Kasauli : There has been zero rejection of Covid-19 vaccine out of over 1,000 batches that underwent quality testing before their market release since January this year, said experts involved in the exercise at the country’s only government vaccine testing laboratory at the Central Drugs Laboratory (CDL) in Himachal Pradesh’s Kasauli, adding that the results should help instil confidence in people regarding the quality of indigenously manufactured jabs against the coronavirus disease.

The lab, which tests 22 vaccines in all, has noted a 0.2% general rejection rate for vaccines during quality testing.

“We haven’t rejected any samples of Covid-19 vaccines on account of not meeting quality standards so far. We do batch-wise testing for potency, sterility, biochemical or abnormal toxicity etc before approval is given for release in market for commercial use. The samples for testing from ready batches are provided by the manufacturer,” said Dr Arun Bhardwaj, director, CDL in Kasauli.

Data shared by CDL Kasauli show that till November 23, a total of 1,049 batches of Covid-19 vaccine have been released comprising approximately 1,521 million vaccine doses.

“Zero rejection rate during quality testing speaks volumes about the quality of Covid vaccines being manufactured in the country; and that also should take care of any vaccine related hesitancy in the minds of people,” said Dr S Eswara Reddy, joint drugs controller, Central Drugs Standard Control Organisation.

The latest batch that the laboratory cleared was of Zydus Healthcare’s anti Covid-19 vaccine, ZyCoV-D. According to Bhardwaj, seven batches of ZyCoV-D with total of 237,530 doses have been cleared for market release so far.

“We are mandated to establish safety, efficacy, and quality of vaccines. Rejection of vaccine samples for pre-release quality testing is a rare occurrence anyway; in terms of percentage the rate of rejection would be around 0.2%, which is minuscule. However, if a sample fails quality tests for whatever reasons, then the entire batch from which the sample was taken has to be discarded or recalled if the testing was done based on a complaint regarding the quality of the product,” said Bhardwaj.

Testing currently takes place of six manufacturers of Covid vaccines: Serum Institute of India for Covishield, Bharat Biotech for Covaxin, Zydus Healthcare for ZyCoV-D, Panacea Biotec and Gamaleya Research Institute for Sputnik V, and Biological E for Janssen.

The number of doses in a batch may vary based on the manufacturing capacity of the vaccine manufacturer; for example, a batch of SII’s Covishield vaccine would have around four million doses, and a batch of Bharat Biotech’s Covaxin vaccine would have anywhere around 400,000-800,000 doses.

Since testing is a destructive process and vials that are tested for quality cannot be reused; therefore, testing of all vials in a batch is not possible.

“Vials are picked up randomly from each batch for testing, and only after each of the batches clear quality test, the company is provided a certificate that allows the product to be released in market for commercial use,” said Bhardwaj.

In case a sample fails the quality test, the manufacturer is intimated and invited over to CDL for another round of testing.

“The manufacturer personally witnesses another round of quality testing that is conducted to substantiate the results of round one. If the sample fails again then the manufacture is made to sign a document and asked to investigate the root cause,” he added.

The central lab usually tests at least 7,000 batches in a year of different vaccines, including those that are imported into the country, for quality.

“This year we will most likely be touching 8,000 batches. This year has been busy,” said Sushil Kumar Sahoo, deputy assistant director, CDL, Kasauli.