- If reinfection turns out to be trivial, and if a highly effective vaccine is not given to most of the world’s population, SARS-CoV-2 will likely settle into an endemic pattern.
- A new study estimates that immunity lasts between 5 and 7 months.
- The seasonality of the virus could make it come back every year.
Impossible to anticipate how the health situation will develop as the second wave looms. American researchers from the Columbia Mailman School are interested in knowing whether Covid-19 could become endemic, that is to say, last over time. To do this, they took several factors into account such as the risk of re-infection, 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 result in annual outbreaks of Covid-19. On the other hand, if immunity takes longer to set in, this could lead to the disappearance of the virus but its resurgence after a few years. “If reinfection turns out to be trivial, and if a highly effective vaccine is not given to most of the world’s population, SARS-CoV-2 will likely settle into an endemic model., wrote the researchers. It remains to be seen whether re-infections will be common, how often they will occur, how contagious those re-infected 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 endemic virus. Serological studies indicate that most infections, regardless of their severity, lead to the development of certain antibodies specific to SARS-CoV-2. Yet it is still unclear whether these antibodies themselves are sufficient to provide “sterilizing immunityLong-term to prevent reinfection. An American study published on October 5 in the journal Immunity suggests that immunity to SARS-CoV-2 could last for 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 bypass immunity to reinvent the organism.
Seasonality in question
The researchers also looked at the coinfection side. 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 concurrent respiratory viral infections are not associated with increased severity of the disease. “Although some SARS-CoV-2 co-infections have been documented, there is insufficient data 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 the transmission of the virus and make it more important in winter, as is the case with influenza, once immunity increases.
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