A COVID-19 vaccine candidate should show at least 50 per cent efficacy during the third phase of clinical trials for it to be widely deployed, according to an advisory for vaccine development issued by the central drug authority.

According to the Central Drugs Standard Control Organization (CDSCO), people with a history or laboratory evidence of prior novel coronavirus infection should be allowed to participate in trials if they did not have acute COVID-19 or other acute infectious illness.

The advisory ‘Regulatory Guidelines for Development of Vaccines with Special Consideration for COVID-19 Vaccine’ have been uploaded on the CDSCO’s website. It is seeking comments and feedback from the public until October 12.

“To ensure that a widely deployed COVID-19 vaccine is effective, the primary efficacy endpoint point estimate for a placebo-controlled efficacy trial should be at least 50 per cent and the statistical success criterion should be that the lower bound of the appropriately alpha-adjusted confidence interval around the primary efficacy endpoint point estimate is (greater than) 30 per cent,” the guidelines said.

Considering the urgent need for a safe and effective vaccine for the prevention of COVID-19, clinical development programs of COVID-19 vaccine may proceed through an adaptive and seamless approach.

“However, as applicable for any vaccine, regardless of whether clinical development programs proceed in discrete phases with separate studies or via a more seamless approach, an adequate data, including data to inform the potential risk of vaccine-associated Enhanced Respiratory Disease (ERD) will be needed,” it added.

Consideration may be needed for conducting more than one vaccine efficacy trial in case different subtypes of a pathogen are involved, the guidelines underlined.

In such cases, the efficacy trials may be required to be conducted in different regions where certain subtypes are known to predominate. It is anticipated that adequately powered efficacy trials for COVID-19 vaccines will be of sufficient size to provide an acceptable safety database for younger adult and elderly populations, provided that no significant safety concerns arise during clinical development that would warrant further pre-licensure evaluation.

According to the CDSCO guidelines, as it is possible that a COVID-19 vaccine “might be much more effective in preventing moderate to severe versus mild COVID-19”, consideration should be given for powering efficacy trials for formal hypothesis testing on a severe COVID-19 endpoint.

Evaluation of vaccine safety and efficacy in phase III clinical trial in adults should include adequate representation of elderly individuals and individuals with comorbidities, they said. Further, productive and developmental toxicity data should be there as per the requirements specified in the New Drugs and Clinical Trials Rules, 2019 to support the inclusion of pregnant women and women of childbearing potential, they added.

It is important for COVID-19 vaccines to plan for pediatric assessments of safety and effectiveness considering the pandemic in accordance with the New Drugs and Clinical Trials Rules, 2019. After approval of a vaccine, it is essential to monitor vaccine safety in routine use, the guidelines underscored.

All vaccines are required to be characterised and manufactured in compliance with good manufacturing practices as prescribed in the rules.

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