India's COVID-19 vaccine Covaxin, developed by Bharat Biotech in collaboration with the Indian Council of Medical Research, effectively neutralises both Alpha and Delta variants of coronavirus, according to the US National Institute of Health (NIH).
Results from two studies of blood serum from people who had received Covaxin suggest that the vaccine generates antibodies that effectively neutralise the B.1.1.7 (Alpha) and B.1.617 (Delta) variants of SARS-CoV-2, first identified in the UK and India, respectively, the NIH said.
NIH further said that an adjuvant developed with its funding has contributed to the "success of the highly efficacious Covaxin", which roughly 25 million people have received to date in India and elsewhere.
Adjuvants are substances formulated as part of a vaccine to boost immune responses and enhance a vaccine’s effectiveness.
Covaxin contains a disabled form of SARS-CoV-2 that cannot replicate but still stimulates the immune system to make antibodies against the virus.
The vaccine is safe and well-tolerated, according to the published results from a Phase 2 trial. The safety data from a Phase 3 trial of Covaxin will become available later this year, the NIH further said.
Adjuvant in Covaxin: How Does It Work?
The adjuvant used in Covaxin - Alhydroxiquim-II - has been developed by ViroVax of Lawrence, Kansas, with support exclusively from the NIAID Adjuvant Development Program.
The adjuvant comprises a small molecule attached in a unique way to Alhydrogel, a substance frequently called alum that is the most commonly used adjuvant in vaccines for people, the NIH said.
Alhydroxiquim-II travels to lymph nodes, where the small molecule detaches from alum and activates two cellular receptors.
These receptors, TLR7 and TLR8, play a vital role in the immune response to viruses, it added.
Covaxin Efficacy Against Variants
Alpha, Beta, Gamma and Delta are the four variants of concern of COVID-19, with with Delta Plus being a sub-lineage of the Delta variant which is also a variant of concern.
Last week, the Centre had said that Covishield and Covaxin work against Alpha, Beta, Gamma and Delta variants, while the effectiveness tests against the Delta Plus variant is ongoing.
Covaxin is effective against the Delta variant, but the antibody response is slighly reduced. There is a three-fold reduction against this strain, Indian Council of Medical Research Chief, Dr Balram Bhargava, said.
With Pfizer and Moderna Covid vaccines, there is a seven-fold reduction.
Meanwhile, the neutralizing capablity of Covaxin does not change with the Alpha variant, the Centre said.