Data from a comply with-up to the phase I trials of Bharat Biotech’s Covaxin shows that the immune response to the vaccine generated neutralising antibodies that remained elevated even 3 months just after the receipt of the second dose.
A study by Bharat Biotech and Indian Council of Medical Research published in Lancet Infectious Diseases also noted that there was a greater immune response—both in terms of antibodies and T-cell immunogenicity—when the gap among the two doses of the vaccine was 28 days (the regime followed in the phase 2 trial) as compared to 14 days (the regime followed in the phase 1 trial). Earlier this month, based on interim phase 3 information, Bharat Biotech had reported a 81% efficacy for Covaxin.
The 1st phase of the trial, apart from vaccine immunogenicity and reactogenicity, also looked at adjuvant selection—adjuvants are substances that improve particular immune responses to a vaccine. Based on outcomes from 4 groups administered any one of the four—3 microgram with adjuvant Algel-IMDG, 6 microgram with Algel IMDG, 6 microgram with Algel and 6 microgram of Algel adjuvant alone (the manage group) – Algel IMDG was chosen as the most successful adjuvant.
The 3-month (from second dose of phase 1 trial) also revealed that the T-cell memory response, that has emerged as a metrict for estimating Covid-19 vaccine achievement, was more pronounced of the ‘6 micrograms with Algel-IMDG adjuvant’ candidate. Also, day 56 serum samples from 38 participants in phase 2 trials who belonged to the group injected with this canidate successfully neutralised the UK variant of SARS CoV-2. This was, therefore, preferred more than the ‘3 microgram with Algel IMDG) candidate for phase 3 trials.
While the phase 2 data involved 380 adults and adolescents showed that the most common adverse event was pain at the injection site, and headache, fatigue and fever, a third of the ‘unsolicited’ (reported by the vaccine recipient outdoors the information collected per adverse occasion reporting protocol) adverse events—nine out of 27—were identified to be associated to the vaccine.
Also, against the backdrop of the controversy generated by the grant of the Indian equivalent of ‘emergency use authorisation’ to Covaxin pending phase 3 efficacy information, the study notes that no Covid-19 situations have been reported in the test or manage group in phase 2 and SARS CoV-2 testing of trial participants post vaccination was also not completed in each phase 1 and 2. This would imply the information from the two phases would not have permitted for efficacy assessment.