A universal Covid vaccine is “urgently needed”, scientists have warned after a study confirmed previous infection or vaccination offers only limited protection against new variants of the coronavirus.
Variants such as Delta and Omicron are “genetically distinct” from previous forms and can be transmitted even to people who have been jabbed or have previously had Covid, researchers found.
Covid waves have been driven by the original Covid-19 virus as well as Beta, Delta and Omicron, three variants listed as variants of concern (VOCs) by health authorities.
The team at Columbia University Mailman School of Public Health in New York said their model accurately predicted the trajectories of cases and deaths in most locations they studied, and retrospectively predicted the Delta and Omicron waves before the real-life peak of cases and deaths linked to these VOCs.
The researchers then used their model to estimate the characteristics of each variant, including the infection-detection rates, infection-fatality rates and population susceptibility and transmissibility – before comparing these across the locations analysed.
The estimates were then used to quantify the erosion of immunity and the increase in transmissibility for each VOC.
Study author Dr Wan Yang, assistant professor of epidemiology at the Columbia University Mailman School of Public Health, said: “These repeated pandemic waves have been driven by new VOCs that erode prior immunity from either infection or vaccination and increase transmissibility or a combination of both.
“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.”
A universal vaccine could block infection and prevent severe disease, Dr Wan and co-author Dr Jeffrey Shaman have suggested.
The team found that the Beta variant eroded immunity among 65pc of people previously infected by the original Covid-19 and was 35pc more transmissible in comparison.
Delta estimates varied be- tween the locations, but the scientists said the variant eroded immunity from previous infection or vaccination by about 25pc and was 50pc more transmissible, while Omicron eroded immunity from previous infection or vaccination by 55pc and was roughly 95pc more transmissible.
Previous immunity to Covid-19 does not preclude outbreaks caused by new VOCs, the team concluded. They added that neither previous infection nor vaccination completely blocks infection from new variants.
The authors of the study, published in the journal eLife, said this meant a “universal vaccine that can block SARS-CoV-2 infection, and prevent severe disease, is urgently needed”.
Efforts to design a universal vaccine that would remain effective in the face of frequent mutations have so far proved largely fruitless. However, researchers in the UK last month hailed a “promising” breakthrough in the race to develop a “holy grail” vaccine that can offer protection against multiple Covid variants and a variety of common colds caused by other coronaviruses.
Scientists at the Francis Crick Institute in London believe they have identified a genetic feature of Sars-CoV-2 that appears to be “similar” across a number of coronaviruses and is less prone to mutations, making it a potential target for a pan-coronavirus, or universal, vaccine.