A new study has found that the Delta variant — the strain of the novel coronavirus first identified in India and now dominant across several countries across the world — can evade antibodies that target specific parts of the virus. But the good news is that both doses of vaccines currently available against Covid-19 can provide protection against infection even though a single jab may still leave people vulnerable.
One Shot Needed Even For Those Who Had Covid?
Researchers at the Institut Pasteur in France sought to study how successful antibodies produced by people who were either infected by the novel coronavirus or had received vaccination against it were in neutralising the Alpha, Beta, Delta and a variant similar to the original version of the virus.
Looking at blood samples of 103 people who had been infected with Covid-19, researchers found that the Delta variant was much less affected by the antibodies of those in this group who had not been vaccinated than the Alpha variant, which was first identified in the UK.
However, it was observed that one dose of the vaccine for people who have recovered from Covid-19 provided a significant boost to their immunity against the Delta variant. The inference being that people who have recovered from Covid-19 should get vaccinated to keep other variants at bay.
The researchers also studied a smaller group of 59 people who had received either one or both the doses of the AstraZeneca or Pfizer vaccines. Samples from only 10 per cent of the people who had received one dose of the AstraZeneca or the Pfizer-BioNTech jab were able to counter the Delta and Beta variants in the labortaory. However, for those who had got both their shots, the neutralisation rate was as high as 95 per cent.
Samples from those who had “received one dose of Pfizer or AstraZeneca vaccines barely inhibited variant Delta. Administration of two doses generated a neutralising response in 95 per cent of individuals," said the study published in the journal Nature.
Is A Booster Shot Needed Against Variants?
A recent study by the Indian Council of Medical Research (ICMR) would appear to echo these findings after it concluded that neutralising antibodies against the Delta variant were absent in 58 per cent of the samples of people who had received one shot of the Oxford-AstraZeneca vaccine, which is being administered in India as Covishield. But that margin came down to 16 per cent in those who received both doses.
In the meantime, the US-based Pfizer has applied for authorisation in that country for a third, booster dose of its vaccine to be administered 6-8 months after the second dose, saying it can dramatically bump up antibody levels against the vaccine. However, the US diseases watchdog Centres for Disease Control and Prevention (CDC) and its drug regulator Food & Drug Administration (FDA) have said that they were not considering approvals for a third dose at this stage as two doses of a vaccine were found to provide sufficient protection against the variants that have been so far detected.
How Much More Contagious Is Delta? Where Is It Spreading?
According to reports, after it was first spotted in India in October last year, the Delta variant has quickly jumped shores and is believed to be almost 60 per cent more infectious than the Alpha, or Kent, variant that drove a surge in infections in the UK and Europe earlier this year.
According to a World Health Organisation (WHO) report from earlier this month, the Delta variant has now been reported in 96 countries, including in the UK, where it is now the dominant strain, accounting for over 90 per cent of cases. Recent surges in Southeast Asian countries and in Australia, too, are linked to this variant. Delta also accounts for more than 50 per cent of new cases in the US, the CDC has estimated.