Why vaccinated people largely escaped the worst of Delta surge? Study explains
The Delta variant of the coronavirus is believed to be highly transmissible and resistant to vaccines. But, a new study has claimed that the strain, which led the second wave of the coronavirus disease (Covid-19), is not able to evade the antibodies generated by vaccination.
The study has been conducted by researchers at Washington University School of Medicine in the United States and published in the journal Immunity.
Delta was declared as the variant of concern by the World Health Organization (WHO).
Why vaccinated people largely escaped the worst of Delta surge?
The researchers analysed a panel of antibodies generated by people in response to Pfizer's Covid-19 vaccine and found that Delta was unable to evade all but one of the antibodies they tested.
Other variants of concern, such as Beta, avoided recognition and neutralisation by several of the antibodies, they said.
"The fact that Delta has outcompeted other variants does not mean that it's more resistant to our antibodies compared to other variants," said co-senior author Jacco Boon, an associate professor at Washington University.
The health experts extracted antibody-producing cells from three people who had received the Pfizer vaccine.
They grew the cells in the laboratory and obtained from them a set of 13 antibodies that target the original strain which began circulating last year.
The researchers tested the antibodies against four variants of concern: Alpha, Beta, Gamma and Delta.
Twelve of the 13 recognised Alpha and Delta, eight recognised all four variants, and one failed to recognise any of the four variants. Out of these, five antibodies neutralised the original strain.
"In face of vaccination, Delta is relatively a wimpy virus. If we had a variant that was more resistant like Beta but spread as easily as Delta, we would be in more trouble," Ellebedy said.
The length and breadth of antibodies
In previous studies, researchers have shown that both natural infection and vaccination elicit lasting antibody production.
But this time, the group of scientists from Washington University noted that the length of the antibody response is only one aspect of protection, and breadth matters too.
An ideal antibody response includes a diverse set of antibodies with the flexibility to recognise many slightly different variants of the virus, said the researchers.
They added that breadth confers resilience, adding that even if a few antibodies lose the ability to recognise a new variant, other antibodies in the arsenal should remain capable of neutralising it.