How long will the public health and global economy be threatened by the Covid-19 pandemic? We still don’t have the answer. Without the vaccine, experts predict the impact of the disease could last for several years.
When Covid-19 ends is still a big question for many reasons, which largely depend on human actions both individually and collectively. However, scientists hope to unravel the mystery of the SARS-CoV-2 virus and how it interacts with the human body to predict when the pandemic will end soon.
When does community immunity be achieved?
If immunity lasts 2 years or longer, Covid-19 may disappear gradually after a few years. If this capability only lasted for a year, Covid-19 could come back and rage more violently until an effective vaccine is put into widespread use.
Currently, there are many different types of vaccines in the world, but their effectiveness still needs to be considered. Moreover, manufacturers will have to make great efforts to produce enough vaccines to meet the needs of the community. In this context, immunity is the key to understanding how long a pandemic will last and scientists are trying to decipher this mystery.
Without a vaccine, scientists believe it is necessary to develop community immunity to end the disease. Researchers have come up with some simple maths that explain how many people need immunity to the virus so the pandemic can stop itself.
Accordingly, the outbreak of disease ends when each new case, on average, infects less than 1 person. Immunity can help us achieve this.
If each case infected, on average, infected 2 people, then half of the population will need to be immune to the virus for the disease to disappear naturally.
If each case is transmitted to 3 others, 2/3 of the population needs to develop immunity.
For Covid-19, the identification was very complicated. The baseline infection rate (RO) of SARS-CoV-2 virus determines how many people a person can infect is not a fixed number. It can vary in different environments and communities, as well as depending on whether people follow the instructions for wearing a mask or washing their hands.
Moreover, not everyone is equally at risk of contracting the virus. Theoretically, the end of the epidemic could be reached a little earlier if all the most vulnerable, the most susceptible and contagious people first developed immunity.
The researchers estimated that the RO coefficient of the SARS-CoV-2 virus was between 2 and 3. And so the virus will continue to spread until about half to three-quarters of the population grows. immune. When community immunity forms, the number of new infections will decrease.
However, community immunity can only be built effectively if the immunity lasts. If the immune system is weakened then the virus is at risk of coming back, growing stronger and spreading further.
Potential risks
Ideally, community immunity will grow slowly in the population to avoid overcrowding the health system, avoid creating chaos and lead to more severe loss of life and property. .
Recently, epidemiologists at Harvard University have published a scientific study assessing the time it takes to achieve community immunity. They have modeled the approach by which countries continue to adopt social-gap measures in the form of stop-and-repeat iterations to control disease. "We realize that with this model, it may take until 2022 to establish community immunity sufficient for the virus to stop working."
Next, how long does it take to strengthen the public health care capacity in parallel with the relaxation of restrictive measures? The researchers concluded: "It will be difficult to return to normal life if we do not have the vaccine."
Some have advocated a way to promote faster community immunity in the hope of achieving results by 2022. This means that the number of cases and deaths in general will increase. spurt (ie about 0.5% to 0.8% of people with Covid-19 will die).
"Obviously, the epidemic ends only when community immunity is formed, but if" floating ", you tend to exceed the necessary number and a larger proportion of the population will become ill." said Tedijanto, a researcher at Harvard University’s research group.
In their New York Times article, biologists Natalie Dean and Carl Bergstrom calculated the damage if no control measures were taken: “If 100,000 people get sick at the peak of the epidemic and each person spreading to 0.9 people, there will be an additional 90,000 new cases even more. If the disease is not controlled in the US, it will continue for months after the community immunity is formed. With this scenario, by the time the pandemic ends, the number of people infected may exceed the threshold needed to create immunity, said biologist Natalie Dean.
"Even if the epidemic spreads in a calculated way to achieve community immunity, the number of deaths is really shocking," he added. Thus, other solutions need to be considered. ”
Will have to live permanently with the disease?
"If the immunity lasts a year or less, we can predict that the disease will break out in the winter every year until the vaccine is found. If the immune system lasts longer, from 1 to 5 years, there will be sporadic outbreaks every few years. In short, the longer the immune system is, the more likely it is that the disease will diminish and eventually disappear by itself, ”said Stephen Kissler, a researcher at Harvard University.
At present, there are many reasons that scientists still cannot explain why human immunity never weakens before some diseases. For smallpox, for example, many people have lifelong immunity. According to the researchers, antibodies that protect the body against smallpox attack can be found about 88 years after vaccination.
In contrast, for different corona virus strains, the antibody may weaken over a few years. But according to scientists, even if a person loses those antibodies does not mean that they are susceptible to re-infection.
Currently, studies show that almost all patients with Covid-19 develop antibodies to SARS-CoV-2 and T cells (or T lymphocytes). T cells are one of the important components of the immune system, helping to identify harmful viruses and bacteria when these pathogens enter the body.
However, more research is still needed to see how far antibody development can take place in order to achieve the longest lasting immunity. Of course, this will be very time consuming.
“The worst scenario I can imagine is that people with Covid-19 who have mild or asymptomatic symptoms will not develop much immunity and the virus will quietly creep into every corner of the world, then caused a major outbreak, ”said Kissler.
So will this mean we will have to live in blockades until at least 2022? "We can still be a bit optimistic at this point," Tedijanto said. There is no single bullet to defeat Covid-19. But by incorporating a variety of preventive measures such as wearing a mask, better communicating information about hot spots and ways to avoid these hot spots, increasing testing, monitoring patient contact, we can limit the spread of infection and help life return to normal to some degree. This will be a long-term process, requiring patience. And it is important that we are prepared to live with the SARS-CoV-2 virus. ”
