What is the shelf life of COVID-19 vaccines?
India administered COVID-19 vaccine doses to over 40 lakh teenagers on Monday—the first day of the inoculation drive for children aged 15-18 years. However, the campaign met with a controversy as some media reports claimed that "expired" COVAXIN vials were used for the cohort. The Union Health Ministry has rejected those claims. But what is a vaccine's shelf life and how is it calculated?
What do we mean by shelf life?
Vaccines are complicated mixtures of proteins, carbohydrates, lipids, inactivated virus, or adjuvants. Like other medical products, vaccine constituents also tend to go bad over time due to slow chemical reactions leading to a reduction in efficacy. That is why vaccines come with a date of expiry. The shelf life is decided by the manufacturer and approved by concerned regulatory authorities.
What were the concerns about COVAXIN's expiry?
Political leaders and sections of the public claimed that vaccine batches that were supposed to expire in November were used to inoculate younger people on Monday. However, the government made clear the shelf life of COVAXIN had been extended from nine months to 12 in early November. A similar extension was earlier approved for Covishield, the government added.
'It is absolutely safe'
"It is absolutely safe. See, initially when the vaccines were being produced, the overall shelf-life issues were available only for that period when the studies were being done," said Dr. NK Arora, a top government expert on coronavirus vaccination. "Now, today, with the experience and the time since when the vaccine was produced, the shelf life has been evaluated through various animal studies."
Why was shelf life extended?
Bharat Biotech, the manufacturer of COVAXIN, had last year submitted an application to the drug regulatory body seeking an extension of the jab's shelf life. The approval was given on October 25, 2021, based on "stability data" provided by the firm. This has helped hospitals and centers utilize stocks that were nearing expiry date and avoid vaccine wastage.
How is shelf life of vaccines determined?
The shelf life of vaccines is calculated by storing it at various temperatures and periodically testing its effectiveness, experts say. Typically, the vaccine is injecting into small animals like mice to assess if its ability to generate antibodies against a virus has gone down over time. The duration over which the product remains stable and effective is considered its shelf life.