Who are 'highly protected' against Delta variant of Covid? ICMR study reveals
Those who have recovered from Covid and have got either one or two doses of Covid-19 vaccine have the maximum protection against the Delta variant of SARS-CoV-2 Vitus, an Indian study conducted by the scientists from the Indian Council of Medical Research, National Institute of Virology, Department of Neurosurgery, Command Hospital (Southern Command), Armed Forces Medical College, Pune, has revealed. The study was only on the impact of Covishield.
In the study, the immune response of 5 categories of people was evaluated-
1. One dose vaccinated
2. Two-dose vaccinated
3. Covid recovered plus one dose vaccinated
4. Covid recovered plus two doses vaccinated.
5. Breakthrough cases, which mean infection after one or two doses of vaccination.
The findings suggest that breakthrough cases and the cases where Covid-19 recovered individuals received one of two doses of vaccine have relatively higher protection against Delta variant in comparison with those who have never been infected but got either one or two doses of the vaccine.
"Prior vaccination results in less severe disease against subsequent infection provide evidence that both humoral and cellular immune response play an important role in protection," the study said.
The study also mentions Delta Plus (AY.1), the new variant of Delta, which has been reported from India and many other countries.
Explaining how variants might impact the efficacy of vaccines, the study said, "The worldwide endeavour of scientists to create a safe and effective COVID19 vaccine has resulted in the availability of 18 vaccines, which have received Emergency Use Authorization. The vaccines available against SARS-CoV-2, have shown efficacy ranging from 51 % to 94% against the original strain D614G in phase 3 clinical trials. Immune response to SARS-CoV-2 infection involves innate immune activation and antigen-specific responses of B and T cells. Particularly, the questions about the immune escape of, newly emerging VOCs in vaccinated individuals are still being explored. For example, the efficacy of AZD1222, which was reported to be 70% in the UK and Brazil, only reached 22% in South Africa."
Those who have once been infected are supposed to develop natural antibodies, for which the government has suggested that they should delay their vaccination. But the study reveals that the natural protection can be augmented by even one dose of vaccine against the Delta variant.
"Long-term follow-up of participants could help understand the impact of natural infection and vaccination on long-term protection from SARS-CoV-2 offered by Covishield. It is important to track the breakthrough infections to look for unexpected changes. Monitoring of breakthrough infection would make us understand the impact of new variant or VOC on the escape of vaccine-induced immunity. Data has shown again and again that if the individuals get infected post-vaccination, had been protected from severe disease," the study said.
(With PTI inputs)