sufficient evidence of reverse zoonosis (spreading back to animals from humans). The virus continues to have reservoirs in animals – even household rodents – so the possibility of transmitting back to humans can never be ruled out. That will, however, lead to different mutations that could be beyond Sars-CoV-2. It will remain in the coronavirus family only, of course.
Now that we are in the endemic phase of the disease, do we still need to continue wearing masks, taking booster shots?
All those who are at a risk of developing severe disease because of age or comorbidities should get a booster dose. However small the risk may be with Omicron, why not keep yourself protected? You should also continue to wear masks in crowded places.
Those who haven’t had a natural infection, those who do not elicit enough response through vaccination, or those who have waning immunity, must continue to wear masks in closed spaces with a large number of people.
While deciding on their level of protection, people must keep in mind that even though Omicron might cause a mild infection, they might get a post-Covid syndrome. The risk of post-Covid complications is almost half in cases of mild infection but we still do not clearly know what will be the long term impacts on the organs.
How long should we continue to take booster doses? And what will be the role of a newer generation of vaccines that either protects against all variants of Sars-CoV-2 or against any of the sarbecoviruses like SARS?
A pan-sarbecovirus vaccine is perhaps the best thing that could happen. These efforts have been intensified; there is now increasing use of artificial intelligence that can predict which epitopes will be able to protect you against all. If you take this one, it is possible that the protection will also be longer.
It is difficult to say if the current vaccine would be needed every year. But clearly giving it four or five times hasn’t yielded all that much success in reducing the frequency of the infection. However, severe disease and hospitalisation remain low.
Why Dr Gangakhedkar?
Dr R R Gangakhedkar is the former head of epidemiology and communicable diseases at the Indian Council of Medical Research (ICMR). He led the country’s fight against Covid-19 in the early days of the pandemic. He is also a member of the World Health Organisation’s Scientific Advisory Group for the origin of novel pathogens.