An adjuvant developed with funding from the National Institutes of Health (NIH) has contributed to the success of the highly efficacious COVAXIN COVID-19 vaccine, 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 was developed and is manufactured in India, which is currently suffering a devastating health crisis due to COVID-19.
The adjuvant used in COVAXIN, Alhydroxiquim-II, was discovered and tested in the laboratory by the biotech company ViroVax LLC of Lawrence, KS, 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. 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. Alhydroxiquim-II is the first adjuvant in an authorized vaccine against an infectious disease to activate TLR7 and TLR8. In addition, the alum in Alhydroxiquim-II stimulates the immune system to search for an invading pathogen.
Molecules that activate TLR receptors stimulate the immune system powerfully, but the side effects of Alhydroxiquim-II are mild. This is because, after COVAXIN is injected, the adjuvant travels directly to nearby lymph nodes, which contain white blood cells that play an essential role in identifying pathogens and fighting infection. Consequently, only a small amount of Alhydroxiquim-II is needed in each dose of vaccine, and the adjuvant does not circulate throughout the body, thereby averting more widespread inflammation and undesirable side effects.
COVAXIN comprises a disabled form of SARS-CoV-2 that cannot replicate but still stimulates the immune system to make antibodies against the virus.
Safety data from a Phase 3 trial of COVAXIN in 25,800 participants in India will become available later this year. Meanwhile, unpublished interim results from the Phase 3 trial indicate that the vaccine has 78% efficacy against symptomatic disease, 100% efficacy against severe COVID-19, including hospitalization, and 70% efficacy against asymptomatic infection with SARS-CoV-2, the virus that causes COVID-19.
