Covaxin's protection against Covid-19 may last a year

Covaxin's protection against Covid-19 could last 6 to 12 months, Phase-2 trials interim findings show

Earlier, after Phase-1 trials, researchers said that the vaccine candidate has shown long-term antibody and T-cell memory responses 3 months after vaccination

A medic fills a syringe with COVAXIN, an experimental Covid-19 vaccine. Credit: Reuters Photo

Covaxin is capable of generating antibodies that may remain effective against Covid-19 for six to 12 months, interim findings from the Phase-2 trials of Bharat Biotech's Covid-19 vaccine show.

Researchers testing India's first indigenously developed vaccine candidate – BBV152, branded Covaxin - claimed that it has displayed tolerable safety outcomes with enhanced humoral and cell-mediated immune responses in a wide age range ie., volunteers 12 years and above to 65 years and below.

The age range here is significant as other Covid-19 vaccines like Pfizer's were evaluated in participants of 16 years and above age, while AstraZeneca vaccine was on 18 years and above persons.

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COVAXIN is a highly purified, inactivated two-dose SARS-CoV2 vaccine developed by Bharat Biotech in collaboration with the Indian Council of Medical Research and the National Institute of Virology. While Phase-1 clinical trials had commenced in July, the vaccine is presently in Phase 3 efficacy trial, planned on about 26,000 volunteers.

“In a follow-up of the Phase 1 trial, Covaxin produced high levels of neutralising antibodies that remained elevated in all participants three months (at day 104) after the second vaccination. Based on these results, we hypothesize that Covaxin can generate antibodies that may persist for 6-12 months,” said the team of researchers from Bharat Biotech, ICMR, NIV, AIIMS, Nizam's Institute of Medical Sciences, Hyderabad, Jeevan Rekha Hospital, Belagavi and other institutions involved in the project, in a research paper.

In Phase-2, a total of 380 healthy children and adults were randomised to receive two vaccine formulations (n=190 each) with 3 µg with Algel-IMDG and 6 µg with Algel-IMDG. The vaccine was administered on them in a double-blind manner at multiple centres, with two intramuscular doses given four weeks apart.

“No neutralising antibody differences were observed between sexes and across age groups. BBV152 was well tolerated in both dose groups with no serious adverse events,” the investigators stated in the medRxiv preprint paper.

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According to the paper yet to be peer-reviewed, higher neutralising titres (2-fold) was observed in the Phase-2 study than in the Phase-1 study. Titre denotes the concentration level at which an antibody shows its effect.

After two doses, local and systemic adverse reactions observed in both vaccine groups were minimal, and the majority of them were resolved within 24 hours of onset. No serious adverse events were reported in this study.

Covaxin researchers have earlier claimed that the vaccine has shown long-term antibody and T-cell memory responses (3 months after vaccination) in the Phase 1 volunteers.

To date, 194 vaccines, to prevent Covid-19, are under various stages of development. Some such vaccines were given an emergency use authorization