Published: Published Date – 03:30 PM, Wed – 10 August 22
New York: There is a need for a universal vaccine that can block SARS-CoV-2 infection as well as prevent severe disease from emerging Covid waves in the future, researchers have suggested.
Writing in the journal eLife, the team from Columbia University in the US highlighted the need for more proactive planning and preparedness as different variants of concern (VOCs) evade — the original (or ancestral) SARS-CoV-2 virus, Beta, Delta and Omicron — the effect of both vaccinations and prior infections.
“These repeated pandemic waves have been driven by new VOCs that erode prior immunity from either infection or vaccination, increase transmissibility, or a combination of both,” explained Wan Yang, Assistant Professor of Epidemiology at the University’s Mailman School of Public Health.
“Although laboratory and field studies provide insights into variant epidemiological characteristics, quantifying the extent of immune erosion and changes to transmissibility for each VOC is challenging,” Yang said.
To better understand the characteristics of the different Covid-19 VOCs, the team developed a mathematical model using weekly case and death data from nine South African provinces, from March 2020 to end of February 2022, to reconstruct SARS-CoV-2 transmission dynamics.
They found that the Beta variant eroded immunity among roughly 65 per cent of people previously infected with ancestral SARS-CoV-2 and was 35 per cent more transmissible than the original virus.
Estimates for Delta varied between provinces, but overall the variant eroded immunity from prior infection or vaccination by roughly 25 per cent and was 50 per cent more transmissible. This aligns with a reported 27.5 per cent reinfection rate seen during the Delta wave in Delhi, India.
Finally, for Omicron, estimates varied but consistently highlighted its known higher transmissibility than previous VOCs. The researchers estimated that Omicron was roughly 95 per cent more transmissible than ancestral SARS-CoV-2 and eroded immunity by 55 per cent (prior infections and vaccinations).
These results illustrate that high prior immunity to SARS-CoV-2 does not preclude new Covid outbreaks, as neither prior infection nor current vaccination completely block infection from a new variant.
Multiple SARS-CoV-2 variants of concern and interest have emerged in the two years since the pandemic began, and it is challenging to predict the frequency and direction of future viral mutation, especially the levels of immune erosion, changes in transmissibility and innate disease severity, said the researchers.
They added that so far, VOCs except Alpha produced some degree of immune erosion, and later VOCs like Delta and Omicron are more genetically distinct from previous variants, making them more capable of causing re-infection despite diverse prior exposure and vaccination.
Given this pattern, the researchers suggest a universal vaccine that can block SARS-CoV-2 infection, and prevent severe disease, is urgently needed.