Researchers suggest that the new SARS-CoV-2 coronavirus can last for several years. The risk of reinfection, the availability and effectiveness of vaccines, potential seasonality and interactions with other viral infections that could modulate the transmission of the virus are all factors that led researchers to imagine that this virus could become endemic, like the flu.
- If reinfection proves trivial, and a highly effective vaccine is not given to most of the world’s population, SARS-CoV-2 will likely settle into an endemicity pattern.
- A new study estimates that immunity lasts between 5 and 7 months.
- The seasonality of the virus could cause it to come back every year.
It is impossible to anticipate how the health situation will evolve as the second wave looms. American researchers from the Columbia Mailman School were interested in whether Covid-19 could become endemic, that is to say last over time. For this, they took several factors into account such as the risk of reinfection, the vaccine, potential seasonality and mutations. They published their article on October 14 in the journal Science.
Immunity between 5 and 7 months
The scenario explored by the researchers anticipates a decrease in one year of immunity against SARS-CoV-2, developed either after a first infection or by a vaccine. This would give annual epidemics of Covid-19. On the other hand, if immunity takes longer to set in, this could lead to the disappearance of the virus but to its resurgence after a few years. “If reinfection proves trivial, and a highly effective vaccine is not given to most of the world’s population, SARS-CoV-2 will likely settle into an endemicity pattern.the researchers wrote. It remains to be seen whether reinfections will be common, how often they will occur, how contagious those reinfected will be, and whether the risk of serious clinical changes with subsequent infection remains to be understood..”
The unknown that surrounds immunity is the factor that prompts researchers to speak of an endemic virus. Serological studies indicate that most infections, regardless of severity, result in the development of certain SARS-CoV-2 specific antibodies. Yet it remains unclear whether these antibodies are themselves sufficient to provide a “sterilizing immunity” in the long term to prevent reinfection. An American study published on October 5 in the journal Immunity suggests that immunity to SARS-CoV-2 could last at least five months and up to seven months after the first infection. Once this period has passed, the virus would be able to weaken or circumvent immunity to reinvent the organism.
The seasonality in question
The researchers also looked at co-infection. The immune response to SARS-CoV-2 can be affected by whether a person is currently or has recently been infected with another virus. Cross-immunity has already been shown through several studies and other work confirms that simultaneous respiratory viral infections are not associated with increased disease severity. “Although some SARS-CoV-2 co-infections have been documented, the data are insufficient to draw conclusions,” the researchers note, however.
Finally, the other avenue explored is that of seasonality. Covid-19 would be more transmissible in winter. Outside the tropics, many common respiratory viruses reappear seasonally at certain times of the year. Environmental conditions can also modulate virus transmission and make it more important in winter, as is the case with influenza, once immunity increases.
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