Delta variant more infectious than Wuhan strain, study finds
A new study from the UK has found that the Delta strain of COVID-19 is eight times less sensitive to vaccine antibodies than the original Wuhan strain.
The study also found that changes to the spike protein in the Delta variant improved its ability to replicate and enter cells, in comparison to the Kappa variant.
The authors say this might explain how the Delta strain has become the most dominant variation of the disease.
The study, published in the journal Nature, compared the mutated Delta variant against the mutated Wuhan-1 variant which was used to develop the vaccines.
The team, led by Ravindra Gupta, a professor of clinical microbiology at the Cambridge Institute of Therapeutic Immunology and Infectious Disease, also analysed infections of 130 healthcare workers across three hospitals in Delhi, India, over six weeks.
Though each of the workers studied had received both doses of the AstraZeneca vaccine, the researchers found that the vaccine was less effective against the Delta variant than other variants.
“By combining lab-based experiments and epidemiology of vaccine breakthrough infections, we’ve shown that the Delta variant is better at replicating and spreading than other commonly-observed variants,” Professor Gupta said.
Joint senior author Dr Patha Rakshit from the National Centre for Disease Control, Delhi, India, said: “The Delta variant has spread so widely to become the dominant variants worldwide because it is faster to spread and better at infecting individuals than most other variants we’ve seen.
“It is also better at getting around existing immunity - either through previous exposure to the virus or vaccination - though the risk of moderate to severe disease is reduced in such cases.”
Professor Anurag Agrawal from the CSIR Institute of Genomics and Integrative Biology, Delhi, India and joint senior author said the infection of healthcare workers with the Delta variant could have severe consequences.
“Although they themselves may only exhibit mild COVID, they risk infecting individuals who have suboptimal immune responses to vaccination due to underlying health conditions - and these patients could then be at risk of severe disease,” Professor Agrawal said.
With their findings, Gupta and his colleagues say we will need to develop strategies for boosting the effectiveness of vaccines against variants of COVID-19.
“We urgently need to consider ways of boosting vaccine responses against variants among healthcare workers,” Professor Agrawal added.
“[This research] also suggests infection control measures will need to continue in the post-vaccine era.”